for Journals by Title or ISSN
for Articles by Keywords
help

Publisher: Emerald   (Total: 356 journals)

 A  B  C  D  E  F  G  H  I  J  K  L  M  N  O  P  Q  R  S  T  U  V  W  X  Y  Z  

        1 2 | Last   [Sort by number of followers]   [Restore default list]

Showing 1 - 200 of 356 Journals sorted alphabetically
A Life in the Day     Hybrid Journal   (Followers: 12)
Academia Revista Latinoamericana de Administración     Open Access   (Followers: 2, SJR: 0.178, CiteScore: 1)
Accounting Auditing & Accountability J.     Hybrid Journal   (Followers: 33, SJR: 1.71, CiteScore: 3)
Accounting Research J.     Hybrid Journal   (Followers: 25, SJR: 0.144, CiteScore: 0)
Accounting, Auditing and Accountability J.     Hybrid Journal   (Followers: 27, SJR: 2.187, CiteScore: 4)
Advances in Accounting Education     Hybrid Journal   (Followers: 17, SJR: 0.279, CiteScore: 0)
Advances in Appreciative Inquiry     Hybrid Journal   (Followers: 1, SJR: 0.451, CiteScore: 1)
Advances in Autism     Hybrid Journal   (Followers: 33, SJR: 0.222, CiteScore: 1)
Advances in Dual Diagnosis     Hybrid Journal   (Followers: 46, SJR: 0.21, CiteScore: 1)
Advances in Gender Research     Full-text available via subscription   (Followers: 5, SJR: 0.16, CiteScore: 0)
Advances in Intl. Marketing     Full-text available via subscription   (Followers: 6)
Advances in Mental Health and Intellectual Disabilities     Hybrid Journal   (Followers: 84, SJR: 0.296, CiteScore: 0)
Advances in Mental Health and Learning Disabilities     Hybrid Journal   (Followers: 30)
African J. of Economic and Management Studies     Hybrid Journal   (Followers: 10, SJR: 0.216, CiteScore: 1)
Agricultural Finance Review     Hybrid Journal   (Followers: 1, SJR: 0.406, CiteScore: 1)
Aircraft Engineering and Aerospace Technology     Hybrid Journal   (Followers: 220, SJR: 0.354, CiteScore: 1)
American J. of Business     Hybrid Journal   (Followers: 20)
Annals in Social Responsibility     Full-text available via subscription  
Anti-Corrosion Methods and Materials     Hybrid Journal   (Followers: 11, SJR: 0.235, CiteScore: 1)
Arts and the Market     Hybrid Journal   (Followers: 9)
Asia Pacific J. of Innovation and Entrepreneurship     Open Access   (Followers: 1)
Asia Pacific J. of Marketing and Logistics     Hybrid Journal   (Followers: 8, SJR: 0.425, CiteScore: 1)
Asia-Pacific J. of Business Administration     Hybrid Journal   (Followers: 6, SJR: 0.234, CiteScore: 1)
Asian Association of Open Universities J.     Open Access   (Followers: 1)
Asian Education and Development Studies     Hybrid Journal   (Followers: 6, SJR: 0.233, CiteScore: 1)
Asian J. on Quality     Hybrid Journal   (Followers: 3)
Asian Review of Accounting     Hybrid Journal   (Followers: 2, SJR: 0.222, CiteScore: 1)
Aslib J. of Information Management     Hybrid Journal   (Followers: 32, SJR: 0.725, CiteScore: 2)
Aslib Proceedings     Hybrid Journal   (Followers: 315)
Assembly Automation     Hybrid Journal   (Followers: 2, SJR: 0.603, CiteScore: 2)
Baltic J. of Management     Hybrid Journal   (Followers: 4, SJR: 0.309, CiteScore: 1)
Benchmarking : An Intl. J.     Hybrid Journal   (Followers: 11, SJR: 0.559, CiteScore: 2)
British Food J.     Hybrid Journal   (Followers: 17, SJR: 0.5, CiteScore: 2)
Built Environment Project and Asset Management     Hybrid Journal   (Followers: 15, SJR: 0.46, CiteScore: 1)
Business Process Re-engineering & Management J.     Hybrid Journal   (Followers: 8)
Business Strategy Series     Hybrid Journal   (Followers: 7)
Career Development Intl.     Hybrid Journal   (Followers: 18, SJR: 0.527, CiteScore: 2)
China Agricultural Economic Review     Hybrid Journal   (Followers: 2, SJR: 0.31, CiteScore: 1)
China Finance Review Intl.     Hybrid Journal   (Followers: 6, SJR: 0.245, CiteScore: 0)
Chinese Management Studies     Hybrid Journal   (Followers: 4, SJR: 0.278, CiteScore: 1)
Circuit World     Hybrid Journal   (Followers: 16, SJR: 0.246, CiteScore: 1)
Collection and Curation     Hybrid Journal   (Followers: 11, SJR: 0.296, CiteScore: 1)
COMPEL: The Intl. J. for Computation and Mathematics in Electrical and Electronic Engineering     Hybrid Journal   (Followers: 3, SJR: 0.22, CiteScore: 1)
Competitiveness Review : An Intl. Business J. incorporating J. of Global Competitiveness     Hybrid Journal   (Followers: 5, SJR: 0.274, CiteScore: 1)
Construction Innovation: Information, Process, Management     Hybrid Journal   (Followers: 14, SJR: 0.731, CiteScore: 2)
Corporate Communications An Intl. J.     Hybrid Journal   (Followers: 8, SJR: 0.453, CiteScore: 1)
Corporate Governance Intl. J. of Business in Society     Hybrid Journal   (Followers: 6, SJR: 0.336, CiteScore: 1)
Critical Perspectives on Intl. Business     Hybrid Journal   (SJR: 0.378, CiteScore: 1)
Cross Cultural & Strategic Management     Hybrid Journal   (Followers: 9, SJR: 0.504, CiteScore: 2)
Data Technologies and Applications     Hybrid Journal   (Followers: 330, SJR: 0.355, CiteScore: 1)
Development and Learning in Organizations     Hybrid Journal   (Followers: 8, SJR: 0.138, CiteScore: 0)
Digital Library Perspectives     Hybrid Journal   (Followers: 33, SJR: 0.341, CiteScore: 1)
Direct Marketing An Intl. J.     Hybrid Journal   (Followers: 6)
Disaster Prevention and Management     Hybrid Journal   (Followers: 21, SJR: 0.47, CiteScore: 1)
Drugs and Alcohol Today     Hybrid Journal   (Followers: 148, SJR: 0.245, CiteScore: 1)
Education + Training     Hybrid Journal   (Followers: 24)
Education, Business and Society : Contemporary Middle Eastern Issues     Hybrid Journal   (Followers: 1, SJR: 1.707, CiteScore: 3)
Emerald Emerging Markets Case Studies     Hybrid Journal   (Followers: 1)
Employee Relations     Hybrid Journal   (Followers: 8, SJR: 0.551, CiteScore: 2)
Engineering Computations     Hybrid Journal   (Followers: 3, SJR: 0.444, CiteScore: 1)
Engineering, Construction and Architectural Management     Hybrid Journal   (Followers: 10, SJR: 0.653, CiteScore: 2)
English Teaching: Practice & Critique     Hybrid Journal   (SJR: 0.417, CiteScore: 1)
Equal Opportunities Intl.     Hybrid Journal   (Followers: 3)
Equality, Diversity and Inclusion : An Intl. J.     Hybrid Journal   (Followers: 17, SJR: 0.5, CiteScore: 1)
EuroMed J. of Business     Hybrid Journal   (Followers: 1, SJR: 0.26, CiteScore: 1)
European Business Review     Hybrid Journal   (Followers: 11, SJR: 0.585, CiteScore: 3)
European J. of Innovation Management     Hybrid Journal   (Followers: 25, SJR: 0.454, CiteScore: 2)
European J. of Management and Business Economics     Open Access   (Followers: 2, SJR: 0.239, CiteScore: 1)
European J. of Marketing     Hybrid Journal   (Followers: 21, SJR: 0.971, CiteScore: 2)
European J. of Training and Development     Hybrid Journal   (Followers: 13, SJR: 0.477, CiteScore: 1)
Evidence-based HRM     Hybrid Journal   (Followers: 5, SJR: 0.537, CiteScore: 1)
Facilities     Hybrid Journal   (Followers: 4, SJR: 0.503, CiteScore: 2)
Foresight     Hybrid Journal   (Followers: 8, SJR: 0.34, CiteScore: 1)
Gender in Management : An Intl. J.     Hybrid Journal   (Followers: 20, SJR: 0.412, CiteScore: 1)
Global Knowledge, Memory and Communication     Hybrid Journal   (Followers: 996, SJR: 0.261, CiteScore: 1)
Grey Systems : Theory and Application     Hybrid Journal   (Followers: 1)
Health Education     Hybrid Journal   (Followers: 2, SJR: 0.421, CiteScore: 1)
Higher Education Evaluation and Development     Open Access   (Followers: 4)
Higher Education, Skills and Work-based Learning     Hybrid Journal   (Followers: 50, SJR: 0.426, CiteScore: 1)
History of Education Review     Hybrid Journal   (Followers: 12, SJR: 0.26, CiteScore: 0)
Housing, Care and Support     Hybrid Journal   (Followers: 8, SJR: 0.171, CiteScore: 0)
Human Resource Management Intl. Digest     Hybrid Journal   (Followers: 21, SJR: 0.129, CiteScore: 0)
IMP J.     Hybrid Journal  
Indian Growth and Development Review     Hybrid Journal   (SJR: 0.174, CiteScore: 0)
Industrial and Commercial Training     Hybrid Journal   (Followers: 5, SJR: 0.301, CiteScore: 1)
Industrial Lubrication and Tribology     Hybrid Journal   (Followers: 7, SJR: 0.334, CiteScore: 1)
Industrial Management & Data Systems     Hybrid Journal   (Followers: 7, SJR: 0.904, CiteScore: 3)
Industrial Robot An Intl. J.     Hybrid Journal   (Followers: 2, SJR: 0.318, CiteScore: 1)
Info     Hybrid Journal   (Followers: 1)
Information and Computer Security     Hybrid Journal   (Followers: 22, SJR: 0.307, CiteScore: 1)
Information Technology & People     Hybrid Journal   (Followers: 45, SJR: 0.671, CiteScore: 2)
Innovation & Management Review     Open Access  
Interactive Technology and Smart Education     Hybrid Journal   (Followers: 12, SJR: 0.191, CiteScore: 1)
Interlending & Document Supply     Hybrid Journal   (Followers: 61)
Internet Research     Hybrid Journal   (Followers: 37, SJR: 1.645, CiteScore: 5)
Intl. J. for Lesson and Learning Studies     Hybrid Journal   (Followers: 4, SJR: 0.324, CiteScore: 1)
Intl. J. for Researcher Development     Hybrid Journal   (Followers: 10)
Intl. J. of Accounting and Information Management     Hybrid Journal   (Followers: 9, SJR: 0.275, CiteScore: 1)
Intl. J. of Bank Marketing     Hybrid Journal   (Followers: 9, SJR: 0.654, CiteScore: 3)
Intl. J. of Climate Change Strategies and Management     Hybrid Journal   (Followers: 17, SJR: 0.353, CiteScore: 1)
Intl. J. of Clothing Science and Technology     Hybrid Journal   (Followers: 8, SJR: 0.318, CiteScore: 1)
Intl. J. of Commerce and Management     Hybrid Journal   (Followers: 1)
Intl. J. of Conflict Management     Hybrid Journal   (Followers: 15, SJR: 0.362, CiteScore: 1)
Intl. J. of Contemporary Hospitality Management     Hybrid Journal   (Followers: 14, SJR: 1.452, CiteScore: 4)
Intl. J. of Culture Tourism and Hospitality Research     Hybrid Journal   (Followers: 20, SJR: 0.339, CiteScore: 1)
Intl. J. of Development Issues     Hybrid Journal   (Followers: 9, SJR: 0.139, CiteScore: 0)
Intl. J. of Disaster Resilience in the Built Environment     Hybrid Journal   (Followers: 6, SJR: 0.387, CiteScore: 1)
Intl. J. of Educational Management     Hybrid Journal   (Followers: 6, SJR: 0.559, CiteScore: 1)
Intl. J. of Emergency Services     Hybrid Journal   (Followers: 8, SJR: 0.201, CiteScore: 1)
Intl. J. of Emerging Markets     Hybrid Journal   (Followers: 4, SJR: 0.474, CiteScore: 2)
Intl. J. of Energy Sector Management     Hybrid Journal   (Followers: 2, SJR: 0.349, CiteScore: 1)
Intl. J. of Entrepreneurial Behaviour & Research     Hybrid Journal   (Followers: 5, SJR: 0.629, CiteScore: 2)
Intl. J. of Ethics and Systems     Hybrid Journal   (Followers: 3, SJR: 0.333, CiteScore: 1)
Intl. J. of Event and Festival Management     Hybrid Journal   (Followers: 7, SJR: 0.388, CiteScore: 1)
Intl. J. of Gender and Entrepreneurship     Hybrid Journal   (Followers: 7, SJR: 0.445, CiteScore: 1)
Intl. J. of Health Care Quality Assurance     Hybrid Journal   (Followers: 13, SJR: 0.358, CiteScore: 1)
Intl. J. of Health Governance     Hybrid Journal   (Followers: 26, SJR: 0.247, CiteScore: 1)
Intl. J. of Housing Markets and Analysis     Hybrid Journal   (Followers: 9, SJR: 0.211, CiteScore: 1)
Intl. J. of Human Rights in Healthcare     Hybrid Journal   (Followers: 6, SJR: 0.205, CiteScore: 0)
Intl. J. of Information and Learning Technology     Hybrid Journal   (Followers: 8, SJR: 0.226, CiteScore: 1)
Intl. J. of Innovation Science     Hybrid Journal   (Followers: 12, SJR: 0.197, CiteScore: 1)
Intl. J. of Intelligent Computing and Cybernetics     Hybrid Journal   (Followers: 3, SJR: 0.214, CiteScore: 1)
Intl. J. of Intelligent Unmanned Systems     Hybrid Journal   (Followers: 4)
Intl. J. of Islamic and Middle Eastern Finance and Management     Hybrid Journal   (Followers: 9, SJR: 0.375, CiteScore: 1)
Intl. J. of Law and Management     Hybrid Journal   (Followers: 2, SJR: 0.217, CiteScore: 1)
Intl. J. of Leadership in Public Services     Hybrid Journal   (Followers: 27)
Intl. J. of Lean Six Sigma     Hybrid Journal   (Followers: 8, SJR: 0.802, CiteScore: 3)
Intl. J. of Logistics Management     Hybrid Journal   (Followers: 10, SJR: 0.71, CiteScore: 2)
Intl. J. of Managerial Finance     Hybrid Journal   (Followers: 5, SJR: 0.203, CiteScore: 1)
Intl. J. of Managing Projects in Business     Hybrid Journal   (Followers: 3, SJR: 0.36, CiteScore: 2)
Intl. J. of Manpower     Hybrid Journal   (Followers: 2, SJR: 0.365, CiteScore: 1)
Intl. J. of Mentoring and Coaching in Education     Hybrid Journal   (Followers: 28, SJR: 0.426, CiteScore: 1)
Intl. J. of Migration, Health and Social Care     Hybrid Journal   (Followers: 12, SJR: 0.307, CiteScore: 1)
Intl. J. of Numerical Methods for Heat & Fluid Flow     Hybrid Journal   (Followers: 11, SJR: 0.697, CiteScore: 3)
Intl. J. of Operations & Production Management     Hybrid Journal   (Followers: 21, SJR: 2.052, CiteScore: 4)
Intl. J. of Organization Theory and Behavior     Hybrid Journal  
Intl. J. of Organizational Analysis     Hybrid Journal   (Followers: 4, SJR: 0.268, CiteScore: 1)
Intl. J. of Pervasive Computing and Communications     Hybrid Journal   (Followers: 3, SJR: 0.138, CiteScore: 1)
Intl. J. of Pharmaceutical and Healthcare Marketing     Hybrid Journal   (Followers: 4, SJR: 0.25, CiteScore: 1)
Intl. J. of Physical Distribution & Logistics Management     Hybrid Journal   (Followers: 11, SJR: 1.821, CiteScore: 4)
Intl. J. of Prisoner Health     Hybrid Journal   (Followers: 7, SJR: 0.303, CiteScore: 1)
Intl. J. of Productivity and Performance Management     Hybrid Journal   (Followers: 8, SJR: 0.578, CiteScore: 2)
Intl. J. of Public Sector Management     Hybrid Journal   (Followers: 31, SJR: 0.438, CiteScore: 1)
Intl. J. of Quality & Reliability Management     Hybrid Journal   (Followers: 8, SJR: 0.492, CiteScore: 2)
Intl. J. of Quality and Service Sciences     Hybrid Journal   (Followers: 2, SJR: 0.309, CiteScore: 1)
Intl. J. of Retail & Distribution Management     Hybrid Journal   (Followers: 6, SJR: 0.742, CiteScore: 3)
Intl. J. of Service Industry Management     Hybrid Journal   (Followers: 3)
Intl. J. of Social Economics     Hybrid Journal   (Followers: 5, SJR: 0.225, CiteScore: 1)
Intl. J. of Sociology and Social Policy     Hybrid Journal   (Followers: 54, SJR: 0.3, CiteScore: 1)
Intl. J. of Sports Marketing and Sponsorship     Hybrid Journal   (Followers: 1, SJR: 0.269, CiteScore: 1)
Intl. J. of Structural Integrity     Hybrid Journal   (Followers: 2, SJR: 0.228, CiteScore: 0)
Intl. J. of Sustainability in Higher Education     Hybrid Journal   (Followers: 14, SJR: 0.502, CiteScore: 2)
Intl. J. of Tourism Cities     Hybrid Journal   (Followers: 2, SJR: 0.502, CiteScore: 0)
Intl. J. of Web Information Systems     Hybrid Journal   (Followers: 4, SJR: 0.186, CiteScore: 1)
Intl. J. of Wine Business Research     Hybrid Journal   (Followers: 8, SJR: 0.562, CiteScore: 2)
Intl. J. of Workplace Health Management     Hybrid Journal   (Followers: 10, SJR: 0.303, CiteScore: 1)
Intl. Marketing Review     Hybrid Journal   (Followers: 15, SJR: 0.895, CiteScore: 3)
Irish J. of Occupational Therapy     Open Access   (Followers: 12)
ISRA Intl. J. of Islamic Finance     Open Access  
J. for Multicultural Education     Hybrid Journal   (Followers: 1, SJR: 0.237, CiteScore: 1)
J. of Accounting & Organizational Change     Hybrid Journal   (Followers: 6, SJR: 0.301, CiteScore: 1)
J. of Accounting in Emerging Economies     Hybrid Journal   (Followers: 9)
J. of Adult Protection, The     Hybrid Journal   (Followers: 16, SJR: 0.314, CiteScore: 1)
J. of Advances in Management Research     Hybrid Journal   (Followers: 2)
J. of Aggression, Conflict and Peace Research     Hybrid Journal   (Followers: 46, SJR: 0.222, CiteScore: 1)
J. of Agribusiness in Developing and Emerging Economies     Hybrid Journal   (SJR: 0.108, CiteScore: 0)
J. of Applied Accounting Research     Hybrid Journal   (Followers: 17, SJR: 0.227, CiteScore: 1)
J. of Applied Research in Higher Education     Hybrid Journal   (Followers: 51, SJR: 0.2, CiteScore: 0)
J. of Asia Business Studies     Hybrid Journal   (Followers: 2, SJR: 0.245, CiteScore: 1)
J. of Assistive Technologies     Hybrid Journal   (Followers: 20)
J. of Business & Industrial Marketing     Hybrid Journal   (Followers: 10, SJR: 0.652, CiteScore: 2)
J. of Business Strategy     Hybrid Journal   (Followers: 12, SJR: 0.333, CiteScore: 1)
J. of Capital Markets Studies     Open Access  
J. of Centrum Cathedra     Open Access  
J. of Children's Services     Hybrid Journal   (Followers: 5, SJR: 0.243, CiteScore: 1)
J. of Chinese Economic and Foreign Trade Studies     Hybrid Journal   (Followers: 2, SJR: 0.2, CiteScore: 0)
J. of Chinese Entrepreneurship     Hybrid Journal   (Followers: 4)
J. of Chinese Human Resource Management     Hybrid Journal   (Followers: 8, SJR: 0.173, CiteScore: 1)
J. of Communication Management     Hybrid Journal   (Followers: 6, SJR: 0.625, CiteScore: 1)
J. of Consumer Marketing     Hybrid Journal   (Followers: 20, SJR: 0.664, CiteScore: 2)
J. of Corporate Real Estate     Hybrid Journal   (Followers: 3, SJR: 0.368, CiteScore: 1)
J. of Criminal Psychology     Hybrid Journal   (Followers: 140, SJR: 0.268, CiteScore: 1)
J. of Criminological Research, Policy and Practice     Hybrid Journal   (Followers: 49, SJR: 0.254, CiteScore: 1)
J. of Cultural Heritage Management and Sustainable Development     Hybrid Journal   (Followers: 9, SJR: 0.257, CiteScore: 1)
J. of Defense Analytics and Logistics     Open Access  
J. of Documentation     Hybrid Journal   (Followers: 200, SJR: 0.613, CiteScore: 1)
J. of Economic and Administrative Sciences     Hybrid Journal   (Followers: 2)
J. of Economic Studies     Hybrid Journal   (Followers: 5, SJR: 0.733, CiteScore: 1)
J. of Economics, Finance and Administrative Science     Open Access   (Followers: 2, SJR: 0.217, CiteScore: 1)
J. of Educational Administration     Hybrid Journal   (Followers: 8, SJR: 1.252, CiteScore: 2)
J. of Enabling Technologies     Hybrid Journal   (Followers: 11, SJR: 0.369, CiteScore: 1)
J. of Engineering, Design and Technology     Hybrid Journal   (Followers: 16, SJR: 0.212, CiteScore: 1)
J. of Enterprise Information Management     Hybrid Journal   (Followers: 4, SJR: 0.827, CiteScore: 4)
J. of Enterprising Communities People and Places in the Global Economy     Hybrid Journal   (Followers: 1, SJR: 0.281, CiteScore: 1)
J. of Entrepreneurship and Public Policy     Hybrid Journal   (Followers: 8, SJR: 0.262, CiteScore: 1)
J. of European Industrial Training     Hybrid Journal   (Followers: 2)
J. of European Real Estate Research     Hybrid Journal   (Followers: 3, SJR: 0.268, CiteScore: 1)
J. of Facilities Management     Hybrid Journal   (Followers: 6, SJR: 0.33, CiteScore: 1)
J. of Family Business Management     Hybrid Journal   (Followers: 7)
J. of Fashion Marketing and Management     Hybrid Journal   (Followers: 12, SJR: 0.608, CiteScore: 2)

        1 2 | Last   [Sort by number of followers]   [Restore default list]

Similar Journals
Journal Cover
International Journal of Numerical Methods for Heat & Fluid Flow
Journal Prestige (SJR): 0.697
Citation Impact (citeScore): 3
Number of Followers: 11  
 
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 0961-5539
Published by Emerald Homepage  [356 journals]
  • Evaluation of PANS method in conjunction with non-linear eddy viscosity
           closure using OpenFOAM
    • Pages: 949 - 980
      Abstract: International Journal of Numerical Methods for Heat & Fluid Flow, Volume 29, Issue 3, Page 949-980, March 2019.
      Purpose In recent years, the partially averaged Navier–Stokes (PANS) methodology has earned acceptability as a viable scale-resolving bridging method of turbulence. To further enhance its capabilities, especially for simulating separated flows past bluff bodies, this paper aims to combine PANS with a non-linear eddy viscosity model (NLEVM). Design/methodology/approach The authors first extract a PANS closure model using the Shih’s quadratic eddy viscosity closure model [originally proposed for Reynolds-averaged Navier–Stokes (RANS) paradigm (Shih et al., 1993)]. Subsequently, they perform an extensive evaluation of the combination (PANS + NLEVM). Findings The NLEVM + PANS combination shows promising result in terms of reduction of the anisotropy tensor when the filter parameter (fk) is reduced. Further, the influence of PANS filter parameter f on the magnitude and orientation of the non-linear part of the stress tensor is closely scrutinized. Evaluation of the NLEVM + PANS combination is subsequently performed for flow past a square cylinder at Reynolds number of 22,000. The results show that for the same level of reduction in fk, the PANS + NLEVM methodology releases significantly more scales of motion and unsteadiness as compared to the traditional linear eddy viscosity model (LEVM) of Boussinesq (PANS + LEVM). The authors further demonstrate that with this enhanced ability the NLEVM + PANS combination shows much-improved predictions of almost all the mean quantities compared to those observed in simulations using LEVM + PANS. Research limitations/implications Based on these results, the authors propose the NLEVM + PANS combination as a more potent methodology for reliable prediction of highly separated flow fields. Originality/value Combination of a quadratic eddy viscosity closure model with PANS framework for simulating flow past bluff bodies.
      Citation: International Journal of Numerical Methods for Heat & Fluid Flow
      PubDate: 2019-01-08T10:27:09Z
      DOI: 10.1108/HFF-09-2018-0529
       
  • Effect of non-uniform asymmetric heating on the thermal and entropy
           generation characteristics for flow of Al2O3-water nanofluid in a
           micro-channel
    • Pages: 981 - 999
      Abstract: International Journal of Numerical Methods for Heat & Fluid Flow, Volume 29, Issue 3, Page 981-999, March 2019.
      Purpose The purpose of this study is to numerically analyze the thermal and entropy generation characteristics on two-dimensional, incompressible, laminar single-phase flow of Al2O3-water nanofluid in a micro-channel subjected to asymmetric sinusoidal wall heating with varying amplitude, length of fluctuation period and phase difference of applied heat flux for Reynolds number in the range of 25-1000. Design/methodology/approach The numerical computation is based on the Finite Element Method and the Lagrange finite element technique is used for approximating the flow variables within the computational domain. Findings The average Nusselt number increases with increasing Reynolds number (Re) for all the volume fractions of nanofluid. However, the total entropy generation decreases up to a critical value of Re and increases thereafter. Increase in volume fraction shifts the critical Re towards the lower Re regime. The average Nusselt number and total entropy generation increase with amplitude and length of fluctuation period of heat flux. The optimal choice of volume fraction for lesser entropy generation and higher heat transfer is found to be 3 per cent independent of the value of amplitude, length of fluctuation period and phase difference of the heat flux. Originality/value To the best of authors’ knowledge, the interplay of various parameters concerning non-uniform heating in achieving the maximum heat transfer with minimum irreversibility has not been investigated. Focusing on this agenda, the results of this study would benefit the industrial sector in achieving the maximum heat transfer at the cost of minimum irreversibilities with an optimal choice of inlet Reynolds number, volume fraction of nanofluid, amplitude, length of the period of fluctuation of heat flux and phase difference of applied heat flux.
      Citation: International Journal of Numerical Methods for Heat & Fluid Flow
      PubDate: 2019-01-03T02:13:29Z
      DOI: 10.1108/HFF-06-2018-0327
       
  • Numerical investigation for second law analysis of ferrofluid inside a
           porous semi annulus
    • Pages: 1079 - 1102
      Abstract: International Journal of Numerical Methods for Heat & Fluid Flow, Volume 29, Issue 3, Page 1079-1102, March 2019.
      Purpose The purpose of this paper is to present the entropy analysis of ferrofluid inside a porous space with magnetic force. Homogenous model with second law analysis is also taken into account. Design/methodology/approach Innovative model has been proposed and designed using control volume finite element method. Findings Experimental results demonstrate that Bejan number augments with augment of Rayleigh. As Hartmann number rises, exergy loss enhances. Exergy loss increases by increasing Hartmann number, whereas magnetic entropy generation reduces with the decrease of Ha. The proposed model can be used for combustion process and optimizing the performance of energy conversion system like gas turbine. Originality/value To the best of authors’ knowledge, this model is reported for the first time.
      Citation: International Journal of Numerical Methods for Heat & Fluid Flow
      PubDate: 2019-01-23T11:46:32Z
      DOI: 10.1108/HFF-10-2018-0606
       
  • Numerical simulation of annular bubble plume by vortex in cell method
    • Pages: 1103 - 1131
      Abstract: International Journal of Numerical Methods for Heat & Fluid Flow, Volume 29, Issue 3, Page 1103-1131, March 2019.
      Purpose This study aims to provide discussions of the numerical method and the bubbly flow characteristics of an annular bubble plume. Design/methodology/approach The bubbles, released from the annulus located at the bottom of the domain, rise owing to buoyant force. These released bubbles have diameters of 0.15–0.25 mm and satisfy the bubble flow rate of 4.1 mm3/s. The evolution of the three-dimensional annular bubble plume is numerically simulated using the semi-Lagrangian–Lagrangian (semi-L–L) approach. The approach is composed of a vortex-in-cell method for the liquid phase and a Lagrangian description of the gas phase. Findings First, a new phenomenon of fluid dynamics was discovered. The bubbly flow enters a transition state with the meandering motion of the bubble plume after the early stable stage. A vortex structure in the form of vortex rings is formed because of the inhomogeneous bubble distribution and the fluid-surface effects. The vortex structure of the flow deforms as three-dimensionality appears in the flow before the flow fully develops. Second, the superior abilities of the semi-L–L approach to analyze the vortex structure of the flow and supply physical details of bubble dynamics were demonstrated in this investigation. Originality/value The semi-L–L approach is applied to the simulation of the gas–liquid two-phase flows.
      Citation: International Journal of Numerical Methods for Heat & Fluid Flow
      PubDate: 2019-02-11T01:40:49Z
      DOI: 10.1108/HFF-03-2018-0094
       
  • Numerical investigation on the forced laminar convection heat transfer of
           Al2O3-water nanofluid within a three-dimensional asymmetric heated channel
           
    • Pages: 1132 - 1152
      Abstract: International Journal of Numerical Methods for Heat & Fluid Flow, Volume 29, Issue 3, Page 1132-1152, March 2019.
      Purpose The purpose of this paper is to carry out a numerical investigation to study laminar convection flow of Al2O3-water nanofluids within a three-dimensional rectangular section channel asymmetrically heated. Design/methodology/approach A three-dimensional model of the channel is designed and simulated by using Comsol Multiphysics. The finite elements method is used to perform the numerical simulation. A variety of cases are taken into account by considering Reynolds numbers ranging from 250 up to 1,000, concentration between 0 and 6 per cent, particle dimension of 20, 40 and 60 nm and inlet temperature equal to 293.15 and 320 K. A constant heat flux of 1,000 W/m2 is imposed on the top surface of the channel. Findings The results demonstrate that nanofluids guarantee improved thermal performances with respect to the base fluid, as shown by the augmented Nusselt number. On the other hand, pressure drop shows a noticeable increase; therefore, an entropy generation analysis is developed to establish optimal conditions for the system under investigation. Originality/value The originality of this work consists in the analysis of a three-dimensional asymmetric heated channel with nanofluids in laminar convection. The present work would be beneficial to improve the design of devices with particular focus on solar thermal panel.
      Citation: International Journal of Numerical Methods for Heat & Fluid Flow
      PubDate: 2019-01-23T12:03:14Z
      DOI: 10.1108/HFF-09-2018-0471
       
  • Quantification of free convection within a hemispherical annulus through a
           porous medium saturated by water-copper nanofluid
    • Pages: 1153 - 1166
      Abstract: International Journal of Numerical Methods for Heat & Fluid Flow, Volume 29, Issue 3, Page 1153-1166, March 2019.
      Purpose A porous medium saturated with a nanofluid based on pure water and copper nanoparticles is used for cooling a hemispherical electronic device contained in an annulus space. The disc of the cavity could be inclined at an angle ranging from 0 ° (horizontal disc with dome facing upwards) to 180° (horizontal disc with dome facing downwards). The important surface heat flux generated by the dome leads to high Rayleigh number values reaching 7.29 × 10^10. The purpose of this work is to examine the influence of the nanofluid saturated porous medium on the free convective heat transfer. Design/methodology/approach Heat transfer occurring between this active component and the isothermal passive cupola is quantified by means of a three-dimensional numerical study using the control volume method associated to the SIMPLE algorithm. Findings The work shows that heat transfer in the annulus space is improved by interposing a porous medium saturated with the water-copper nanofluid. Originality/value New correlation is proposed to calculate the Nusselt number for any combination of the inclination angle, the fraction volume, the Rayleigh number and the ratio between the thermal conductivities of the porous medium and the fluid. The wide ranges corresponding to these parameters allow the thermal design of this electronic equipment for various configurations.
      Citation: International Journal of Numerical Methods for Heat & Fluid Flow
      PubDate: 2019-02-07T03:09:23Z
      DOI: 10.1108/HFF-09-2018-0467
       
  • Effects of wave breaking on the oceanic boundary layer in hurricane
           conditions
    • Pages: 1167 - 1177
      Abstract: International Journal of Numerical Methods for Heat & Fluid Flow, Volume 29, Issue 3, Page 1167-1177, March 2019.
      Purpose Wave breaking significantly affects the exchange process between ocean and atmosphere. This paper aims to simulate the upper ocean dynamics under the influence of wave breaking, which may help to figure out the transport of energy by these breakers. Design/methodology/approach The authors use a breaker-LES model to simulate the oceanic boundary layer in hurricane conditions, in which breakers become the main source of momentum and energy instead of traditional wind stress. Findings The mean horizontal velocities and energy increase rapidly with wind speed, reflecting that input from atmosphere dominates the coherent structure in the upper ocean. The penetration ability of a breaker limits its effective depth and thus the total turbulent kinetic energy (TKE) decreases sharply near the surface. Langmuir circulation is the main source of TKE in deeper water. The authors compared the dissipation rate (e) in the simulations with two estimates and found that the model tends to the scaling of ε∼z–3.4 at extreme wind speeds. Originality/value The probability distribution of breakers is also discussed based on the balance between the input from atmosphere and output by wave breaking. The authors considered the contribution of micro-scale breakers and revaluated the probability density function. The results show stability in hurricane conditions.
      Citation: International Journal of Numerical Methods for Heat & Fluid Flow
      PubDate: 2019-02-18T02:32:21Z
      DOI: 10.1108/HFF-09-2018-0508
       
  • Computation of flow and heat transfer through channels with periodic
           dimple/protrusion walls using low-Reynolds number turbulence models
    • Pages: 1178 - 1207
      Abstract: International Journal of Numerical Methods for Heat & Fluid Flow, Volume 29, Issue 3, Page 1178-1207, March 2019.
      Purpose This paper aims to predict turbulent flow and heat transfer through different channels with periodic dimple/protrusion walls. More specifically, the performance of various low-Re k-ε turbulence models in prediction of local heat transfer coefficient is evaluated. Design/methodology/approach Three low-Re number k-ε turbulence models (the zonal k-ε, the linear k-ε and the nonlinear k-ε) are used. Computations are performed for three geometries, namely, a channel with a single dimpled wall, a channel with double dimpled walls and a channel with a single dimple/protrusion wall. The predictions are obtained using an in house finite volume code. Findings The numerical predictions indicate that the nonlinear k-ε model predicts a larger recirculation bubble inside the dimple with stronger impingement and upwash flow than the zonal and linear k-ε models. The heat transfer results show that the zonal k-ε model returns weak thermal predictions in all test cases in comparison to other turbulence models. Use of the linear k-ε model leads to improvement in heat transfer predictions inside the dimples and their back rim. However, the most accurate thermal predictions are obtained via the nonlinear k-ε model. As expected, the replacement of the algebraic length-scale correction term with the differential version improves the heat transfer predictions of both linear and nonlinear k-ε models. Originality/value The most reliable turbulence model of the current study (i.e. nonlinear k-ε model) may be used for design and optimization of various thermal systems using dimples for heat transfer enhancement (e.g. heat exchangers and internal cooling system of gas turbine blades).
      Citation: International Journal of Numerical Methods for Heat & Fluid Flow
      PubDate: 2019-02-11T01:39:49Z
      DOI: 10.1108/HFF-09-2018-0469
       
  • Influence of duct parameters on the acoustic wave generation
    • Abstract: International Journal of Numerical Methods for Heat & Fluid Flow, Ahead of Print.
      Purpose This paper aims to determine the influence of geometrical features of the channel on the acoustic wave generation in a ducted cavity. The analysis is focussed on the effects of the change in the entrance length upstream the cavity and the height. The study is supposed to investigate boundary layer and acoustic wave parameters, and an attempt will be made to determine the correlation between the geometrical dimension and those parameters. Design/methodology/approach Analysis is conducted with the aim of a computational fluid dynamics (CFD) tool and selected results are validated with experimental investigations. The influence of grid resolution and time discretization is analysed. Four different entrance lengths and height are investigated. Qualitative and quantitative comparison between cases is presented. Findings The investigations prove the small influence of the entrance length on acoustic wave generation, but channel height due to wave reflection and interference inside of the cavity has a significant impact on wave frequency and sound pressure level. Channel height has also impact on generation and shape of the vortex created in the cavity inlet. Originality/value The paper extends the knowledge of phenomena taking place in the ducted cavities. Results obtained from these investigations will be useful in designing new cooling techniques and in noise reduction. The CFD analysis makes it possible to determine the correlations between channel dimensions and SPL function and frequency of sound waves.
      Citation: International Journal of Numerical Methods for Heat & Fluid Flow
      PubDate: 2019-05-21T07:47:19Z
      DOI: 10.1108/HFF-10-2018-0611
       
  • Development of hybrid method for coupled conduction-radiation heat
           transfer in two-dimensional irregular enclosure considering
           thermo-radiative effects and varying thermal conductivity
    • Abstract: International Journal of Numerical Methods for Heat & Fluid Flow, Ahead of Print.
      Purpose This study aims to perform a comprehensive investigation to model the thermal characteristics of a coupled conduction-radiation heat transfer in a two-dimensional irregular enclosure including a triangular-shaped heat source. Design/methodology/approach For this purpose, a promising hybrid technique based on the concepts of blocked-off method, FVM and DOM is developed. The enclosure consists of several horizontal, vertical and oblique walls, and thermal conductivity within the enclosure varies directly with temperature and indirectly with position. To simplify the complex geometry, a promising mathematical model is introduced using blocked-off method. Emitting, absorbing and non-isotropic scattering gray are assumed as the main radiative characteristics of the steady medium. Findings DOM and FVM are, respectively, applied for solving radiative transfer equation (RTE) and the energy equation, which includes conduction, radiation and heat source terms. The temperature and heat flux distributions are calculated inside the enclosure. For validation, results are compared with previous data reported in the literature under the same conditions. Results and comparisons show that this approach is highly efficient and reliable for complex geometries with coupled conduction-radiation heat transfer. Finally, the effects of thermo-radiative parameters including surface emissivity, extinction coefficient, scattering albedo, asymmetry factor and conduction-radiation parameter on temperature and heat flux distributions are studied. Originality/value In this paper, a hybrid numerical method is used to analyze coupled conduction-radiation heat transfer in an irregular geometry. Varying thermal conductivity is included in this analysis. By applying the method, results obtained for temperature and heat flux distributions are presented and also validated by the data provided by several previous papers.
      Citation: International Journal of Numerical Methods for Heat & Fluid Flow
      PubDate: 2019-05-14T12:44:06Z
      DOI: 10.1108/HFF-11-2018-0667
       
  • Determination of heat transfer coefficient in a T-shaped cavity by means
           of solving the inverse heat conduction problem
    • Abstract: International Journal of Numerical Methods for Heat & Fluid Flow, Ahead of Print.
      Purpose T-shaped cavities occur by design in many technical applications. An example of such a stator cavity is the side space between the guide vane carriers and the outer casing of a steam turbine. Thermal conditions inside it have a significant impact on the deformation of the turbine casing. In order to improve its prediction, the purpose of this paper is to provide a methodology to gain better knowledge of the local heat transfer at the cavity boundaries based on experimental results. Design/methodology/approach To determine the heat transfer coefficient distribution inside a model cavity with the help of a scaled generic test rig, an inverse heat conduction problem is posed and a method for solving such type of problems in the form of linear combinations of Trefftz functions is presented. Findings The results of the calculations are compared with another inverse method using first-order gradient optimization technique as well as with estimated values obtained with an analytic two-dimensional thermal network model, and they show an excellent agreement. The calculation procedure is proved to be numerically stable for different degrees of complexity of the sought boundary conditions. Originality/value This paper provides a universal and robust methodology for the fast direct determination of an arbitrary distribution of heat transfer coefficients based on material temperature measurements spread over the confining wall.
      Citation: International Journal of Numerical Methods for Heat & Fluid Flow
      PubDate: 2019-05-13T02:08:40Z
      DOI: 10.1108/HFF-09-2018-0484
       
  • Effect of partially wet-surface condition on the performance of fin-tube
           heat exchanger
    • Abstract: International Journal of Numerical Methods for Heat & Fluid Flow, Ahead of Print.
      Purpose This study aims to investigate heat and mass transfer in a one-row heat exchanger. The required equations are obtained based on two-dimensional model analysis in a cell of the heat exchanger. By using finite difference approach, the obtained equations are solved to determine distribution of temperature and the efficiency of the heat exchanger in the case of partially wet surface. In this research, Lewis Number as unity and water vapor saturation as parabolic are assumed. Obtained results show that increase in thermal conductivity fin leads to decreasing thermal resistance; therefore, temperature changes in radial from center to out of fin are reduced and efficiency of fin increases. Design/methodology/approach In this regard, fin material plays a significant role in fin efficiency. Changes in airflow also result in an efficiency increase by temperature and relative humidity, and efficiency is decreased by airflow velocity increase, and these changes are almost linear. Moreover, the fins with more wet surface are more sensitive to changes in fin dimensions and air flow characteristics, and it is a result of conjugate heat transfer mechanism, in which latent heat transfer in the fins with more wet surface has a significant role. Findings Thermal property and geometry of the fin under wet conditions play a more important role than the fin under dry conditions. Changes in airflow result in an efficiency increase by temperature and relative humidity, and efficiency is decreased by airflow velocity increase, and these changes are almost linear. Fins with more wet surface are more sensitive to changes in fin dimensions and air flow characteristics. Originality/value Effects of the temperature of water supply and mass flow rate were considered in the study. The results had good agreement with actual data.
      Citation: International Journal of Numerical Methods for Heat & Fluid Flow
      PubDate: 2019-05-13T02:03:00Z
      DOI: 10.1108/HFF-07-2018-0362
       
  • Numerical study and POD snapshot analysis of flow characteristics for
           pulsating turbulent opposing jets
    • Abstract: International Journal of Numerical Methods for Heat & Fluid Flow, Ahead of Print.
      Purpose The purpose of this study is to investigate the coherent structures of pulsed opposing jets by large eddy simulation (LES) model and proper orthogonal decomposition (POD) snapshot method. Flow pulsation as an active flow control method is considered for the enhancement of transport phenomena in impinging jets. The effect of flow pulsation parameters such as pulsation signal shape and frequency on the vortical coherent structures, the energy content of primary modes and their variation are studied numerically. Design/methodology/approach In this study, flow field of turbulent pulsating opposing jets has been simulated using LES. The result of the simulation in different time steps (snapshots) are stored and POD is applied on the snapshots. In this study, the POD method and calculation of spatial modes has been done using OpenFOAM, and time coefficients have been calculated using a MATLAB code. Findings The results of this study show that the flow excitation has a great effect on the coherent structure formation and the energy containment of fundamental modes of the flow. When the flow was excited by a harmonic sinusoidal or step function, the turbulent kinetic energy accumulated in the set of primary modes. On the other hand, the pulsed opposing jets had more regularity compared to the steady jets. The shapes, patterns and energy values of dominant modes depended on the inlet pulsation signal. An increase in pulsation frequency leads to an augmentation in energy content of the primary modes. Research limitations/implications The predictions may be extended to include various pulsation conditions such as: various amplitudes, Reynolds number and aspect ratio. Practical implications The results of this study are a valuable source of information for active control of transport phenomena in opposing jet configurations which is used in different industrial applications such as cooling, combustion, reactors, heating and drying processes. Originality/value In this study, the coherent structures and energy content of primary modes was studied for the first time by LES model and POD snapshot method and a comprehensive discussion on numerical results is provided.
      Citation: International Journal of Numerical Methods for Heat & Fluid Flow
      PubDate: 2019-05-03T02:21:59Z
      DOI: 10.1108/HFF-07-2018-0382
       
  • An adaptive inner iterative pressure-based algorithm for steady and
           unsteady incompressible flows
    • Abstract: International Journal of Numerical Methods for Heat & Fluid Flow, Ahead of Print.
      Purpose Pressure-based methods have been demonstrated to be powerful for solving many practical problems in engineering. In many pressure-based methods, inner iterative processes are proposed to get efficient solutions. However, the number of inner iterations is set empirically and kept fixed during the whole computation for different problems, which is overestimated in some computations but underestimated in other computations. This paper aims to develop an algorithm with adaptive inner iteration processes for steady and unsteady incompressible flows. Design/methodology/approach In this work, with the use of two different criteria in two inner iterative processes, a mechanism is proposed to control inner iteration processes to make the number of inner iterations vary during computing according to different problems. By doing so, adaptive inner iteration processes can be achieved. Findings The adaptive inner iterative algorithm is verified to be valid by solving classic steady and unsteady incompressible problems. Results show that the adaptive inner iteration algorithm works more efficient than the fixed inner iteration one. Originality/value The algorithm with adaptive inner iteration processes is first proposed in this paper. As the mechanism for controlling inner iteration processes is based on physical meaning and the feature of iterative calculations, it can be used in any methods where there exist inner iteration processes. It is not limited for incompressible flows. The performance of the adaptive inner iteration processes in compressible flows is conducted in a further study.
      Citation: International Journal of Numerical Methods for Heat & Fluid Flow
      PubDate: 2019-05-03T02:16:38Z
      DOI: 10.1108/HFF-09-2018-0483
       
  • Physical aspects of Darcy-Forchheimer bidirectional flow in carbon
           nanotubes (SWCNTs and MWCNTs)
    • Abstract: International Journal of Numerical Methods for Heat & Fluid Flow, Ahead of Print.
      Purpose This paper aims to examine the three-dimensional (3D) flow of carbon nanotubes (CNTs) due to bidirectional nonlinearly stretching surface by considering porous medium. Characteristics of both single-walled CNTs and multi-walled CNTs are discussed by considering Xue model. Darcy–Forchheimer model is used for flow saturating porous medium. Design/methodology/approach Optimal homotopy analysis method is used for the development of series solutions. Findings The authors deal with 3D Darcy–Forchheimer flow of CNTs over a nonlinearly stretching surface. Heat transport mechanism is discussed in the presence of Xue model. The homogeneous and heterogeneous effects are also accounted. The mathematical modeling is computed using boundary-layer approximations. Originality/value No such work has been done yet in the literature.
      Citation: International Journal of Numerical Methods for Heat & Fluid Flow
      PubDate: 2019-05-03T02:12:37Z
      DOI: 10.1108/HFF-12-2018-0770
       
  • Entropy generation in radiative flow of Ree-Eyring fluid due to due
           rotating disks
    • Abstract: International Journal of Numerical Methods for Heat & Fluid Flow, Ahead of Print.
      Purpose This study aims to examine the flow characteristics of Ree–Eyring fluid between two rotating disks. The characteristics of heat transfer are discussed in presence of viscous dissipation, heat source/sink and nonlinear radiative heat flux. Design/methodology/approach Nonlinear flow expressions lead to ordinary ones through adequate similarity transformations. The ordinary differential system has been tackled through optimal homotopic method. The impact of different flow variables on the velocity field, entropy generation rate and temperature fields is graphically discussed. The surface drag force and heat transfer rate are numerically examined via various pertinent parameters. Findings By minimization of values of stretching parameter and Brinkman number, the entropy generation rate can be controlled. The entropy generation rate enhances for higher values of magnetic parameter, while the Bejan number is decreased via magnetic parameter. Originality/value No such work is yet published in the literature.
      Citation: International Journal of Numerical Methods for Heat & Fluid Flow
      PubDate: 2019-05-03T02:09:02Z
      DOI: 10.1108/HFF-11-2018-0642
       
  • Effect of replacing nanofluid instead of water on heat transfer in a
           channel with extended surfaces under a magnetic field
    • Abstract: International Journal of Numerical Methods for Heat & Fluid Flow, Ahead of Print.
      Purpose The purpose of this study is to conduct a numerical analysis of flow and heat transfer of water–aluminum oxide nanofluid in a channel with extended surfaces in the presence of a constant magnetic field. The channel consists of two parallel plates and five obstacles of constant temperature on the lower wall of the channel. The upper wall and the inlet and outlet lengths of the lower wall are insulated. A uniform magnetic field of the magnitude B0 is located beneath the obstacles. The nanofluid enters the channel with a uniform velocity and temperature, and a fully developed flow leaves the channel. Design/methodology/approach The control volume-based finite difference and the SIMPLE algorithm were used for numerical solution. In addition to examining the effect of the Reynolds number, the effects of Hartman number, the volume fraction of nanoparticles, the height of obstacles, the length of obstacles and the distance between the obstacles were investigated. Findings According to the results, the heat transfer rate increases with an increasing Reynolds number. As the Hartmann number increases, the heat transfer rate increases. The heat transfer rate also increases with an increase in the volume fraction of nanoparticles. The mean Nusselt number is reduced by an increasing height of obstacles. An increase in the distance between the obstacles in the presence of a magnetic field does not have a significant impact on the heat transfer rate. However, the heat transfer rate increases in the absence of a magnetic field, as the distance between the obstacles increases. Originality/value This paper is original and unpublished and is not being considered for publication elsewhere.
      Citation: International Journal of Numerical Methods for Heat & Fluid Flow
      PubDate: 2019-05-03T02:03:06Z
      DOI: 10.1108/HFF-06-2018-0277
       
  • Energy saving with using of elliptic pillows in turbulent flow of
           two-phase water-silver nanofluid in a spiral heat exchanger
    • Abstract: International Journal of Numerical Methods for Heat & Fluid Flow, Ahead of Print.
      Purpose Increasing heat transfer rate in spiral heat exchangers is possible by using conventional methods such as increasing number of fluid passes and counter flowing. In addition, newer ideas such as using pillows as baffles in the path of cold and hot fluids and using nanofluids can increase heat transfer rate. The purpose of this study is to simulate turbulent flow and heat transfer of two-phase water-silver nanofluid with 0-6 Vol.% nanoparticle concentration in a 180° path of spiral heat exchanger with elliptic pillows. Design/methodology/approach In this simulation, the finite volume method and two-phase mixture model are used. The walls are subjected to constant heat flux of q″ = 150,000 Wm−2. The inlet fluid enters curves path of spiral heat exchanger with uniform temperature Tin = 300 K. After flowing past the pillows and traversing the curved route, the working fluid exchanges heat with hot walls and then exits from the section. In this study, the effect of radiation is disregarded because of low temperature range. Also, temperature jump and velocity slipping are disregarded. The effects of thermophoresis and turbulent diffusion on nanofluid heat transfer are disregarded. By using finite volume method and two-phase mixture model, simulations are performed. Findings The results show that the flow and heat transfer characteristics are dependent on the height of pillows, nanoparticle concentration and Reynolds number. Increasing Reynolds number, nanoparticle concentration and pillow height causes an increase in Nusselt number, pressure drop and pumping power. Originality/value Turbulent flow and heat transfer of two-phase water-silver nanofluid of 0-6 per cent volume fraction in a 180° path of spiral heat exchanger with elliptic pillows is simulated.
      Citation: International Journal of Numerical Methods for Heat & Fluid Flow
      PubDate: 2019-04-17T08:52:53Z
      DOI: 10.1108/HFF-10-2018-0594
       
  • Exploration of flow and heat transfer of non-Newtonian nanofluid over a
           stretching sheet by considering slip factor
    • Abstract: International Journal of Numerical Methods for Heat & Fluid Flow, Ahead of Print.
      Purpose Here, the present paper characteristics flow and heat transfer of non-Newtonian nanofluid over a stretching sheet. Energy expression is modeled subject to slip factor phenomenon. Consideration of chemical reaction characterizes the mass transfer mechanism. Design/methodology/approach The use of transformation variables reduces the PDEs into non-linear ODEs. The obtained nonlinear complex problems are computed numerically through RKF-45 technique. The effects of the different physical parameters on the temperature and concentration distribution are analyzed. Findings The nature of the reduced Nusselt number, reduced Sherwood number and skin friction coefficient also described as a function of different parameters arising in the problem. It is found that the rate of mass transfer enhances for enhancing values Brownian motion parameter and thermophoresis parameter. Originality/value The nature of the reduced Nusselt number, reduced Sherwood number and skin friction coefficient also described as a function of different parameters arising in the problem. It is found that, the rate of mass transfer enhances for enhancing values Brownian motion parameter and thermophoresis parameter.
      Citation: International Journal of Numerical Methods for Heat & Fluid Flow
      PubDate: 2019-04-17T08:46:54Z
      DOI: 10.1108/HFF-11-2018-0687
       
  • Computational fluid dynamics and laminar heat transfer of water/Cu
           nanofluid in ribbed microchannel with a two-phase approach
    • Abstract: International Journal of Numerical Methods for Heat & Fluid Flow, Ahead of Print.
      Purpose This study aims to numerically investigate the heat transfer and laminar forced and two-phase flow of Water/Cu nanofluid in a rectangular microchannel with oblique ribs with angle of attacks equal to 0-45°. This simulation was conducted in the range of Reynolds numbers of 5-120 in volume fractions of 0, 2 and 4 per cent of solid nanoparticles in three-dimensional space. Design/methodology/approach This study investigates the effect of the changes of angle of attack of rectangular rib on heat transfer and hydrodynamics of two-phase flow. This study was done in three-dimensional space and simulation was done with finite volume method. SIMPLEC algorithm and second-order discretization of equations were used to increase the accuracy of results. The usage of nanofluid, application of rips with different angles of attacks and using the two-phase mixture method is the distinction of this paper compared with other studies. Findings The results of this research revealed that the changing angle of attack of ribs is an effective factor in heat transfer enhancement. On the other hand, the existence of rib on the internal surfaces of a microchannel increases friction coefficient. By increasing the volume fraction of nanoparticles, due to the augmentation of fluid density and viscosity, the pressure drop increases significantly. For all of the angle of attacks studied in this paper, the maximum rate of performance evaluation criterion has been obtained in Reynolds number of 30 and the minimum amount of performance evaluation criterion was been obtained in Reynolds numbers of 5 and 120. Originality/value Many studies have been done in the field of heat transfer in ribbed microchannel. In this paper, the laminar flow in the ribbed microchannel Water/Cu nanofluid in a rectangular microchannel by using two-phase mixture method is numerically investigated with different volume fractions (0-4 per cent), Reynolds numbers (5-120) and angle of attacks of rectangular rib in the indented microchannel (0-45°).
      Citation: International Journal of Numerical Methods for Heat & Fluid Flow
      PubDate: 2019-04-10T01:55:06Z
      DOI: 10.1108/HFF-05-2018-0243
       
  • Simulations of flame propagation during the ignition process in an annular
           multiple-injector combustor
    • Abstract: International Journal of Numerical Methods for Heat & Fluid Flow, Ahead of Print.
      Purpose Ignition process is a critical issue in combustion systems. It is particularly important for reliability and safety prospects of aero-engine. This paper aims to numerically investigate the burner-to-burner propagation during ignition process in a full annular multiple-injector combustor and then validate it by comparing with experimental results. Design/methodology/approach The annular multiple-injector experimental setup features 16 swirling injectors and two quartz tubes providing optical accesses to high-speed imaging of flames. A Reynolds averaged Navier–Stokes model, adaptive mesh refinement (AMR) and complete San Diego chemistry are used to predict the ignition process. Findings The ignition process shows an overall agreement with experiment. The integrated heat release rate of simulation and the integrated light intensity of experiment is also within reasonable agreement. The flow structure and flame propagation dynamics are carefully analyzed. It is found that the flame fronts propagate symmetrically at an early stage and asymmetrically near merging stage. The flame speed slows down before flame merging. Overall, the numerical results show that the present numerical model can reliably predict the flame propagation during the ignition process. Originality/value The dedicated AMR method together with detailed chemistry is used for predicting the unsteady ignition procedure in a laboratory-scale annular combustor for the first time. The validation shows satisfying agreements with the experimental investigations. Some details of flow structures are revealed to explain the characteristics of unsteady flame propagations.
      Citation: International Journal of Numerical Methods for Heat & Fluid Flow
      PubDate: 2019-04-09T10:14:33Z
      DOI: 10.1108/HFF-08-2018-0432
       
  • Natural convection of a hybrid nanofluid subjected to non-uniform magnetic
           field within porous medium including circular heater
    • Abstract: International Journal of Numerical Methods for Heat & Fluid Flow, Ahead of Print.
      Purpose This paper aims to numerically investigate the natural convection heat transfer of a hybrid nanofluid into a porous cavity exposed to a variable magnetic field. Design/methodology/approach The non-linear elliptical governing equations have been solved numerically using control volume based finite element method. The effects of different governing parameters including Rayleigh number (Ra = 103 − 106), Hartman number (Ha = 0 − 50), volume fraction of nanoparticles (φ = 0 − 0.02), curvature of horizontal isolated wall (a = 0.85 − 1.15), porosity coefficient (ε = 0.1 − 0.9) and Darcy number (Da = 10−5 − 10−1) have been studied. Findings The results indicate that at low Darcy numbers close to 0, the average Nusselt number Nua enhances as porosity coefficient increases. For a = 1 and a = 1.15 in comparison with a = 0.85, the stretching of the isothermal lines is maintained from the left side to the right side and vice versa, which indicates increased natural convection heat transfer for this configuration of the top and bottom walls. In addition, at higher Rayleigh numbers, by increasing the Hartmann number, a significant decrease is observed in the Nusselt number, which can be attributed to the decreased power of the flow. Originality/value The authors believe that all the results, both numerical and asymptotic, are original and have not been published elsewhere.
      Citation: International Journal of Numerical Methods for Heat & Fluid Flow
      PubDate: 2019-04-09T10:12:13Z
      DOI: 10.1108/HFF-08-2018-0428
       
  • Effect of nanofluids on heat transfer and cooling system of the
           photovoltaic/thermal performance
    • Abstract: International Journal of Numerical Methods for Heat & Fluid Flow, Ahead of Print.
      Purpose Effective cooling is one of the challenges for photovoltaic thermal (PVT) systems to maintain the PV operating temperature. One of the best ways to enhance rate of heat transfer of the PVT system is using advanced working fluids such as nanofluids. The purpose of this research is to develop a numerical model for designing different form of thermal collector systems with different materials. It is concluded that PVT system operated by nanofluid is more effective than water-based PVT system. Design/methodology/approach In this research, a three-dimensional numerical model of PVT with new baffle-based thermal collector system has been developed and solved using finite element method-based COMSOL Multyphysics software. Water-based different nanofluids (Ag, Cu, Al, etc.), various solid volume fractions up to 3 per cent and variation of inlet temperature (20-40°C) have been applied to obtain high thermal efficiency of this system. Findings The numerical results show that increasing solid volume fraction increases the thermal performance of PVT system operated by nanofluids, and optimum solid concentration is 2 per cent. The thermal efficiency is enhanced approximately by 7.49, 7.08 and 4.97 per cent for PVT system operated by water/Ag, water/Cu and water/Al nanofluids, respectively, compared to water. The extracted thermal energy from the PVT system decreases by 53.13, 52.69, 42.37 and 38.99 W for water, water/Al, water/Cu and water/Ag nanofluids, respectively, due to each 1°C increase in inlet temperature. The heat transfer rate from heat exchanger to cooling fluid enhances by about 18.43, 27.45 and 31.37 per cent for the PVT system operated by water/Al, water/Cu, water/Ag, respectively, compared to water. Originality/value This study is original and is not being considered for publication elsewhere. This is also not currently under review with any other journal.
      Citation: International Journal of Numerical Methods for Heat & Fluid Flow
      PubDate: 2019-04-09T10:10:12Z
      DOI: 10.1108/HFF-04-2018-0174
       
  • MHD mixed convection of nanofluid in a cubic cavity with a conductive
           partition for various nanoparticle shapes
    • Abstract: International Journal of Numerical Methods for Heat & Fluid Flow, Ahead of Print.
      Purpose This paper aims to numerically examine the mixed convection of SiO2-water nanofluid flow in a three-dimensional (3D) cubic cavity with a conductive partition considering various shapes of the particles (spherical, cylindrical, blade, brick). The purpose is to analyze the effects of various pertinent parameters such as Richardson number (between 0.1 and 10), Hartmann number (between 0 and 10), solid nanoparticle volume fraction (between 0 and 0.04), particle shape (spherical, cylindrical, blade, brick) and different heights and lengths of the conductive partition on the fluid flow and heat transfer characteristics. Design/methodology/approach The numerical simulation was performed by using Galerkin-weighted residual finite element method for various values of Richardson number, Hartmann number, solid nanoparticle volume fraction, particle shape (spherical, cylindrical, blade, brick) and different heights and lengths of the conductive partition. Two models for the average Nusselt number were proposed for nanofluids with spherical and cylindrical particle by using multi-layer feed-forward neural networks. Findings It was observed that the average Nusselt number reduces for higher values of Richardson number and Hartmann number, while enhances for higher values of nanoparticle volume fraction. Among various types of particle shapes, blade ones perform the worst and cylindrical ones perform the best in terms of heat transfer enhancement, but this is not significant which is less than 3 per cent. The average Nusselt number deteriorates by about 6.53per cent for nanofluid at the highest volume fraction of spherical particle shapes, but it is 11.75per cent for the base fluid when Hartmann number is increased from 0 to 10. Conductive partition geometrical parameters (length and height) do not contribute to much to heat transfer process for the 3D cavity, except for the case when height of the partition reaches 0.8 times the height of the cubic cavity, the average Nusselt number value reduces by about 25per cent both for base fluid and for nanofluid when compared to case with cavity height which is 0.2 times the height of the cubic cavity. Originality/value Based on the literature survey, a 3D configuration for MHD mixed convection of nanofluid flow in a cavity with a conductive partition considering the effects of various particle shapes has never been studied in the literature. This study is a first attempt to use a conductive partition with nanofluid of various particle shapes to affect the fluid flow and heat transfer characteristics in a 3D cubic cavity under the influence of magnetic field. Partial or all findings of this study could be used for the design and optimization of realistic 3D thermal configurations that are encountered in practice and some of the applications were already mentioned above. In this study, thermal performance of the system was obtained in terms of average heat transfer coefficient along the hot surface, and it is modeled with multi-layer feed-forward neural networks.
      Citation: International Journal of Numerical Methods for Heat & Fluid Flow
      PubDate: 2019-04-09T10:08:50Z
      DOI: 10.1108/HFF-04-2018-0176
       
  • Natural convection of non-Newtonian nanofluid flow between two vertical
           parallel plates
    • Abstract: International Journal of Numerical Methods for Heat & Fluid Flow, Ahead of Print.
      Purpose The purpose of this paper is to carry out a detailed investigation to study the natural convection of a non-Newtonian nanofluid flow between two vertical parallel plates. In this study, sodium alginate has been taken as a base fluid and nanoparticles that added to it are copper and silver. Maxwell–Garnetts and Brinkman models are used to calculate the effective thermal conductivity and viscosity of nanofluid, respectively. Design/methodology/approach The authors used two methods in this study, namely, Galerkin’s method and homotopy perturbation method. Findings This paper investigates the velocity and temperature profile of nanofluid and the real fluid flow between two vertical parallel plates. The impacts of physical parameters such as nanofluid volume fraction and dimensionless non-Newtonian viscosity are discussed. Originality/value Coupled non-linear differential equations are solved for velocity and temperature. A model is proposed in such a way that the authors may get the solution of real fluid from the nanofluid by neglecting the nano term. The authors do not require a further calculation for real fluid problem.
      Citation: International Journal of Numerical Methods for Heat & Fluid Flow
      PubDate: 2019-04-09T10:06:50Z
      DOI: 10.1108/HFF-06-2018-0302
       
  • SLAC – a semi-Lagrangian artificial compressibility solver for
           steady-state incompressible flows
    • Abstract: International Journal of Numerical Methods for Heat & Fluid Flow, Ahead of Print.
      Purpose The purpose of this paper is the development of a new density-based (DB) semi-Lagrangian method to speed up the conventional pressure-based (PB) semi-Lagrangian methods. Design/methodology/approach The semi-Lagrangian-based solvers are typically PB, i.e. semi-Lagrangian pressure-based (SLPB) solvers, where a Poisson equation is solved for obtaining the pressure field and ensuring a divergence-free flow field. As an elliptic-type equation, the Poisson equation often relies on an iterative solution, so it can create a challenge of parallel computing and a bottleneck of computing speed. This study proposes a new DB semi-Lagrangian method, i.e. the semi-Lagrangian artificial compressibility (SLAC), which replaces the Poisson equation by a hyperbolic continuity equation with an added artificial compressibility (AC) term, so a time-marching solution is possible. Without the Poisson equation, the proposed SLAC solver is faster, particularly for the cases with more computational cells, and better suited for parallel computing. Findings The study compares the accuracy and the computing speeds of both SLPB and SLAC solvers for the lid-driven cavity flow and the step-flow problems. It shows that the proposed SLAC solver is able to achieve the same results as the SLPB, whereas with a 3.03 times speed up before using the OpenMP parallelization and a 3.35 times speed up for the large grid number case (512 × 512) after the parallelization. The speed up can be improved further for larger cases because of increasing the condition number of the coefficient matrixes of the Poisson equation. Originality/value This paper proposes a method of avoiding solving the Poisson equation, a typical computing bottleneck for semi-Lagrangian-based fluid solvers by converting the conventional PB solver (SLPB) to the DB solver (SLAC) through the addition of the AC term. The method simplifies and facilitates the parallelization process of semi-Lagrangian-based fluid solvers for modern HPC infrastructures, such as OpenMP and GPU computing.
      Citation: International Journal of Numerical Methods for Heat & Fluid Flow
      PubDate: 2019-04-09T10:04:51Z
      DOI: 10.1108/HFF-05-2018-0181
       
  • Numerical investigations on particle separation in dynamic separators
    • Abstract: International Journal of Numerical Methods for Heat & Fluid Flow, Ahead of Print.
      Purpose Dynamic separator is an equipment having a rotor and static vanes and is used to separate solids from gas-solids flow based on size. Particle separation in a dynamic separator happens due to complex interchanges between multiple forces exerted in the separation zone. Currently, there is only limited knowledge concerning the working principles of separation. This paper aims to systematically study a dynamic separator using numerical models to get insights into particle separation. Design/methodology/approach The Lagrangian–Eulerian formulation is used to simulate gas-solid flow. Multiple frames of reference using stage interpolation are used to account for rotation. Periodic symmetry in the equipment is exploited to create a simplified numerical model. The predictions from the numerical model are compared against available experimental data. Findings The numerical results indicate that only when particle collision is included, the separation efficiency trend from the experiment is matched by numerical predictions. Further, it is shown that at the same range of rotor speeds where numerical results predict increased separation efficiency, the solid pressure due to particle collision also reaches its maximum value. The gas flow and particle behavior in the separator are explained in detail. Originality/value The importance of particle collision in separation is interesting because traditionally, particle separation is assumed to be influenced by three forces, namely, centrifugal force, drag force and gravity. The numerical results, however, point to the contribution by particle collision, in addition to the above three forces.
      Citation: International Journal of Numerical Methods for Heat & Fluid Flow
      PubDate: 2019-04-03T11:44:02Z
      DOI: 10.1108/HFF-10-2018-0567
       
  • Electromagnetic field analysis and cooling system design for high power
           switched reluctance motor
    • Abstract: International Journal of Numerical Methods for Heat & Fluid Flow, Ahead of Print.
      Purpose The electromagnetic field and cooling system of a high power switched reluctance motor (SRM) are studied numerically. The geometry of the motor and its main components are established using a computer-aided design software in the actual size. This study aims to evaluate the resulting thermal losses using the electromagnetic analysis of the motor. Design/methodology/approach In the electromagnetic analysis, the Joule’s loss in the copper wires of the coil windings and the iron losses (the eddy currents loss and the hysteresis loss) are considered. The flow and heat transfer model for the thermal analysis of the motor including the conduction in solid parts and convection in the fluid part is introduced. The magnetic losses are imported into the thermal analysis model in the form of internal heat generation in motor components. Several cooling system approaches were introduced, such as natural convection cooling, natural convection cooling with various types of fins over the motor casing, forced conviction air-cooled cooling system using a mounted fan, casing surface with and without heat sinks, liquid-cooled cooling system using the water in a channel shell and a hybrid air-cooled and liquid-cooled cooling system. Findings The results of the electromagnetics analysis show that the low rotational speed of the motor induces higher currents in coil windings, which in turn, it causes higher copper losses in SRM coil windings. For higher rotational speed of SRM, the core loss is higher than the copper loss is in SRM due to the higher frequency. An air-cooled cooling system is used for cooling of SRM. The results reveal when the rotational speed is at 4,000 rpm, the coil loss would be at the maximum value. Therefore, the coil temperature is about 197.9°C, which is higher than the tolerated standard temperature insulation material. Hence, the air-cooled system cannot reduce the temperature to the safe temperature limitation of the motor and guarantee the safe operation of SRM. Thus, a hybrid system of both air-cooled and liquid-cooled cooling system with mounting fins at the outer surface of the casing is proposed. The hybrid system with the liquid flow of Re = 1,500 provides a cooling power capable of safe operation of the motor at 117.2°C, which is adequate for standard insulation material grade E. Originality/value The electromagnetic field and cooling system of a high power SRM in the presence of a mounted fan at the rear of the motor are analyzed. The thermal analysis is performed for both of the air-cooled and liquid-cooled cooling systems to meet the cooling demands of the motor for the first time.
      Citation: International Journal of Numerical Methods for Heat & Fluid Flow
      PubDate: 2019-03-14T09:31:29Z
      DOI: 10.1108/HFF-08-2018-0450
       
  • Modeling of combustion and hydrodynamics for a coal-fired supercritical
           boiler with double-reheat cycle
    • Abstract: International Journal of Numerical Methods for Heat & Fluid Flow, Ahead of Print.
      Purpose The design and retrofit of the heat exchangers in a boiler should take into account the processes occurring on the side of combustion and steam. For this reason, this study aims to couple a one-dimensional hydrodynamic model of steam with computational fluid dynamics (CFD) simulation of flue gas. Design/methodology/approach Radiant/semi-radiant platen heat exchangers are simplified as plane surfaces for CFD, while convective heat exchangers are introduced into the CFD simulation as energy/momentum absorption sources. Findings Numerical simulation is performed for a 1,000 MWe coal-fired ultra-supercritical boiler. The calculation results are validated by the thermodynamic design data. Tube outside surface temperature, as well as ash deposit temperature distributions, are obtained. Originality/value Complex tube arrangements can be completed with the aid of AutoCAD, and therefore, the simulation could offer detailed information of heat exchangers. In a word, a more reliable modeling of the whole steam generation process is achieved.
      Citation: International Journal of Numerical Methods for Heat & Fluid Flow
      PubDate: 2019-02-25T10:14:59Z
      DOI: 10.1108/HFF-08-2018-0456
       
  • MHD mixed convection of nanofluid in a three-dimensional vented cavity
           with surface corrugation and inner rotating cylinder
    • Abstract: International Journal of Numerical Methods for Heat & Fluid Flow, Ahead of Print.
      Purpose This study aims to numerically examine mixed convection of CuO-water nanofluid in a three-dimensional (3D) vented cavity with inlet and outlet ports under the influence of an inner rotating circular cylinder, homogeneous magnetic field and surface corrugation effects. In practical applications, it is possible to encounter some of the considered configurations in a vented cavity such as magnetic field, rotating cylinder and it is also possible to specially add some of the active and passive control means to control the convection inside the cavity such as adding nanoparticles, corrugating the surfaces. The complicated physics with nanofluid under the effects of magnetic field and inclusion of complex 3D geometry make it possible to use the results of this numerical investigation for the design, control and optimization of many thermal engineering systems as mentioned above. Design/methodology/approach The bottom surface is corrugated with a rectangular wave shape, and the rotating cylinder surface and cavity bottom surface were kept at constant hot temperatures while the cold fluid enters the inlet port with uniform velocity. The complicated interaction between the forced convection and buoyancy-driven convection coupled with corrugated and rotating surfaces in 3D configuration with magnetic field, which covers a wide range of thermal engineering applications, are numerically simulated with finite element method. Effects of various pertinent parameters such as Richardson number (between 0.01 and 100), Hartmann number (between 0 and 1,000), angular rotational speed of the cylinder (between −30 and 30), solid nanoparticle volume fraction (between 0 and 0.04), corrugation height (between 0 and 0.18H) and number (between 1 and 20) on the convective heat transfer performance are numerically analyzed. Findings It was observed that the magnetic field suppresses the recirculation zone obtained in the lower part of the inlet port and enhances the average heat transfer rate, which is 10.77 per cent for water and 6.86 per cent for nanofluid at the highest strength. Due to the thermal and electrical conductivity enhancement of nanofluid, there is 5 per cent discrepancy in the Nusselt number augmentation with the nanoadditive inclusion in the absence and presence of magnetic field. The average heat transfer rate of the corrugated surface enhances by about 9.5 per cent for counter-clockwise rotation at angular rotational speed of 30 rad/s as compared to motionless cylinder case. Convective heat transfer characteristics are influenced by introducing the corrugation waves. As compared to number of waves, the height of the corrugation has a slight effect on the heat transfer variation. When the number of rectangular waves increases from N = 1 to N = 20, approximately 59 per cent of the average heat transfer reduction is achieved. Originality/value In this study, mixed convection of CuO-water nanofluid in a 3D vented cavity with inlet and outlet ports is numerically examined under the influence of an inner rotating circular cylinder, homogeneous magnetic field and surface corrugation effects. To the best of authors knowledge such a study has never been performed. In practical applications, it is possible to encounter some of the considered configurations in a vented cavity such as magnetic field, rotating cylinder and it is also possible to specially add some of the active and passive control means to control the convection inside the cavity such as adding nanoparticles, corrugating the surfaces. The complicated physics with nanofluid under the effects of magnetic field and inclusion of complex 3D geometry make it possible to use the results of this numerical investigation for the design, control and optimization of many thermal engineering systems as mentioned above.
      Citation: International Journal of Numerical Methods for Heat & Fluid Flow
      PubDate: 2019-02-20T03:39:43Z
      DOI: 10.1108/HFF-10-2018-0566
       
  • Instabilities of SWCNT conveying laminar, incompressible and viscous fluid
           flow
    • Abstract: International Journal of Numerical Methods for Heat & Fluid Flow, Ahead of Print.
      Purpose This study aims to study the transverse vibration and instabilities of the fluid-conveying single-walled carbon nanotubes (CNTs). To this purpose, the Euler–Bernoulli beam model is used. Also, the surface effects, small-size effects of the both fluid and structure and two different elastic mediums viscoelastic and Pasternak elastic are investigated. Design/methodology/approach To consider the nano-scale for the CNT, the strain-inertia gradient theory is used and to solve the governing equation of motion for the system, the Galerkin’s method is used. The effect of the flow velocity, aspect ratio, characteristic lengths of the mentioned theory, effects of Knudsen number and effects of the Winkler, the Pasternak elastic and the viscoelastic medium on the frequencies and stabilities of the system are studied. The effects of the above parameters on the vibrational behavior are investigated both separately and simultaneously. Findings The results show that the critical flow velocity value is increased as the aspect ratio, characteristic lengths, Winkler modulus, shear and damping factors increase. Also, the critical flow velocity is increased by considering the surface effects. In addition, the consequence of increase in the nano-flow-size effects (Knudsen number) is decreasing the critical flow velocity. Moreover, it can be observed that the effect of the shear factor on increasing the critical flow velocity is different from the rest of parameters. Originality/value Use of Timoshenko and modified couple stress theories and taking into account Von-Karman expressions for investigating the nonlinear vibrations of triple-walled CNTs buried within Pasternak foundation.
      Citation: International Journal of Numerical Methods for Heat & Fluid Flow
      PubDate: 2019-02-11T01:41:49Z
      DOI: 10.1108/HFF-10-2018-0563
       
  • Numerical investigation of nonlinear vibration analysis for triple-walled
           carbon nanotubes conveying viscous fluid
    • Abstract: International Journal of Numerical Methods for Heat & Fluid Flow, Ahead of Print.
      Purpose The purpose of this paper is to investigate nonlinear vibrations of triple-walled carbon nanotubes buried within Pasternak foundation carrying viscous fluids. Design/methodology/approach Considering the geometry of nanotubes, the governing equations were initially derived using Timoshenko and modified couple stress theories and by taking into account Von-Karman expressions. Then, by determining boundary conditions, type of fluid motion, Knudsen number and, ultimately, fluid viscosity, the principal equation was solved using differential quadrature method, and linear and nonlinear nanotube frequencies were calculated. Findings The results indicated that natural frequency is decreased as the fluid velocity and aspect ratio increase. Moreover, as the aspect ratio is increased, the results converge for simple and fixed support boundary conditions, and the ratio of nonlinear to linear frequencies approaches. Natural frequency of vibrations and critical velocity increase as Pasternak coefficient and characteristic length increase. As indicated by the results, by assuming a non-uniform velocity for the fluid and a slip boundary condition at Kn = 0.05, reductions of 10.714 and 28.714% were observed in the critical velocity, respectively. Moreover, the ratio of nonlinear to linear base frequencies decreases as the Winkler and Pasternak coefficients, maximum deflection of the first wall and characteristic length are increased in couple stress theory. Originality/value This paper is a numerical investigation of nonlinear vibration analysis for triple-walled carbon nanotubes conveying viscous fluid.
      Citation: International Journal of Numerical Methods for Heat & Fluid Flow
      PubDate: 2019-02-07T11:58:48Z
      DOI: 10.1108/HFF-10-2018-0600
       
  • Two-phase investigation of water-Al2O3 nanofluid in a micro concentric
           annulus under non-uniform heat flux boundary conditions
    • Abstract: International Journal of Numerical Methods for Heat & Fluid Flow, Ahead of Print.
      Purpose This is a 3D numerical study of convective heat transfer through a micro concentric annulus governing non-uniform heat flux boundary conditions employing water-Al2O3 nanofluid. The nanofluid is modeled using two-phase mixture model, as it has a good agreement to experimental results. Design/methodology/approach Half of the inner pipe surface area of the annulus section of a double pipe heat exchanger is exposed to a constant heat flux which two models are considered to divide the exposing surface area to smaller ones considering the fact that in all cases half of the inner pipe surface area has to be exposed to the heat flux: in model (A), the exposing surface area is divided radially to two parts (A1), four parts (A2) and eight parts (A3) by covering the whole length of the annulus and in model (B) the exposing surface area is divided axially to two parts (B1), four parts (B2) and eight parts (B3) by covering half of the annulus radially. Findings The results reveal that model (B) leads to higher Nusselt numbers compared to model (A); however, at Reynolds number 10, model (A3) exceeds model (B3). The average Nusselt number is increased up to 142 and 83 per cent at models (A3) with Reynolds number 10 and model (B3) with Reynolds number 1000, respectively. Originality/value This paper is a two-phase investigation of water-Al2O3 nanofluid in a micro concentric annulus under non-uniform heat flux boundary conditions.
      Citation: International Journal of Numerical Methods for Heat & Fluid Flow
      PubDate: 2019-01-25T12:57:26Z
      DOI: 10.1108/HFF-11-2018-0628
       
  • Role of magnetic field on forced convection of nanofluid in a branching
           channel
    • Abstract: International Journal of Numerical Methods for Heat & Fluid Flow, Ahead of Print.
      Purpose Numerical study of nanofluid forced convection within a branching channel was performed under the influence of a uniform magnetic field. The purpose of this study is to enhance the heat transfer performance of the separated flow at the branching channel with the use of magnetic field and nanofluid. The use of magnetic field and enhancement in both the thermal conductivity and electrical conductivity with the inclusion of the nanoparticles provides favorable thermophysical properties of the nanofluid when it used as a heat transfer fluid in a branching channel. The results of this study may be used to control the thermal performance in a branching channel and further optimization studies in the presence of magnetic field. Design/methodology/approach Galerkin weighted residual finite element method was used for the simulations. The numerical simulation results are performed by changing the inclination angle of the lower branching channel (between 0° and 90°), thermophysical properties of the fluid via inclusion of nanoparticles (between 0 and 0.04), Reynolds number (between 100 and 400) and magnetic field strength (Hartmann number changes between 0 and 15). Findings It was observed that the recirculation zones and reattachment length of the upper and lower branching channels are affected by the variation of those parameters. Reattachment lengths increase with the augmentation of the Reynolds number and deterioration of the Hartmann number. Average Nusselt number becomes higher for higher values of Hartmann number and solid particle volume fraction. Inclusion of the nanoparticle to the base fluid is very effective for the configuration with higher values of Hartmann number. An optimum value of the inclination angle of the lower branching channel is observed, beyond which heat transfer rate is significantly reduced due to the establishment of a large vortex in the upper branching channel and restriction of the fluid motion. Originality/value In this study, forced convection of nanofluid flow in a branching channel under the effect of magnetic field was numerically studied. Magnetic field effects with nanoparticle inclusion to the base fluid on the convective heat transfer was analyzed for various inclination angles of the lower branching channel. Flow separation at the junction of the channels and thus convective heat transfer rate are influenced by the variation of these parameters. There are many studies related to application of the magnetic field with nanofluids, and a few of them are related to configurations with separated flows. To the best of the authors’ knowledge, there exist no studies for the application of nanofluids and magnetic field for the convective heat transfer in a branching channel. This topic is of importance as there are many engineering applications of the branching channels.
      Citation: International Journal of Numerical Methods for Heat & Fluid Flow
      PubDate: 2019-01-25T01:01:06Z
      DOI: 10.1108/HFF-10-2018-0568
       
  • Modified algebraic model of laminar-turbulent transition for internal
           flows
    • Abstract: International Journal of Numerical Methods for Heat & Fluid Flow, Ahead of Print.
      Purpose For internal flows with small values of the Reynolds number, there is often at a considerable distance from the pipe inlet cross-section a change of the flow form from laminar to turbulent. To describe this phenomenon of laminar-turbulent transition in the pipe, also parallel-plate channel flow, a modified algebraic intermittency model was used. The original model for bypass transition developed by S. Kubacki and E. Dick was designed for simulating bypass transition in turbomachinery. Design/methodology/approach A modification of mentioned model was proposed. Modified model is suitable for simulating internal flows in pipes and parallel-plate channels. Implementation of the modified model was made using the OpenFOAM framework. Values of several constants of the original model were modified. Findings For selected Reynolds numbers and turbulence intensities (Tu), localization of laminar breakdown and fully turbulent flow was presented. Results obtained in this work were compared with corresponding experimental results available in the literature. It is particularly worth noting that asymptotic values of wall shear stress in flow channels and asymptotic values of axis velocity obtained during simulations are similar to related experimental and theoretical results. Originality/value The modified model allows precision numerical simulation in the area of transitional flow between laminar, intermittent and turbulent flows in pipes and parallel-plate channels. Proposed modified algebraic intermittency model presented in this work is described by a set of two additional partial differential equations corresponding with k-omega turbulence model presented by Wilcox (Wilcox, 2006).
      Citation: International Journal of Numerical Methods for Heat & Fluid Flow
      PubDate: 2019-01-23T11:42:56Z
      DOI: 10.1108/HFF-10-2018-0597
       
  • Model structure effect on static aeroelastic deformation of the NASA CRM
    • Abstract: International Journal of Numerical Methods for Heat & Fluid Flow, Ahead of Print.
      Purpose This paper aims to present a computational aeroelastic capability based on a fluid–structure interaction (FSI) methodology and validate it using the NASA Common Research Model (CRM). Focus is placed on the effect of the wind tunnel model structural features on the static aeroelastic deformations. Design/methodology/approach The FSI methodology couples high-fidelity computational fluid dynamics to a simplified beam representation of the finite element model. Beam models of the detailed CRM wind tunnel model and a simplified CRM model are generated. The correlation between the numerical simulations and wind tunnel data for varying angles of attack is analysed and the influence of the model structure on the static aeroelastic deformation and aerodynamics is studied. Findings The FSI results follow closely the general trend of the experimental data, showing the importance of considering structural model deformations in the aerodynamic simulations. A thorough examination of the results reveals that it is not unequivocal that the fine details of the structural model are important in the aeroelastic predictions. Research limitations/implications The influence of some changes in structural deformation on transonic wing aerodynamics appears to be complex and non-linear in nature and should be subject to further investigations. Originality/value It is shown that the use of a beam model in the FSI approach provides a reliable alternative to the more costly coupling with the full FE model. It also highlights the non-necessity to develop precise, detailed structural models for accurate FSI simulations.
      Citation: International Journal of Numerical Methods for Heat & Fluid Flow
      PubDate: 2019-01-18T02:43:18Z
      DOI: 10.1108/HFF-07-2018-0352
       
  • Performance assessment of novel photovoltaic thermal system using
           nanoparticle in phase change material
    • Abstract: International Journal of Numerical Methods for Heat & Fluid Flow, Ahead of Print.
      Purpose Nanotechnology has developed gradually in recent years and it is encountered in various applications. It has many usage area especially in energy systems. The purpose of this study, in a photovoltaic thermal system, thermal behaviours of a PV panel has been investigated by energy and exergy analysis method using a phase change material inserted 5 per cent weighted Al2O3 nanoparticle. Design/methodology/approach In this study, one of the three different PV panels was kept normally, the other one was filled with a phase changing material (paraffin-wax) and the last panel was filled with the mixture of a nanoparticle and paraffin-wax. Findings After the analyses, especially during the time intervals when the radiation is high, it is found that the panel with Np-paraffin mixture has a high electrical and thermal efficiency. In addition, as a result of the exergy analyses, average exergy efficiency of the panel with Np-paraffin mixture has been determined as 10 per cent, whereas that of the panel with paraffin as 9.2 per cent. Originality/value Nanoparticles had not been used with PCMs in photovoltaic–thermal systems in the studies made before.
      Citation: International Journal of Numerical Methods for Heat & Fluid Flow
      PubDate: 2019-01-18T02:27:38Z
      DOI: 10.1108/HFF-05-2018-0257
       
  • Choke flutter instability sources tracking with linearized calculations
    • Abstract: International Journal of Numerical Methods for Heat & Fluid Flow, Ahead of Print.
      Purpose The choke flutter is a fluid-structure interaction that can lead to the failure of fan or compressor blade in turbojet engines. In ultra high bypass ratio (UHBR) fans, the choke flutter appears at part-speed regimes and at low or negative incidence when a strong shock-wave chokes the blade to blade channel. The purpose of this study is to locate the main excitation sources and improving the understanding of the different work exchange mechanisms. This work contributes to avoiding deficient and dangerous fan design. Design/methodology/approach In this paper, an UHBR fan is analyzed using a time-linearized Reynolds-averaged Navier–Stokes equation solver to investigate the choke flutter. The steady-state and the imposed vibration (inter blade phase angle, reduced frequency and mode shape) are selected to be in choke flutter situation. Superposition principle induced by the linearization allow to decompose the blade in numerous small subsections to track the contribution of each local vibration to the global damping. All simulations have been performed on a two-dimensional blade to blade extraction. Findings Result analysis points to a restricted number of excitation sources at the trailing edge which induce a large part of the work exchange in a limited region of the airfoil. Main phenomena suspected are the shock-wave motion and the shock-wave/boundary layer interaction. Originality/value An original excitation source tracking methodology allowed by the linearized calculation is addressed and applied to a UHBR fan test case.
      Citation: International Journal of Numerical Methods for Heat & Fluid Flow
      PubDate: 2019-01-16T03:02:20Z
      DOI: 10.1108/HFF-06-2018-0281
       
  • Entropy generation analysis of magneto-nanoliquids embedded with aluminium
           and titanium alloy nanoparticles in microchannel with partial slips and
           convective conditions
    • Abstract: International Journal of Numerical Methods for Heat & Fluid Flow, Ahead of Print.
      Purpose Outstanding features such as superior electrical conductivity and thermal conductivity of alloy nanoparticles with working fluids make them ideal materials to be used as coolants in microelectromechanical systems (MEMSs). This paper aims to investigate the effects of different alloy nanoparticles such as AA7075 and Ti6Al4V on microchannel flow of magneto-nanoliquids with partial slip and convective boundary conditions. Flow features are explored with the effects of magnetism and nanoparticle shape. Heat transport of fluid includes radiative heat, internal heat source/sink, viscous and Joule heating phenomena. Design/methodology/approach Suitable dimensionless variables are used to reduce dimensional governing equations into dimensionless ordinary differential equations. The relevant dimensionless ordinary differential systems are computed numerically by using Runge–Kutta–Fehlberg-based shooting approach. Pertinent results of velocity, temperature, entropy number and Bejan number for assorted values of physical parameters are comprehensively discussed. Also, a closed-form solution is obtained for momentum equation for a particular case. Analytical results agree perfectly with numerical results. Findings It is established that the entropy production can be improved with radiative heat, Joule heating, convective heating and viscous dissipation aspects. The entropy production is higher in the case of Ti6Al4V-H2O nanofluid than AA7075-H2O. Further, the inequality Ns(ξ)Sphere> Ns(ξ)Hexahedran> Ns(ξ)Tetrahydran> Ns(ξ)Column> Ns(ξ)Lamina holds true. Originality/value Effects of aluminium and titanium alloy nanoparticles in microchannel flows by using viscous dissipation and Joule heating are investigated for the first time. Flow features are explored with the effects of magnetism and nanoparticle shape. The results for different alloy nanoparticles such as AA7075 and Ti6Al4V have been compared.
      Citation: International Journal of Numerical Methods for Heat & Fluid Flow
      PubDate: 2019-01-07T09:56:31Z
      DOI: 10.1108/HFF-06-2018-0301
       
  • Numerical investigation on turbulent convective heat transfer of nanofluid
           flow in a square cross-sectioned duct
    • Abstract: International Journal of Numerical Methods for Heat & Fluid Flow, Ahead of Print.
      Purpose The purpose of this study is to numerically investigate the heat transfer enhancement by using two different nanofluids flow throughout the square duct under a constant heat flux (500 × 103 W/m2). Design/methodology/approach In numerical computations, ANSYS Fluent code based on the finite volume method was used to solve governing equations by iteratively. Water, Al2O3-water and TiO2-water nanofluids were used for different flow velocities changing 1 m/s to 8 m/s (i.e. Reynolds number varying from 3,000 to 100,000). Findings The results were compared with results published previously in the literature and close agreement was observed especially considering Dittus and Boelter correlation for water. It was found that from the obtained results, increasing flow velocity and volume fractions of nanoparticles has caused to increase Nu number for all cases. Besides, variations of pressure drop, Darcy friction factor are presented graphically and discussed in detail. The results are consistent with a deviation of 1.3 to 15 per cent with the results of other researchers. Originality/value The effects of the Re numbers and volume fractions of nanoparticles (0.01 ≤ Φ ≤ 0.04) on the heat transfer and fluid flow characteristics such as average Nu number, pressure drop (ΔP) and Darcy friction factor (f) were investigated.
      Citation: International Journal of Numerical Methods for Heat & Fluid Flow
      PubDate: 2019-01-04T12:06:29Z
      DOI: 10.1108/HFF-06-2018-0260
       
  • Optimal distribution of metal foam inserts in a double-pipe heat exchanger
    • Abstract: International Journal of Numerical Methods for Heat & Fluid Flow, Ahead of Print.
      Purpose In the present research, a numerical investigation is carried out to study the fluid flow and heat transfer in a double-pipe, counter-flow heat exchanger exploiting metal foam inserts partially in both pipes. The purpose of this study is to achieve the optimal distribution of a fixed volume of metal foam throughout the pipes which provides the maximum heat transfer rate with the minimum pressure drop increase. Design/methodology/approach The governing equations are solved using the finite volume method. The metal foams are divided into different number of parts and positioned at different locations. The number of metal foam parts, their placements and their volume ratios in each pipe are sought to reach the optimal conditions. The four-piece metal foam with optimized placement and partitioning volume ratios is selected as the best layout. The effects of the permeability of metal foam on the Nusselt number, the performance evaluation criteria (PEC) and the overall heat transfer coefficient are investigated. Findings It was observed that the heat transfer rate, the overall heat transfer coefficient and the effectiveness of the heat exchanger can be improved as high as 69, 124 and 9 per cent, respectively, while the highest value of PEC is 1.36. Practical implications Porous materials are widely used in thermo-fluid systems such as regenerators, heat sinks, solar collectors and heat exchangers. Originality/value Having less pressure drop than fully filled heat exchangers, partially filled heat exchangers with partitioned metal foams distributed optimally enhance heat transfer rate more economically.
      Citation: International Journal of Numerical Methods for Heat & Fluid Flow
      PubDate: 2019-01-04T11:28:40Z
      DOI: 10.1108/HFF-04-2018-0162
       
  • A comprehensive review on natural convection flow and heat transfer
    • Pages: 834 - 877
      Abstract: International Journal of Numerical Methods for Heat & Fluid Flow, Volume 29, Issue 3, Page 834-877, March 2019.
      Purpose The purpose of this paper is to carry out a comprehensive review of some latest studies devoted to natural convection phenomenon in the enclosures because of its significant industrial applications. Design/methodology/approach Geometries of the enclosures have considerable influences on the heat transfer which will be important in energy consumption. The most useful geometries in engineering fields are treated in this literature, and their effects on the fluid flow and heat transfer are presented. Findings A great variety of geometries included with different physical and thermal boundary conditions, heat sources and fluid/nanofluid media are analyzed. Moreover, the results of different types of methods including experimental, analytical and numerical are obtained. Different natures of natural convection phenomenon including laminar, steady-state and transient, turbulent are covered. Overall, the present review enhances the insight of researchers into choosing the best geometry for thermal process. Originality/value A comprehensive review on the most practical geometries in the industrial application is performed.
      Citation: International Journal of Numerical Methods for Heat & Fluid Flow
      PubDate: 2018-12-04T02:30:42Z
      DOI: 10.1108/HFF-06-2018-0272
       
  • Stability analysis, solition solutions and Gaussian solitons of the
           generalized nonlinear Schrödinger equation with higher order terms
    • Pages: 878 - 889
      Abstract: International Journal of Numerical Methods for Heat & Fluid Flow, Volume 29, Issue 3, Page 878-889, March 2019.
      Purpose The purpose of this paper is to study stability analysis, solition solutions and Gaussian solitons of the generalized nonlinear Schrödinger equation with higher order terms, which can be used to describe the propagation properties of optical soliton solutions. Design/methodology/approach The authors apply the ansatz method and the Hamiltonian system technique to find its bright, dark and Gaussian wave solitons and analyze its modulation instability analysis and stability analysis solution. Findings The results imply that the generalized nonlinear Schrödinger equation has bright, dark and Gaussian wave solitons. Meanwhile, the authors provide the graphical analysis of such solutions to better understand their dynamical behavior. Some constraint conditions are provided which can guarantee the existence of solitons. The authors analyze its modulation instability analysis and stability analysis solution. Originality/value These results may help us to further study the local structure and the interaction of solutions in generalized nonlinear Schrödinger -type equations. The authors hope that the results provided in this work can help enrich the dynamic behavior of the generalized nonlinear Schrödinger--type equations.
      Citation: International Journal of Numerical Methods for Heat & Fluid Flow
      PubDate: 2018-12-19T03:04:06Z
      DOI: 10.1108/HFF-08-2018-0448
       
  • Numerical investigation on the improved three-hole cooling unit with the
           trench
    • Pages: 890 - 914
      Abstract: International Journal of Numerical Methods for Heat & Fluid Flow, Volume 29, Issue 3, Page 890-914, March 2019.
      Purpose This study aims to introduce a three-hole cooling unit to improve downstream cooling performance by jet interaction and coalescence at a lower manufacture cost. Design/methodology/approach A new three-hole cooling unit is proposed. Reynolds-averaged Navier–Stokes (RANS) simulation is performed in the present study. The CFD package ANSYS CFX is used to predict film-cooling effectiveness and flow fields. Findings The results show that, at pitch ratio P/D = 3, Case 4 configuration with a round hole upstream and two trenched holes downstream can obtain a high cooling performance at a lower manufacture cost, especially at the higher turbulence. Considering the effect of increased pitch ratio, Case 6 configurations of three staggered trenched holes show a superior downstream cooling performance than Case 4 configurations. Case 6 configurations have the potential of achieving a high cooling performance with a reduced number of holes and less coolant flow. Research limitations/implications The application of these cooling units in the turbine passage will be conducted in the future. The more detailed flow field will be simulated by large eddy simulation in the following research. Practical implications The round and trenched cooling holes have been proved to be achievable in the manufacture. This combined three-hole cooling unit will give the opportunity to increase turbine inlet temperature further. Originality/value Both cooling performance and practical manufacture are taken into account. This cooling scheme will give a superior surface protection on the hot components.
      Citation: International Journal of Numerical Methods for Heat & Fluid Flow
      PubDate: 2018-12-04T02:30:50Z
      DOI: 10.1108/HFF-06-2018-0344
       
  • Free convection heat transfer and entropy generation analysis of
           water-Fe3O4/CNT hybrid nanofluid in a concentric annulus
    • Pages: 915 - 934
      Abstract: International Journal of Numerical Methods for Heat & Fluid Flow, Volume 29, Issue 3, Page 915-934, March 2019.
      Purpose This paper aims to numerically investigate the heat transfer and entropy generation characteristics of water-based hybrid nanofluid in natural convection flow inside a concentric horizontal annulus. Design/methodology/approach The hybrid nanofluid is prepared by suspending tetramethylammonium hydroxide-coated Fe3O4 (magnetite) nanoparticles and gum arabic (GA)-coated carbon nanotubes (CNTs) in water. The effects of nanoparticle volume concentration and Rayleigh number on the streamlines, isotherms, average Nusselt number and the thermal, frictional and total entropy generation rates are investigated comprehensively. Findings Results show the advantageous effect of hybrid nanofluid on the average Nusselt number. Furthermore, the study of entropy generation shows the increment of both frictional and thermal entropy generation rates by increasing Fe3O4 and CNT concentrations at various Rayleigh numbers. Increasing Rayleigh number from 103 to 105, at Fe3O4 concentration of 0.9 per cent and CNT concentration of 1.35 per cent, increases the average Nusselt number, thermal entropy generation rate and frictional entropy generation rate by 224.95, 224.65 and 155.25 per cent, respectively. Moreover, increasing the Fe3O4 concentration from 0.5 to 0.9 per cent, at Rayleigh number of 105 and CNT concentration of 1.35 per cent, intensifies the average Nusselt number, thermal entropy generation rate and frictional entropy generation rate by 18.36, 22.78 and 72.7 per cent, respectively. Originality/value To the best knowledge of the authors, there are not any archival publications considering the detailed behaviour of the natural convective heat transfer and entropy generation of hybrid nanofluid in a concentric annulus.
      Citation: International Journal of Numerical Methods for Heat & Fluid Flow
      PubDate: 2018-11-30T02:14:06Z
      DOI: 10.1108/HFF-08-2018-0424
       
  • Three-dimensional rotating Darcy–Forchheimer flow with activation
           energy
    • Pages: 935 - 948
      Abstract: International Journal of Numerical Methods for Heat & Fluid Flow, Volume 29, Issue 3, Page 935-948, March 2019.
      Purpose The purpose of this study is to study flow caused by rotating frame. Effects of Darcy–Forchheimer and porous medium are considered to study velocity field. Concentration field is discussed in presence of activation energy. Darcy–Forchheimer in a rotating frame is examined. Flow because of stretched sheet fills the porous space. Binary chemical reaction is entertained. Resulting system is numerically solved. The plots are arranged for rotational parameter, porosity parameter, coefficients of inertia, Prandtl number and Schmidt number. It is revealed that rotation on velocity has opposite effects when compared with temperature and concentration distributions. Skin friction coefficients and local Nusselt and Sherwood numbers are numerically discussed. Design/methodology/approach Darcy–Forchheimer in a rotating frame is examined. Flow because of stretched sheet fills the porous space. Binary chemical reaction is entertained. Resulting system is numerically solved. The plots are arranged for rotational parameter, porosity parameter, coefficients of inertia, Prandtl number and Schmidt number. It is revealed that rotation on velocity has opposite effects when compared with temperature and concentration distributions. Skin friction coefficients and local Nusselt and Sherwood numbers are numerically discussed. Findings The major findings here are as follows: an addition in porosity λ causes decay in velocity f′(η) while there is opposite behavior for temperature θ(η) and concentration ϕ(η) fields. θ and ϕ via β have similar results qualitatively. There is an opposite behavior of Pr on temperature and concentration. Inverse behavior of λ on ϕ and wall mass flux is noted. Concentration ϕ is decreasing function of reaction rate constant σ. Skin friction coefficient has similar qualitative results for λ and β. Temperature gradient −θ′(0) is decreased by λ and β. Originality/value Here, the authors are interested to investigate rotating flow in a porous space. Dissipation and radiation effects are neglected. Effects of activation energy are studied. This work is not done yet in literature.
      Citation: International Journal of Numerical Methods for Heat & Fluid Flow
      PubDate: 2018-12-13T11:06:30Z
      DOI: 10.1108/HFF-06-2018-0292
       
  • Homoclinic breather-wave and singular periodic wave for a
           (2 + 1)D GSWW equation
    • Pages: 1000 - 1009
      Abstract: International Journal of Numerical Methods for Heat & Fluid Flow, Volume 29, Issue 3, Page 1000-1009, March 2019.
      Purpose The purpose of this paper is to discuss the homoclinic breathe-wave solutions and the singular periodic solutions for (2 + 1)-dimensional generalized shallow water wave (GSWW) equation. Design/methodology/approach The Hirota bilinear method, the Lie symmetry method and the non-Lie symmetry method are applied to the (2 + 1)D GSWW equation. Findings A reduced (1 + 1)D potential KdV equation can be derived, and its soliton solutions are also presented. Research limitations/implications As a typical nonlinear evolution equation, some dynamical behaviors are also discussed. Originality/value These results are very useful for investigating some localized geometry structures of dynamical behaviors and enriching dynamical features of solutions for the higher dimensional systems.
      Citation: International Journal of Numerical Methods for Heat & Fluid Flow
      PubDate: 2018-12-04T02:33:31Z
      DOI: 10.1108/HFF-08-2018-0436
       
  • Numerical modeling of Glauert type exponentially decaying wall jet flows
           of nanofluids using Tiwari and Das’ nanofluid model
    • Pages: 1010 - 1038
      Abstract: International Journal of Numerical Methods for Heat & Fluid Flow, Volume 29, Issue 3, Page 1010-1038, March 2019.
      Purpose The purpose of this study is to present a simple analytic solution to wall jet flow of nanofluids. The concept of exponentially decaying wall jet flows proposed by Glauert (1956) is considered. Design/methodology/approach A proper similarity variables are used to transform the system of partial differential equations into a system of ordinary (similarity) differential equations. This system is then solved analytically. Findings Dual solutions are found and a stability analysis has been done. These solutions show that the first solution is physically realizable, whereas the second solution is not practicable. Originality/value The present results are original and new for the study of fluid flow and heat transfer over a static permeable wall, as they successfully extend the problem considered by Glauert (1956) to the case of nanofluids.
      Citation: International Journal of Numerical Methods for Heat & Fluid Flow
      PubDate: 2018-12-19T03:00:06Z
      DOI: 10.1108/HFF-08-2018-0437
       
  • Stagnation-point flow and heat transfer of upper-convected Oldroyd-B MHD
           nanofluid with Cattaneo–Christov double-diffusion model
    • Pages: 1039 - 1057
      Abstract: International Journal of Numerical Methods for Heat & Fluid Flow, Volume 29, Issue 3, Page 1039-1057, March 2019.
      Purpose The purpose of this paper is to investigate the two-dimensional stagnation-point flow, heat and mass transfer of an incompressible upper-convected Oldroyd-B MHD nanofluid over a stretching surface with convective heat transfer boundary condition in the presence of thermal radiation, Brownian motion, thermophoresis and chemical reaction. The process of heat and mass transfer based on Cattaneo–Christov double-diffusion model is studied, which can characterize the features of thermal and concentration relaxations factors. Design/methodology/approach The governing equations are developed and similarly transformed into a set of ordinary differential equations, which are solved by a newly approximate analytical method combining the double-parameter transformation expansion method with the base function method (DPTEM-BF). Findings An interesting phenomenon can be found that all the velocity profiles first enhance up to a maximal value and then gradually drop to the value of the stagnation parameter, which indicates the viscoelastic memory characteristic of Oldroyd-B fluid. Moreover, it is revealed that the thickness of the thermal and mass boundary layer is increasing with larger values of thermal and concentration relaxation parameters, which indicates that Cattaneo–Christov double-diffusion model restricts the heat and mass transfer comparing with classical Fourier’s law and Fick’s law. Originality/value This paper focuses on stagnation-point flow, heat and mass transfer combining the constitutive relation of upper-convected Oldroyd-B fluid and Cattaneo–Christov double diffusion model.
      Citation: International Journal of Numerical Methods for Heat & Fluid Flow
      PubDate: 2018-12-12T08:37:49Z
      DOI: 10.1108/HFF-06-2018-0295
       
  • Lattice Boltzmann simulation of free convection’s hydrothermal aspects
           in a finned/multi-pipe cavity filled with CuO-water nanofluid
    • Pages: 1058 - 1078
      Abstract: International Journal of Numerical Methods for Heat & Fluid Flow, Volume 29, Issue 3, Page 1058-1078, March 2019.
      Purpose This paper aims to investigate the natural convection fluid flow and heat transfer in a finned/multi-pipe cavity. Design/methodology/approach The cavity is filled with the CuO-water nanofluid. The Koo–Kleinstreuer–Li model is used to estimate the dynamic viscosity and consider Brownian motion. On the other hand, the effect of the shapes of nanoparticles on the thermal conductivity and related heat transfer rate is presented. Findings In the present investigation, the governing parameters are Rayleigh number, CuO nanoparticle concentration in pure water and the thermal arrangements of internal active fins and solid bodies. Impacts of these parameters on the nanofluid flow, heat transfer rate, total/local entropy generation and heatlines are presented. It is concluded that adding nanoparticles to the pure fluid has a significant positive influence on the heat transfer performance. In addition, the average Nusselt number and total entropy generation have direct a relationship with the Rayleigh number. The thermal arrangement of the internal bodies and fins is a good controlling tool to determine the desired magnitude of heat transfer rate. Originality/value The originality of this paper is to use the lattice Boltzmann method in simulating the nanofluid flow and heat transfer within a cavity included with internal active bodies and fins.
      Citation: International Journal of Numerical Methods for Heat & Fluid Flow
      PubDate: 2018-12-14T10:55:49Z
      DOI: 10.1108/HFF-07-2018-0349
       
  • Effect of tilt angle on the multi-pipe channel with sinusoidal/curved
           walls – numerical modelling based on finite volume method
    • Abstract: International Journal of Numerical Methods for Heat & Fluid Flow, Ahead of Print.
      Purpose This paper aims to investigate the two-dimensional numerical modeling of fluid flow and heat transfer in a fluid channel. Design/methodology/approach The channel is filled with the CuO-water nanofluid. The KKL model is used to estimate the dynamic viscosity and considering Brownian motion. On the other hand, the influence of CuO nanoparticles’ shapes on the heat transfer rate is taken account in the simulations. The channel is included with several active pipes with hot and cold temperatures. Furthermore, the external curved and sinusoidal walls have cold and hot temperatures, respectively. Findings Three different tilt angles are considered with similar boundary and operating conditions. The Rayleigh numbers, solid volume fraction of CuO nanoparticles in the pure water and the tilt angles are the governing parameters. Different cases studies, such as streamlines, heat transfer rate, local and total entropy generation and heatlines, are analysed under influences of these governing parameters. Originality/value The originality of this work is investigation of fluid flow, heat transfer and entropy generation within a nanofluid filled channel using FVM.
      Citation: International Journal of Numerical Methods for Heat & Fluid Flow
      PubDate: 2018-12-31T08:07:02Z
      DOI: 10.1108/HFF-07-2018-0390
       
  • Numerical study on flow over a confined oscillating cylinder with a
           splitter plate
    • Abstract: International Journal of Numerical Methods for Heat & Fluid Flow, Ahead of Print.
      Purpose This study aims to investigate the effect of the simultaneous usage of active and passive methods (which in this case are rotational oscillation and attached splitter plate, respectively) on the flow and temperature fields to find an optimum situation which this combination results in heat transfer increment and drag reduction. Design/methodology/approach The method of the solution was based on finite volume discretization of Navier–Stokes equations. A dynamic grid is coupled with the solver by the arbitrary Lagrangian–Eulerian (ALE) formulation for modeling cylinder oscillation. Parametric studies were performed by altering oscillation frequency, splitter plate length and Reynolds number. Findings Oscillation in different frequencies was found to be complicated. Higher frequencies provide more heat transfer, but in the lock-on region, they bring remarkable increment to the drag coefficient. It was observed that simultaneous usage of oscillation and splitter plate may have both positive and negative effects on drag reduction and heat transfer increment. Finally F = 2 and L = 0.5 were chosen as an optimum combination. Originality/value In this study, the laminar incompressible flow and heat transfer from a confined rotationally oscillating circular cylinder with an attached splitter plate are investigated. Parametric studies are performed by changing oscillation frequency, splitter plate length and Reynolds number.
      Citation: International Journal of Numerical Methods for Heat & Fluid Flow
      PubDate: 2018-12-19T02:56:25Z
      DOI: 10.1108/HFF-06-2018-0286
       
  • MHD mixed convection of nanofluid due to an inner rotating cylinder in a
           3D enclosure with a phase change material
    • Abstract: International Journal of Numerical Methods for Heat & Fluid Flow, Ahead of Print.
      Purpose The purpose of this study is to numerically examine the mixed convection of CuO-water nanofluid due to a rotating inner hot circular cylinder in a 3D cubic enclosure with phase change material (PCM) attached to its vertical surface. Heat transfer and fluid flow characteristics were examined for various values of pertinent parameters. Design/methodology/approach Finite element method was used in the numerical simulation. Influence of various pertinent parameters such as Rayleigh number (between 10$^5$ and 10$^6$), Hartmann number (between 0 and 100), angular rotational speed of the cylinder (between −50 and 50), solid nanoparticle volume fraction (between 0 and 0.04) and PCM parameters (height-between 0.2H and 0.8H, thermal conductivity ratio- between 0.1 and 10) on the convective heat transfer characteristics are numerically studied. Findings It was observed that local heat transfer variations along the hot surface differ significantly for the cases with and without magnetic field where three distinct hot spots of peak Nusselt number are established when magnetic field is imposed. The average Nusselt number enhancement with the nanofluid at the highest particle volume fraction is 52.85 per cent at Hartmann number of 100, whereas its value is 39.76 per cent for the case in the absence of magnetic field. When the inner cylinder rotates, flow and thermal fields are affected within the cavity. The local heat transfer variations spread over the hot surface with cylinder rotation and 16.43 per cent of reduction in the average heat transfer is obtained with counter-clockwise rotation at 100 rad/sec. An enhancement in the PCM height and a reduction in the thermal conductivity of the PCM result in average heat transfer deterioration for the 3D cavity. The amount of the reduction is 43 per cent when the PCM height is increased from 0.2H to 0.8H, whereas 19.10 per cent enhancement in the heat transfer is achieved when thermal conductivity ratio (PCM) to the base fluid is increased from 0.1 to 10. Originality/value Such configurations can be designed for convection control, and in our case, various methods are available. Some of the investigated methods can be used in applications where magnetic field already exists. Convection control study in 3D cavity gives more realistic results as compared to 2D configurations, and results of the current investigation may be used for the design, optimization and flow control of many thermal applications involving magnetic field effects.
      Citation: International Journal of Numerical Methods for Heat & Fluid Flow
      PubDate: 2018-12-12T08:55:30Z
      DOI: 10.1108/HFF-07-2018-0364
       
  • Effects of discrete heat source location on heat transfer and entropy
           generation of nanofluid in an open inclined L-shaped cavity
    • Abstract: International Journal of Numerical Methods for Heat & Fluid Flow, Ahead of Print.
      Purpose This paper aims to concentrate on the impacts of a discrete heat source location on heat transfer and entropy generation for a Ag-water nanofluid in an open inclined L-shaped cavity. Design/methodology/approach The governing partial differential equations for this study are computed by the finite volume method. Findings The results show that increasing the inclination angle leads to a rise in heat transfer. It is clear with the increase in the nanoparticles volume fraction that the thermal performance reduces, and it increases when the inclination angle increases. Originality/value Because of the continuous literature survey, the authors have not found a study that concentrates on the entropy generation in a wide variety of irregular ducts. Thus, in this paper, they present the analysis of entropy generation in an L-shaped duct experiencing a mixed convective flow with a nanofluid. The authors deal with this geometry because it is very useful in cooling systems of nuclear and chemical reactors and electronic components.
      Citation: International Journal of Numerical Methods for Heat & Fluid Flow
      PubDate: 2018-12-10T12:26:54Z
      DOI: 10.1108/HFF-07-2018-0412
       
  • Heat transfer of incompressible flow in a rotating microchannel with slip
           boundary conditions of second order
    • Abstract: International Journal of Numerical Methods for Heat & Fluid Flow, Ahead of Print.
      Purpose The paper aims to consider heat transfer in incompressible flow in a rotating flat microchannel with allowance for boundary slip conditions of the first and second order. The novelty of the paper encompasses analytical and numerical solutions of the problem, with the latter based on the lattice Boltzmann method (LBM). The analytical solution of the problem includes relations for the velocity and temperature profiles and for the Nusselt number depending on the rotation rate of the microchannel and slip velocity. It was demonstrated that the velocity profiles at high rotation rates transform from parabolic to M-shaped with a minimum at the channel axis. The temperature profiles tend to become uniform (i.e. almost constant). An increase in the channel rotation rate contributes to the increase in the Nusselt number. An increase in the Prandtl number causes a similar effect. The trend caused by the effect of the second-order slip boundary conditions depends on the closure hypothesis. It is shown that heat transfer in a flat microchannel can be successfully modeled using the LBM methodology, which takes into account the second-order boundary conditions. Design/methodology/approach The paper is based on the comparisons of an analytical solution and a numerical solution, which employs the lattice Boltzmann method. Both mathematical approaches used the first-order and second-order slip boundary conditions. The results obtained using both methods agree well with each other. Findings The analytical solution of the problem includes relations for the velocity and temperature profiles and for the Nusselt number depending on the rotation rate of the microchannel and slip velocity. It was demonstrated that the velocity profiles at high rotation rates transform from parabolic to M-shaped with a minimum at the channel axis. The temperature profiles tend to become uniform (i.e. almost constant). The increase in the channel rotation rate contributes to the increase in the Nusselt number. An increase in the Prandtl number causes the similar effect. The trend caused by the effect of the second-order slip boundary conditions depends on the closure hypothesis. It is shown that heat transfer in a flat microchannel can be successfully modeled using the LBM methodology, which considers the second-order boundary conditions. Originality/value The novelty of the paper encompasses analytical and numerical solutions of the problem, whereas the latter are based on the LBM.
      Citation: International Journal of Numerical Methods for Heat & Fluid Flow
      PubDate: 2018-12-10T11:34:02Z
      DOI: 10.1108/HFF-06-2018-0264
       
  • Effects of two-phase nanofluid model on convection in a double lid-driven
           cavity in the presence of a magnetic field
    • Abstract: International Journal of Numerical Methods for Heat & Fluid Flow, Ahead of Print.
      Purpose The aim of this study is to investigate the effects of two-phase nanofluid model on mixed convection in a double lid-driven square cavity in the presence of a magnetic field. The authors believe that this work is a good contribution for improving the thermal performance and the heat transfer enhancement in some engineering instruments. Design/methodology/approach The current work investigates the problem of mixed convection heat transfer in a double lid-driven square cavity in the presence of magnetic field. The used cavity is filled with water-Al2O3 nanofluid based on Buongiorno’s two-phase model. The bottom horizontal wall is maintained at a constant high temperature and moves to the left/right, while the top horizontal wall is maintained at a constant low temperature and moves to the right/left. The left and right vertical walls are thermally insulated. The dimensionless governing equations are solved numerically using the Galerkin weighted residual finite element method. Findings The obtained results show that the heat transfer rate enhances with an increment of Reynolds number or a reduction of Hartmann number. In addition, effects of thermophoresis and Brownian motion play a significant role in the growth of convection heat transfer. Originality/value According to above-mentioned studies and to the authors’ best knowledge, there has no study reported the MHD mixed convection heat transfer in a double lid-driven cavity using the two-phase nanofluid model. Thus, the authors of the present study believe that this work is valuable. Therefore, the aim of this comprehensive numerical study is to investigate the effects of two-phase nanofluid model on mixed convection in a double lid-driven square cavity in the presence of a magnetic field. The authors believe that this work is a good contribution for improving the thermal performance and the heat transfer enhancement in some engineering instruments.
      Citation: International Journal of Numerical Methods for Heat & Fluid Flow
      PubDate: 2018-12-10T08:55:34Z
      DOI: 10.1108/HFF-07-2018-0386
       
  • Numerical analysis of mixed convection of different nanofluids in
           concentric annulus
    • Abstract: International Journal of Numerical Methods for Heat & Fluid Flow, Ahead of Print.
      Purpose This study aims to investigate the numerical analysis of mixed convection within the horizontal annulus in the presence of water-based fluid with nanoparticles of aluminum oxide, copper, silver and titanium oxide. Numerical solution is performed using a finite-volume method based on the SIMPLE algorithm, and the discretization of the equations is generally of the second order. Inner and outer cylinders have a constant temperature, and the inner cylinder temperature is higher than the outer one. The two cylinders can be rotated in both directions at a constant angular velocity. The effect of parameters such as Rayleigh, Richardson, Reynolds and the volume fraction of nanoparticles on heat transfer and flow pattern are investigated. The results show that the heat transfer rate increases with the increase of the Rayleigh number, as well as by increasing the volume fraction of the nanoparticles, the heat transfer rate increases, and this increase is about 8.25 per cent for 5 per cent volumetric fraction. Rotation of the cylinders reduces the overall heat transfer. Different directions of rotation have a great influence on the flow pattern and isotherms, and ultimately on heat transfer. The addition of nanoparticles does not have much effect on the flow pattern and isotherms, but it is quantitatively effective. The extracted results are in good agreement with previous works. Design/methodology/approach Studying mixed convection heat transfer in the horizontal annulus in the presence of a water-based fluid with aluminum oxide, copper, silver and titanium oxide nanoparticles is carried out quantitatively using a finite-volume method based on the SIMPLE algorithm. Findings Increasing the Rayleigh number increases the Nusselt number. Increasing the Richardson number increases heat transfer. Adding nanoparticles does not have much effect on the flow pattern but is effective quantitatively on heat transfer parameters. The addition of nanoparticles sometimes increases the heat transfer rate by about 8.25 per cent. In constant Rayleigh numbers, increasing the Reynolds number reduces heat transfer. The Rayleigh and Reynolds numbers greatly affect the isotherms and streamlines. In addition to the thermal conductivity of nanoparticles, the thermo-physical properties of nanoparticles has great effect in the formation of isotherms and streamlines and ultimately heat transfer. Originality/value Studying the effect of different direction of rotation on the isotherms and streamlines, as well as the comparison of different nanoparticles on mixed convection heat transfer in annulus.
      Citation: International Journal of Numerical Methods for Heat & Fluid Flow
      PubDate: 2018-12-10T08:46:37Z
      DOI: 10.1108/HFF-06-2018-0337
       
  • Unsteady natural convection in a partially porous cavity having a
           heat-generating source using local thermal non-equilibrium model
    • Abstract: International Journal of Numerical Methods for Heat & Fluid Flow, Ahead of Print.
      Purpose The purpose of this study is a numerical analysis of transient natural convection in a square partially porous cavity with a heat-generating and heat-conducting element using the local thermal non-equilibrium model under the effect of cooling from the vertical walls. It should be noted that this research deals with a development of passive cooling system for the electronic devices. Design/methodology/approach The domain of interest is a square cavity with a porous layer and a heat-generating element. The vertical walls of the cavity are kept at constant cooling temperature, while the horizontal walls are adiabatic. The heat-generating solid element is located on the bottom wall. A porous layer is placed under the clear fluid layer. The governing equations, formulated in dimensionless stream function, vorticity and temperature variables with corresponding initial and boundary conditions, are solved using implicit finite difference schemes of the second order accuracy. The governing parameters are the Darcy number, viscosity variation parameter, porous layer height and dimensionless time. The effects of varying these parameters on the average total Nusselt number along the heat source surface, the average temperature of the heater, the fluid flow rate inside the cavity and on the streamlines and isotherms are analyzed. Findings The results show that in the case of local thermal non-equilibrium the total average Nusselt number is an increasing function of the interphase heat transfer coefficient and the porous layer thickness, while the average heat source temperature decreases with the Darcy number and viscosity variation parameter. Originality/value An efficient numerical technique has been developed to solve this problem. The originality of this work is to analyze unsteady natural convection within a partially porous cavity using the local thermal non-equilibrium model in the presence of a local heat-generating solid element. The results would benefit scientists and engineers to become familiar with the analysis of convective heat transfer in enclosures with local heat-generating heaters and porous layers, and the way to predict the heat transfer rate in advanced technical systems, in industrial sectors including transportation, power generation, chemical sectors and electronics.
      Citation: International Journal of Numerical Methods for Heat & Fluid Flow
      PubDate: 2018-12-06T02:51:21Z
      DOI: 10.1108/HFF-06-2018-0338
       
  • Modeling and analysis of solar air channels with attachments of different
           shapes
    • Abstract: International Journal of Numerical Methods for Heat & Fluid Flow, Ahead of Print.
      Purpose This paper aims to report the results of numerical analysis of turbulent fluid flow and forced-convection heat transfer in solar air channels with baffle-type attachments of various shapes. The effect of reconfiguring baffle geometry on the local and average heat transfer coefficients and pressure drop measurements in the whole domain investigated at constant surface temperature condition along the top and bottom channels’ walls is studied by comparing 15 forms of the baffle, which are simple (flat rectangular), triangular, trapezoidal, cascaded rectangular-triangular, diamond, arc, corrugated, +, S, V, double V (or W), Z, T, G and epsilon (or e)-shaped, with the Reynolds number changing from 12,000 to 32,000. Design/methodology/approach The baffled channel flow model is controlled by the Reynolds-averaged Navier–Stokes equations, besides the k-epsilon (or k-e) turbulence model and the energy equation. The finite volume method, by means of commercial computational fluid dynamics software FLUENT is used in this research work. Findings Over the range investigated, the Z-shaped baffle gives a higher thermal enhancement factor than with simple, triangular, trapezoidal, cascaded rectangular-triangular, diamond, arc, corrugated, +, S, V, W, T, G and e-shaped baffles by about 3.569-20.809; 3.696-20.127; 3.916-20.498; 1.834-12.154; 1.758-12.107; 7.272-23.333; 6.509-22.965; 8.917-26.463; 8.257-23.759; 5.513-18.960; 8.331-27.016; 7.520-26.592; 6.452-24.324; and 0.637-17.139 per cent, respectively. Thus, the baffle of Z-geometry is considered as the best modern model of obstacles to significantly improve the dynamic and thermal performance of the turbulent airflow within the solar channel. Originality/value This analysis reports an interesting strategy to enhance thermal transfer in solar air channels by use of attachments with various shapes
      Citation: International Journal of Numerical Methods for Heat & Fluid Flow
      PubDate: 2018-12-04T02:32:10Z
      DOI: 10.1108/HFF-08-2018-0435
       
  • Dual-position excitation technique in flow control over an airfoil at low
           speeds
    • Abstract: International Journal of Numerical Methods for Heat & Fluid Flow, Ahead of Print.
      Purpose The purpose of this paper is to control flow separation over a NACA 4415 airfoil by applying unsteady forces to the separated shear layers using dielectric barrier discharge (DBD) plasma actuators. This novel flow control method is studied under conditions which the airfoil angle of attack is 18°, and Reynolds number based on chord length is 5.5 × 105. Design/methodology/approach Large eddy simulation of the turbulent flow is used to capture vortical structures through the airfoil wake. Power spectral density analysis of the baseline flow indicates dominant natural frequencies associated with “shear layer mode” and “wake mode.” The wake mode frequency is used simultaneously to excite separated shear layers at both the upper surface and the trailing edge of the airfoil (dual-position excitation), and it is also used singly to excite the upper surface shear layer (single-position excitation). Findings Based on the results, actuations manipulate the shear layers instabilities and change the wake patterns considerably. It is revealed that in the single-position excitation case, the vortices shed from the upper surface shear layer are more coherent than the dual-position excitation case. The maximum value of lift coefficient and lift-to-drag ratio is achieved, respectively, by single-position excitation as well as dual-position excitation. Originality/value The paper contributes to the understanding and progress of DBD plasma actuators for flow control applications. Further, this research could be a beneficial solution for the promising design of advanced low speed flying vehicles.
      Citation: International Journal of Numerical Methods for Heat & Fluid Flow
      PubDate: 2018-12-04T02:28:10Z
      DOI: 10.1108/HFF-05-2018-0195
       
  • Effect of wall-mounted V-baffle position in a turbulent flow through a
           channel
    • Abstract: International Journal of Numerical Methods for Heat & Fluid Flow, Ahead of Print.
      Purpose The purpose of this paper is to carry out a numerical study on the dynamic and thermal behavior of a fluid with a constant property and flowing turbulently through a two-dimensional horizontal rectangular channel. The upper surface was put in a constant temperature condition, while the lower one was thermally insulated. Two transverse, solid-type obstacles, having different shapes, i.e. flat rectangular and V-shaped, were inserted into the channel and fixed to the top and bottom walls of the channel, in a periodically staggered manner to force vortices to improve the mixing, and consequently the heat transfer. The flat rectangular obstacle was put in the first position and was placed on the hot top wall of the channel. However, the second V-shaped obstacle was placed on the insulated bottom wall, at an attack angle of 45°; its position was varied to find the optimum configuration for optimal heat transfer. Design/methodology/approach The fluid is considered Newtonian, incompressible with constant properties. The Reynolds averaged Navier–Stokes equations, along with the standard k-epsilon turbulence model and the energy equation, are used to control the channel flow model. The finite volume method is used to integrate all the equations in two-dimensions; the commercial CFD software FLUENT along with the SIMPLE-algorithm is used for pressure-velocity coupling. Various values of the Reynolds number and obstacle spacing were selected to perform the numerical runs, using air as the working medium. Findings The channel containing the flat fin and the 45° V-shaped baffle with a large Reynolds number gave higher heat transfer and friction loss than the one with a smaller Reynolds number. Also, short separation distances between obstacles provided higher values of the ratios Nu/Nu0 and f/f0 and a larger thermal enhancement factor (TEF) than do larger distances. Originality/value This is an original work, as it uses a novel method for the improvement of heat transfer in completely new flow geometry.
      Citation: International Journal of Numerical Methods for Heat & Fluid Flow
      PubDate: 2018-12-04T02:19:33Z
      DOI: 10.1108/HFF-06-2018-0270
       
  • Potential of gear-ring turbulator in three-dimensional heat exchanger tube
           from second law of thermodynamic viewpoint
    • Abstract: International Journal of Numerical Methods for Heat & Fluid Flow, Ahead of Print.
      Purpose This paper aims to use the second law of thermodynamic to evaluate the potential of gear-ring turbulator in a three-dimensional heat exchanger tube. Accordingly, a numerical simulation is performed to obtain the irreversibilities in a three-dimensional heat exchanger tube equipped with some gear-ring turbulators for turbulence regime. Design/methodology/approach A numerical simulation is performed to obtain the irreversibilities in a three-dimensional heat exchanger tube equipped with some gear-ring turbulators for turbulence regime. The analysis is carried out based on shear stress transport (SST) k-ω turbulent model. The influences of different parameters containing tooth number, free-space length ratios and Reynolds number on frictional and thermal irreversibilities and Bejan number are discussed. Findings The results indicated that the thermal irreversibility reduces by decreasing the tooth number. For example, the thermal entropy generation decreases about 25.81 per cent by decreasing the tooth number in the range of 24 to 0 at Re = 6,000. Moreover, the frictional entropy generation decreases by increasing the tooth number as the gear with more tooth number causes a lower flow disturbance. Originality/value The present study arranged a numerical work to study the potential of a gear-ring turbulator in a heat exchanger tube from first and second laws of thermodynamic viewpoint. The turbulent flow is considered for this problem. The literature review showed that the usage of a gear-ring turbulator in a heat exchanger tube is not investigated from the second law of thermodynamic viewpoint by previous studies. As a result, the influences of different parameters containing tooth number, free-space length ratios and Reynolds number on frictional and thermal irreversibilities and Bejan number are discussed.
      Citation: International Journal of Numerical Methods for Heat & Fluid Flow
      PubDate: 2018-12-04T02:18:29Z
      DOI: 10.1108/HFF-05-2018-0250
       
  • Slip velocity and temperature jump of a non-Newtonian nanofluid, aqueous
           solution of carboxy-methyl cellulose/aluminum oxide nanoparticles, through
           a microtube
    • Abstract: International Journal of Numerical Methods for Heat & Fluid Flow, Ahead of Print.
      Purpose With respect to two new subjects, i.e. nanofluids and microchannels, in heat transfer systems and modern techniques used for building them, this paper aims to study on effect of using aluminum oxide nanoparticles in non-Newtonian fluid of aqueous solution of carboxy-methyl cellulose in microtube and through application of different slip coefficients to achieve various qualities on surface of microtube. Design/methodology/approach Simultaneously, the effect of presence of nanoparticles and phenomenon of slip and temperature jump has been explored in non-Newtonian nanofluid in this essay. The assumption of homogeneity of nanofluid and fixed temperature of wall in microtube has been used in modeling processes. Findings The results have been presented as diagrams of velocity, temperature and Nusselt Number and the investigations have indicated that addition of nanoparticles to the base fluid and increase in microtube slip coefficient might improve rate of heat transfer in microtube. Originality/value The flow of non-Newtonian nanofluid of aqueous solution of carboxy methyl cellulose-aluminum oxide has been determined in a microtube for the first time.
      Citation: International Journal of Numerical Methods for Heat & Fluid Flow
      PubDate: 2018-12-04T02:18:08Z
      DOI: 10.1108/HFF-05-2018-0192
       
  • Effect of magnetic field-dependent thermal conductivity on natural
           convection of magnetic nanofluid inside a square enclosure
    • Abstract: International Journal of Numerical Methods for Heat & Fluid Flow, Ahead of Print.
      Purpose The purpose of this paper is to investigate the convective heat transfer of magnetic nanofluid (MNF) inside a square enclosure under uniform magnetic fields considering nonlinearity of magnetic field-dependent thermal conductivity. Design/methodology/approach The properties of the MNF (Fe3O4+kerosene) were described by polynomial functions of magnetic field-dependent thermal conductivity. The effect of the transverse magnetic field (0 < H < 105), Hartmann Number (0 < Ha < 60), Rayleigh number (10
      Citation: International Journal of Numerical Methods for Heat & Fluid Flow
      PubDate: 2018-11-28T03:26:53Z
      DOI: 10.1108/HFF-07-2018-0374
       
  • Bioconvection in nanofluid-saturated porous square cavity containing
           oxytactic microorganisms
    • Abstract: International Journal of Numerical Methods for Heat & Fluid Flow, Ahead of Print.
      Purpose The purpose of this paper is to investigate the bioconvection flow in a porous square cavity saturated with both oxytactic microorganism and nanofluids. Design/methodology/approach The impacts of the effective parameters such as Rayleigh number, bioconvection number, Peclet number and thermophoretic force, Brownan motion and Lewis number reduces the flow strength in the cavity on the flow strength, oxygen density distribution, motile isoconcentrations and heat transfer performance are investigated using a finite volume approach. Findings The results obtained showed that the average Nusselt number is increased with Peclet number, Lewis number, Brownian motion and thermophoretic force. Also, the average Sherwood number increased with Brownian motion and Peclet number and decreased with thermophoretic force. It is concluded that the flow strength is pronounced with Rayleigh number, bioconvection number, Peclet number and thermophoretic force. Brownan motion and Lewis number reduce the flow strength in the cavity. Originality/value There is no published study in the literature about sensitivity analysis of Brownian motion and thermophoresis force effects on the bioconvection heat transfer in a square cavity filled by both nanofluid and oxytactic microorganisms.
      Citation: International Journal of Numerical Methods for Heat & Fluid Flow
      PubDate: 2018-11-27T01:39:39Z
      DOI: 10.1108/HFF-05-2018-0238
       
  • Simulation the effects of cross-flow injection on the slip velocity and
           temperature domain of a nanofluid flow inside a microchannel
    • Abstract: International Journal of Numerical Methods for Heat & Fluid Flow, Ahead of Print.
      Purpose In this paper, the forced convection heat transfer of the nanofluid composed of water and AL2O3 nanoparticles is simulated in a two-dimensional horizontal microchannel by injecting the lower wall. The upper wall of the microchannel is 303 K at temperature TH. On the lower wall of the microchannel, there are three holes for flow injection. Other parts of the wall are insulated. In this paper, the effect of parameters such as Reynolds number, slip coefficient and volume fraction of nanoparticles is investigated. Design/methodology/approach The boundary condition of the slip velocity is considered on the upper and lower walls of the microchannel. In this work, the flow of nanofluid in the microchannel is considered to be slow, permanent and Newtonian. In the present study, the effect of injection through the microchannel wall on the slip velocity is examined for the first time. Findings The results are also presented as velocity profiles and Nusselt number diagrams. It was found that the Nusselt number increases with increasing the amount of slip coefficient of velocity and the weight percentage of solid nanoparticles. The rate of this increase is higher in the high values of the Reynolds number. Originality/value A novel paper concerned the simulation of cross-flow injection effects on the slip velocity and temperature domain of a nanofluid flow inside a microchannel.
      Citation: International Journal of Numerical Methods for Heat & Fluid Flow
      PubDate: 2018-11-22T03:22:21Z
      DOI: 10.1108/HFF-04-2018-0149
       
  • Impact of partial slip on mixed convective flow towards a Riga plate
           comprising micropolar TiO2-kerosene/water nanoparticles
    • Abstract: International Journal of Numerical Methods for Heat & Fluid Flow, Ahead of Print.
      Purpose The purpose of this paper is to present an inclusive study of the mixed convective flow involving micropolar fluid holding kerosene/water-based TiO2 nanoparticle towards a vertical Riga surface with partial slip. The outcomes are confined for opposing and assisting flows. Design/methodology/approach Similarity equations are acquired and then worked out numerically by the Keller box technique. Findings Impacts of significant parameters on microrotation velocity, temperature distribution, velocity profile together with the Nusselt number and the skin friction are argued with the help of graphs. Two solutions are achieved in opposing flow, while the solution is unique in assisting flow. It is also monitored that the separation of boundary layer delays because of micropolar parameter and accelerates because of volume fraction. Originality/value The authors trust that all these results are new and significant for researchers.
      Citation: International Journal of Numerical Methods for Heat & Fluid Flow
      PubDate: 2018-11-06T10:58:54Z
      DOI: 10.1108/HFF-06-2018-0258
       
  • Investigating the effect of nanoparticles diameter on turbulent flow and
           heat transfer properties of non-Newtonian carboxymethyl cellulose/CuO
           fluid in a microtube
    • Abstract: International Journal of Numerical Methods for Heat & Fluid Flow, Ahead of Print.
      Purpose Although many studies have been conducted on the nanofluid flow in microtubes, this paper, for the first time, aims to investigate the effects of nanoparticle diameter and concentration on the velocity and temperature fields of turbulent non-Newtonian Carboxymethylcellulose (CMC)/copper oxide (CuO) nanofluid in a three-dimensional microtube. Modeling has been done using low- and high-Reynolds turbulent models. CMC/CuO was modeled using power law non-Newtonian model. The authors obtained interesting results, which can be helpful for engineers and researchers that work on cooling of electronic devices such as LED, VLSI circuits and MEMS, as well as similar devices. Design/methodology/approach Present numerical simulation was performed with finite volume method. For obtaining higher accuracy in the numerical solving procedure, second-order upwind discretization and SIMPLEC algorithm were used. For all Reynolds numbers and volume fractions, a maximum residual of 10−6 is considered for saving computer memory usage and the time for the numerical solving procedure. Findings In constant Reynolds number and by decreasing the diameter of nanoparticles, the convection heat transfer coefficient increases. In Reynolds numbers of 2,500, 4,500 and 6,000, using nanoparticles with the diameter of 25 nm compared with 50 nm causes 0.34 per cent enhancement of convection heat transfer coefficient and Nusselt number. Also, in Reynolds number of 2,500, by increasing the concentration of nanoparticles with the diameter of 25 nm from 0.5 to 1 per cent, the average Nusselt number increases by almost 0.1 per cent. Similarly, In Reynolds numbers of 4,500 and 6,000, the average Nusselt number increases by 1.8 per cent. Research limitations/implications The numerical simulation was carried out for three nanoparticle diameters of 25, 50 and 100 nm with three Reynolds numbers of 2,500, 4,500 and 6,000. Constant heat flux is on the channel, and the inlet fluid becomes heated and exists from it. Practical implications The authors obtained interesting results, which can be helpful for engineers and researchers that work on cooling of electronic devices such as LED, VLSI circuits and MEMS, as well as similar devices. Originality/value This manuscript is an original work, has not been published and is not under consideration for publication elsewhere. About the competing interests, the authors declare that they have no competing interests.
      Citation: International Journal of Numerical Methods for Heat & Fluid Flow
      PubDate: 2018-10-30T02:02:20Z
      DOI: 10.1108/HFF-07-2018-0368
       
  • Three-dimensional combined radiation-magnetoconvection of low electrically
           conductive dielectric oxide melt
    • Abstract: International Journal of Numerical Methods for Heat & Fluid Flow, Ahead of Print.
      Purpose The purpose of this paper is to investigate the coupled effect of magnetic field and radiation on convective heat transfer of low electrically conductive dielectric oxide melt. Design/methodology/approach The 3D Navier–Stokes equations are formulated using the vector potential-vorticity formulation and solved using the finite volume method (FVM). The radiative heat transfer equation is discretized using the FTnFVM method. A code was written using FORTRAN language. Findings The obtained numerical results are focused on the effect of the different parameters on the heat transfer and the flow structure with a special interest on the 3D transvers flow. It is found that the flow is developing in inner spirals and the magnetic field intensifies this 3D character. The radiation acts mainly at the core of the enclosure and causes the apparition of the merging phenomenon near the front and back walls. Originality/value The effect of magnetic field on convective heat transfer of highly electrically conductive fluids has been intensively studied. Reciprocally, the case of a fluid with low electrical conductivity is not so much investigated, especially when it is coupled with the effect of radiation. These two effects are studied in this paper for the case of a low-conductive LiNbO3 oxide melt.
      Citation: International Journal of Numerical Methods for Heat & Fluid Flow
      PubDate: 2018-10-26T12:41:02Z
      DOI: 10.1108/HFF-06-2018-0263
       
  • Investigation of laminar fluid flow and heat transfer of nanofluid in
           trapezoidal microchannel with different aspect ratios
    • Abstract: International Journal of Numerical Methods for Heat & Fluid Flow, Ahead of Print.
      Purpose In the present study, laminar steady flow of nanofluid through a trapezoidal channel is studied by using of finite volume method. The main aim of this paper is to study the effect of changes in geometric parameters, including internal and external dimensions on the behavior of heat transfer and fluid flow. For each parameter, an optimum ratio will be presented. Design/methodology/approach The results showed that in a channel cell, changing any geometric parameter may affect the temperature and flow field, even though the volume of the channel is kept constant. For a relatively small hydraulic diameter, microchannels with different angles have a similar dimensionless heat flux, while channels with bigger dimensions show various values of dimensionless heat flux. By increasing the angles of trapezoidal microchannels, dimensionless heat flux per unit of volume increases. As a result, the maximum and minimum heat transfer rate occurs in a trapezoidal microchannel with 75° and 30 internal’s, respectively. In the study of dimensionless heat flux rate with hydraulic diameter variations, an optimum hydraulic diameter (Dh) was observed in which the heat transfer rate per unit volume attains maximum value. Findings This optimum state is predicted to happen at a side angle of 75° and hydraulic diameter of 290 µm. In addition, in trapezoidal microchannel with higher aspect ratio, dimensionless heat flux rate is lower. Changing side angles of the channels and pressure drop have the same effect on pressure drop. For a constant pressure drop, if changing the side angles causes an increase in the rectangular area of the channel cross-section and the effect of the sides are not felt by the fluid, then the dimensionless heat flux will increase. By increasing the internal aspect ratio (t_2/t_3), the amount of t_3 decreases, and consequently, the conduction resistance of the hot surface decreases. Originality/value The effects of geometry of the microchannel, including internal and external dimensions on the behavior of heat transfer and fluid flow for pressure ranges between 2 and 8 kPa.
      Citation: International Journal of Numerical Methods for Heat & Fluid Flow
      PubDate: 2018-10-24T08:18:30Z
      DOI: 10.1108/HFF-05-2018-0231
       
  • Effect of MHD on the flow and heat transfer characteristics of nanofluid
           in a grooved channel with internal heat generation
    • Abstract: International Journal of Numerical Methods for Heat & Fluid Flow, Ahead of Print.
      Purpose The purpose of this study is numerical simulation of magnetohydrodynamics (MHD) water–Al2O3 nanofluid mixed convection in a grooved channel with internal heat generation in solid cylinders. Simulations were carried out at Reynolds numbers 50 ≤ Re ≤ 100, Hartmann numbers 0 ≤ Ha ≤ 15, Grashof numbers 5,000 ≤ Gr ≤ 10−4 and volume fraction 0 ≤ φ ≤ 0.04. The effect of Reynolds number and the influence of magnetic field and pressure drop on convective heat transfer coefficient were studied in different volume fractions of nanoparticles at different Reynolds numbers. Design/methodology/approach The results show that average Nusselt number increases by increasing Reynolds and Hartman numbers. Also, when Hartman number increases, velocity profile becomes asymmetric. Pressure distribution shows that magnetic field applies Lorentz force at opposite direction of the flow, which causes asymmetric distribution of pressure. As a result, pressure in the upper half of the cylinder is higher than the lower half. Finally, velocity and temperature contours along the channel for different Hartmann numbers, volume fraction 3 per cent, Re = 50 and 100 and Gr = 10,000, are presented. Findings The effect of Reynolds number and the influence of magnetic field and pressure drop on convective heat transfer coefficient were studied in different volume fractions of nanoparticles at different Reynolds numbers. Originality/value Effect of MHD on the flow and heat transfer characteristics of Water–Al2O3 nanofluid in a grooved channel with internal heat generation in solid cylinders.
      Citation: International Journal of Numerical Methods for Heat & Fluid Flow
      PubDate: 2018-10-17T12:31:31Z
      DOI: 10.1108/HFF-05-2018-0235
       
  • Heat transfer enhancement in solidification process by change of fins
           arrangements in a heat exchanger containing phase-change materials
    • Abstract: International Journal of Numerical Methods for Heat & Fluid Flow, Ahead of Print.
      Purpose Reducing discrepancy between energy demand and supply has been a controversial issue among researchers. Thermal energy storage is a technique to decrease this difference to increase the thermal efficiency of systems. Latent heat thermal energy storage has interested many researchers over the past few decades because of its high thermal energy density and constant operating temperature. The purpose of this paper is to provide a numerical study of the solidification process in a triplex tube heat exchanger containing phase change material (PCM) RT82. Design/methodology/approach A two-dimensional transient model was generated using finite volume method and regarding enthalpy-porosity technique. After that, a detailed and systematic approach has been presented to modify longitudinal fins’ configuration to enhance heat transfer rate in PCMs and reducing solidification time. The numerical results of this study have been validated by reference experimental results. Findings The ultimate model reduced solidification time up to 21.1 per cent of the Reference model which is a substantial improvement. Moreover, after testing different arrangements of rectangular fins and studying the flow pattern of liquid PCM during solidification, two general criteria was introduced so that engineers can reach the highest rate of heat transfer for a specified value of total surface area of fins. Finally, the effect of considering natural convection during solidification was studied, and the results showed that disregarding natural convection slows down the solidification process remarkably in comparison with experimental results and in fact, this assumption generates non-real estimation of solidification process. Originality/value The arrangement of the fins to have the best possible solidification time is the novelty in this paper.
      Citation: International Journal of Numerical Methods for Heat & Fluid Flow
      PubDate: 2018-10-17T01:25:24Z
      DOI: 10.1108/HFF-06-2018-0333
       
  • Magneto-hydrodynamic natural convection of CuO-water nanofluid in complex
           shaped enclosure considering various nanoparticle shapes
    • Abstract: International Journal of Numerical Methods for Heat & Fluid Flow, Ahead of Print.
      Purpose The purpose of this study is to peruse natural convection in a CuO-water nanofluid-filled complex-shaped enclosure under the influence of a uniform magnetic field by using control volume finite element method. Design/methodology/approach Governing equations formulated in dimensionless stream function, vorticity and temperature variables using the single-phase nanofluid model with the Koo–Kleinstreuer–Li correlation for the effective dynamic viscosity and the effective thermal conductivity have been solved numerically by control volume finite element method. Findings Effects of various pertinent parameters such as Rayleigh number, Hartmann number, volume fraction of nanofluid and shape factor of nanoparticle on the convective heat transfer characteristics are analysed. It was observed that local and average heat transfer rates increase for higher value of Rayleigh number and lower value of Hartmann number. Among various nanoparticle shapes, platelets were found to be best in terms of heat transfer performance. The amount of average Nusselt number reductions was found to be different when nanofluids with different solid particle volume fractions were considered due to thermal and electrical conductivity enhancement of fluid with nanoparticle addition. Originality/value A comprehensive study of the natural convection in a CuO-water nanofluid-filled complex-shaped enclosure under the influence of a uniform magnetic field by using control volume finite element method is addressed.
      Citation: International Journal of Numerical Methods for Heat & Fluid Flow
      PubDate: 2018-10-17T01:23:22Z
      DOI: 10.1108/HFF-06-2018-0294
       
  • Heat generating porous matrix effects on Brownian motion of nanofluid
    • Abstract: International Journal of Numerical Methods for Heat & Fluid Flow, Ahead of Print.
      Purpose The purpose of this study is to indicate the effect of mounting heat generating porous matrix in a close cavity on the Brownian term of CuO-water nanofluid and its impact on improving the Nusselt number. Design/methodology/approach Because of the presence of heat source in porous matrix, couple of energy equations is solved for porous matrix and nanofluid separately. Thermal conductivity and viscosity of nanofluid were assumed to be consisting of a static component and a Brownian component that were functions of volume fraction of the nanofluid and temperature. To explain the effect of the Brownian term on the flow and heat fields, different parameters such as heat conduction ratio, interstitial heat transfer coefficient, Rayleigh number, concentration of nanoparticles and porous material porosity were investigated and compared to those of the non-Brownian solution. Findings The Brownian term caused the cooling of porous matrix because of rising thermal conductivity. Mounting the porous material into cavity changes the temperature distribution and increases Brownian term effect and heat transfer functionality of the nanofluid. Besides, the effect of the Brownian term was seen to be greatest at low Rayleigh number, low-porosity and small thermal conductivity of the porous matrix. It is noteworthy that because of decrement of thermal conduction in high porosities, the impact of Brownian term drops severely making it possible to obtain reliable results even in the case of neglecting Brownian term in these porosities. Originality/value The effect of mounting the porous matrix with internal heat generation was investigated on the improvement of variable properties of nanofluid.
      Citation: International Journal of Numerical Methods for Heat & Fluid Flow
      PubDate: 2018-10-15T02:44:28Z
      DOI: 10.1108/HFF-02-2018-0068
       
  • Heat transfer enhancement of circular and square LED geometry
    • Abstract: International Journal of Numerical Methods for Heat & Fluid Flow, Ahead of Print.
      Purpose The purpose of this paper is to compare the thermal effect between square and circular geometry of light emitting diode (LED) with respect of the same surface for the intent of reducing the junction temperature. Design/methodology/approach The heat equation is presented in a dimensionless form. To solve it numerically subject to the boundary conditions, the authors realized a three-dimensional code with Comsol Multiphysics. Findings The model is validated with previously published works. The authors found a good agreement. Originality/value New design of heat sink is improved for circular LED and a reduction of 18 per cent of the junction temperature is permitted. The authors study the influence of various parameters: number and length of fins and number and width of splits. New distribution of multichip LED in circular geometry permits to put 42 chips instead of 36 chips with respect of the same surface and pitch and with reduction of the junction temperature by 16 per cent.
      Citation: International Journal of Numerical Methods for Heat & Fluid Flow
      PubDate: 2018-10-12T01:00:25Z
      DOI: 10.1108/HFF-04-2018-0172
       
  • 3D numerical analysis of atmospheric-aerosol/carbon-black nanofluid flow
           within a solar air heater located in Shiraz, Iran
    • Abstract: International Journal of Numerical Methods for Heat & Fluid Flow, Ahead of Print.
      Purpose In this study, the effects of using corrugated absorber plate (instead of flat plate) and also using aerosol/carbon-black nanofluid (instead of air) on heat transfer and turbulent flow characteristics in solar collectors were numerically investigated. Design/methodology/approach The 3D continuity, momentum and energy equation were solved by finite volume and SIMPLE algorithm. As a result, the corrugated absorber plate was inspected in the case of triangle, rectangle and sinuous with the wave length of 1 mm and wave amplitude of 3 mm in turbulent flow regime and Reynolds number between 2,500 and 4,000. Choosing the proper geometry was carried out based on the best performance evaluation criteria (PEC) and increasing the air temperature from collector inlet to outlet. Findings The results revealed that for all times of the year the highest PEC was obtained for corrugated Sinusoidal model; however, the highest temperature increase from inlet to outlet was obtained for rectangular corrugated model. In addition, the results indicated that in sinusoidal model, the nanoparticles volume fractions increase leads to heat performance coefficient increase and the best heat performance conditions were attained in volume fraction of 0.1 per cent and Reynolds number of 4,000 for both six months period. In model with rectangular corrugated plate, usage of nanofluid in all range of Reynolds numbers leads to reduction of outlet temperature. Originality/value The effect of some nanoparticles on heat transfer using thermal– hydraulic performances in heat exchangers has been assessed, but the effects of atmospheric aerosol-based nanofluid using carbon-black nanoparticles (CBNPs) on the heat transfer in corrugated heat sink solar collectors by 3D numerical modeling has not been yet investigated. In present study, usage of CBNPs with different volume fractions in range of 0 to 0.1 per cent in turbulent regime of fluid flow is analyzed. Furthermore, in this paper, besides the effects of using CBNPs, a solar absorber located in Shiraz, as one of the best solar irradiation receiver cities in Iran is evaluated.
      Citation: International Journal of Numerical Methods for Heat & Fluid Flow
      PubDate: 2018-10-11T10:14:03Z
      DOI: 10.1108/HFF-04-2018-0169
       
  • Experimental and numerical investigations of thermal performance of
           Al2O3/water nanofluid for a combi boiler with double heat exchangers
    • Abstract: International Journal of Numerical Methods for Heat & Fluid Flow, Ahead of Print.
      Purpose This study aims to focus on usage of Al2O3/water nanofluid as working fluid in a combi boiler. The plate heat exchanger located at the bottom of the combi boiler has been used for heating the domestic water in the present study. Al2O3/water nanofluid has also been used in obtaining of the heat energy provided from combustion. Therefore, thermal performance of Al2O3/water has been determined by comparing water and nanofluid-water mixture. The present study also investigates heat transfer rates as numerical and experimental for varying cold side outlet temperatures, comparatively. Design/methodology/approach The present study has included both experimental and numerical methodologies. The experimental setup consists of main heat exchanger, atmospheric burner, circulation pump and plate-type heat exchanger in which the Al2O3/water nanofluid was used as working fluid to heat the domestic water. In the numerical part of the study, a commercial computational fluid dynamic code has been used to model heat rate and thermal efficiency of the heat exchanger used. Findings It has been concluded that the predicted results are in satisfactorily good agreement with the measured data. In the experimental part of the study, the flow rate of Al2O3/water nanofluid was kept constant during the experiments. The flow rates of the water by which the heated Al2O3/water nanofluid mixture was cooled via the plate heat exchanger have been changed as 3, 4, 5 and 6 lpm. The domestic water temperatures that were kept constant have also been changed as 40°C, 45°C, 50°C, 55°C and 60°C. It has been concluded that the Al2O3/water nanofluid thermal efficiency has been 16 per cent better than pure water. Originality/value The main originality of the present study is that thermal efficiency of the plate-type heat exchanger when Al2O3/water mixture nanofluids are used as there are limited studies related to the usage of Al2O3/water mixture nanofluids in the plate-type heat exchanger not only experimental but also numerical methodologies.
      Citation: International Journal of Numerical Methods for Heat & Fluid Flow
      PubDate: 2018-09-14T09:54:33Z
      DOI: 10.1108/HFF-05-2018-0189
       
  • Simulation and experimental analysis of heat transfer characteristics in
           the plate type heat exchangers using TiO2/water nanofluid
    • Abstract: International Journal of Numerical Methods for Heat & Fluid Flow, Ahead of Print.
      Purpose The plate heat exchangers (PHE) with small size but large efficiency are compact types of heat exchangers formed by corrugated thin pressed plates, operating at higher pressures when compared to most other traditional exchangers. This paper aims to analyze heat transfer characteristics in the PHE experimentally and numerically. Design/methodology/approach Computational fluid dynamics analysis has been used to simulate the problem by using the ANSYS fluent 16 software. Also, the effect of using TiO2/water nanofluid as working fluid was investigated. TiO2/water nanofluid had 2% (Wt/Wt) nanoparticle content. To improve solubility of the TiO2 nanoparticles, Triton X-100 was added to the mixture. The results have been achieved in different working condition with changes in fluid flow rate and its temperature. Findings The obtained results showed that using TiO2/water nanofluid improved the overall heat transfer coefficient averagely as 6%, whereas maximum improvement in overall heat transfer coefficient was 10%. Also, theoretical and experimental results are in line with each other. Originality/value The most important feature which separates the present study from the literature is that nanofluid is prepared by using TiO2 nanoparticles in optimum size and mixing ratio with surfactant usage to prevent sedimentation and flocculation problems. This process also prevents particle accumulation that may occur inside the PHE. The main aim of the present study is to predict heat transfer characteristics of nanofluids in a plate heat exchanger. Therefore, it will be possible to analyze thermal performance of the nanofluids without any experiment.
      Citation: International Journal of Numerical Methods for Heat & Fluid Flow
      PubDate: 2018-09-07T10:32:38Z
      DOI: 10.1108/HFF-05-2018-0191
       
  • A cylindrical insert for parabolic trough solar collector
    • Abstract: International Journal of Numerical Methods for Heat & Fluid Flow, Ahead of Print.
      Purpose The purpose of this paper is to investigate a cylindrical flow insert for a parabolic trough solar collector. Centrally placed and eccentric placed inserts are investigated in a systematic way to determine which configuration leads to the maximum thermal enhancement. Design/methodology/approach The analysis is performed in SolidWorks Flow Simulation with a validated computational fluid dynamics model. Moreover, the useful heat production and the pumping work demand increase are evaluated using the exergy and the overall efficiency criteria. The different scenarios are compared for inlet temperature of 600 K, flow rate of 100 L/min and Syltherm 800 as the working fluid. Moreover, the inlet temperature is examined from 450 to 650 K, and the diameter of the insert is investigated up to 50 mm. Findings According to the final results, the use of a cylindrical insert of 30 mm diameter is the most sustainable choice which leads to 0.56 per cent thermal efficiency enhancement. This insert was examined in various eccentric positions, and it is found that the optimum location is 10 mm over the initial position in the vertical direction. The thermal enhancement, in this case, is about 0.69 per cent. The pumping work demand was increased about three times with the insert of 30 mm, but the absolute values of this parameter are too low compared to the useful heat production. So, it is proved that the increase in the pumping work is not able to eliminate the useful heat production increase. Moreover, the thermal enhancement is found to be greater at higher temperature levels and can reach up to 1 per cent for an inlet temperature of r650 K. Originality/value The present work is a systematic investigation of the cylindrical flow insert in a parabolic trough collector. Different diameters of this insert, as well as different positions in two dimensions, are examined using a parametrization of angle-radius. To the authors’ knowledge, there is no other study in the literature that investigates the presented many cases systematically with the followed methodology on parabolic trough collectors. Moreover, the results of this work are evaluated with various criteria (thermal, exergy and overall efficiency), something which is not found in the literature.
      Citation: International Journal of Numerical Methods for Heat & Fluid Flow
      PubDate: 2018-09-04T12:40:18Z
      DOI: 10.1108/HFF-05-2018-0190
       
 
 
JournalTOCs
School of Mathematical and Computer Sciences
Heriot-Watt University
Edinburgh, EH14 4AS, UK
Email: journaltocs@hw.ac.uk
Tel: +00 44 (0)131 4513762
Fax: +00 44 (0)131 4513327
 
Home (Search)
Subjects A-Z
Publishers A-Z
Customise
APIs
Your IP address: 18.212.83.37
 
About JournalTOCs
API
Help
News (blog, publications)
JournalTOCs on Twitter   JournalTOCs on Facebook

JournalTOCs © 2009-