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Publisher: Elsevier   (Total: 3183 journals)

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Showing 1 - 200 of 3183 Journals sorted alphabetically
Academic Pediatrics     Hybrid Journal   (Followers: 38, SJR: 1.655, CiteScore: 2)
Academic Radiology     Hybrid Journal   (Followers: 26, SJR: 1.015, CiteScore: 2)
Accident Analysis & Prevention     Partially Free   (Followers: 102, SJR: 1.462, CiteScore: 3)
Accounting Forum     Hybrid Journal   (Followers: 28, SJR: 0.932, CiteScore: 2)
Accounting, Organizations and Society     Hybrid Journal   (Followers: 40, SJR: 1.771, CiteScore: 3)
Achievements in the Life Sciences     Open Access   (Followers: 7)
Acta Anaesthesiologica Taiwanica     Open Access   (Followers: 6)
Acta Astronautica     Hybrid Journal   (Followers: 436, SJR: 0.758, CiteScore: 2)
Acta Automatica Sinica     Full-text available via subscription   (Followers: 2)
Acta Biomaterialia     Hybrid Journal   (Followers: 28, SJR: 1.967, CiteScore: 7)
Acta Colombiana de Cuidado Intensivo     Full-text available via subscription   (Followers: 3)
Acta de Investigación Psicológica     Open Access   (Followers: 3)
Acta Ecologica Sinica     Open Access   (Followers: 11, SJR: 0.18, CiteScore: 1)
Acta Histochemica     Hybrid Journal   (Followers: 5, SJR: 0.661, CiteScore: 2)
Acta Materialia     Hybrid Journal   (Followers: 312, SJR: 3.263, CiteScore: 6)
Acta Mathematica Scientia     Full-text available via subscription   (Followers: 5, SJR: 0.504, CiteScore: 1)
Acta Mechanica Solida Sinica     Full-text available via subscription   (Followers: 9, SJR: 0.542, CiteScore: 1)
Acta Oecologica     Hybrid Journal   (Followers: 12, SJR: 0.834, CiteScore: 2)
Acta Otorrinolaringologica (English Edition)     Full-text available via subscription  
Acta Otorrinolaringológica Española     Full-text available via subscription   (Followers: 2, SJR: 0.307, CiteScore: 0)
Acta Pharmaceutica Sinica B     Open Access   (Followers: 1, SJR: 1.793, CiteScore: 6)
Acta Poética     Open Access   (Followers: 4, SJR: 0.101, CiteScore: 0)
Acta Psychologica     Hybrid Journal   (Followers: 26, SJR: 1.331, CiteScore: 2)
Acta Sociológica     Open Access   (Followers: 1)
Acta Tropica     Hybrid Journal   (Followers: 6, SJR: 1.052, CiteScore: 2)
Acta Urológica Portuguesa     Open Access  
Actas Dermo-Sifiliograficas     Full-text available via subscription   (Followers: 3, SJR: 0.374, CiteScore: 1)
Actas Dermo-Sifiliográficas (English Edition)     Full-text available via subscription   (Followers: 2)
Actas Urológicas Españolas     Full-text available via subscription   (Followers: 3, SJR: 0.344, CiteScore: 1)
Actas Urológicas Españolas (English Edition)     Full-text available via subscription   (Followers: 1)
Actualites Pharmaceutiques     Full-text available via subscription   (Followers: 7, SJR: 0.19, CiteScore: 0)
Actualites Pharmaceutiques Hospitalieres     Full-text available via subscription   (Followers: 3)
Acupuncture and Related Therapies     Hybrid Journal   (Followers: 8)
Acute Pain     Full-text available via subscription   (Followers: 15, SJR: 2.671, CiteScore: 5)
Ad Hoc Networks     Hybrid Journal   (Followers: 11, SJR: 0.53, CiteScore: 4)
Addictive Behaviors     Hybrid Journal   (Followers: 18, SJR: 1.29, CiteScore: 3)
Addictive Behaviors Reports     Open Access   (Followers: 9, SJR: 0.755, CiteScore: 2)
Additive Manufacturing     Hybrid Journal   (Followers: 11, SJR: 2.611, CiteScore: 8)
Additives for Polymers     Full-text available via subscription   (Followers: 23)
Advanced Drug Delivery Reviews     Hybrid Journal   (Followers: 183, SJR: 4.09, CiteScore: 13)
Advanced Engineering Informatics     Hybrid Journal   (Followers: 12, SJR: 1.167, CiteScore: 4)
Advanced Powder Technology     Hybrid Journal   (Followers: 17, SJR: 0.694, CiteScore: 3)
Advances in Accounting     Hybrid Journal   (Followers: 9, SJR: 0.277, CiteScore: 1)
Advances in Agronomy     Full-text available via subscription   (Followers: 17, SJR: 2.384, CiteScore: 5)
Advances in Anesthesia     Full-text available via subscription   (Followers: 29, SJR: 0.126, CiteScore: 0)
Advances in Antiviral Drug Design     Full-text available via subscription   (Followers: 2)
Advances in Applied Mathematics     Full-text available via subscription   (Followers: 12, SJR: 0.992, CiteScore: 1)
Advances in Applied Mechanics     Full-text available via subscription   (Followers: 12, SJR: 1.551, CiteScore: 4)
Advances in Applied Microbiology     Full-text available via subscription   (Followers: 24, SJR: 2.089, CiteScore: 5)
Advances In Atomic, Molecular, and Optical Physics     Full-text available via subscription   (Followers: 15, SJR: 0.572, CiteScore: 2)
Advances in Biological Regulation     Hybrid Journal   (Followers: 4, SJR: 2.61, CiteScore: 7)
Advances in Botanical Research     Full-text available via subscription   (Followers: 2, SJR: 0.686, CiteScore: 2)
Advances in Cancer Research     Full-text available via subscription   (Followers: 34, SJR: 3.043, CiteScore: 6)
Advances in Carbohydrate Chemistry and Biochemistry     Full-text available via subscription   (Followers: 9, SJR: 1.453, CiteScore: 2)
Advances in Catalysis     Full-text available via subscription   (Followers: 5, SJR: 1.992, CiteScore: 5)
Advances in Cell Aging and Gerontology     Full-text available via subscription   (Followers: 5)
Advances in Cellular and Molecular Biology of Membranes and Organelles     Full-text available via subscription   (Followers: 14)
Advances in Chemical Engineering     Full-text available via subscription   (Followers: 29, SJR: 0.156, CiteScore: 1)
Advances in Child Development and Behavior     Full-text available via subscription   (Followers: 11, SJR: 0.713, CiteScore: 1)
Advances in Chronic Kidney Disease     Full-text available via subscription   (Followers: 10, SJR: 1.316, CiteScore: 2)
Advances in Clinical Chemistry     Full-text available via subscription   (Followers: 26, SJR: 1.562, CiteScore: 3)
Advances in Colloid and Interface Science     Full-text available via subscription   (Followers: 20, SJR: 1.977, CiteScore: 8)
Advances in Computers     Full-text available via subscription   (Followers: 14, SJR: 0.205, CiteScore: 1)
Advances in Dermatology     Full-text available via subscription   (Followers: 15)
Advances in Developmental Biology     Full-text available via subscription   (Followers: 13)
Advances in Digestive Medicine     Open Access   (Followers: 12)
Advances in DNA Sequence-Specific Agents     Full-text available via subscription   (Followers: 7)
Advances in Drug Research     Full-text available via subscription   (Followers: 26)
Advances in Ecological Research     Full-text available via subscription   (Followers: 43, SJR: 2.524, CiteScore: 4)
Advances in Engineering Software     Hybrid Journal   (Followers: 29, SJR: 1.159, CiteScore: 4)
Advances in Experimental Biology     Full-text available via subscription   (Followers: 8)
Advances in Experimental Social Psychology     Full-text available via subscription   (Followers: 51, SJR: 5.39, CiteScore: 8)
Advances in Exploration Geophysics     Full-text available via subscription   (Followers: 1)
Advances in Fluorine Science     Full-text available via subscription   (Followers: 9)
Advances in Food and Nutrition Research     Full-text available via subscription   (Followers: 65, SJR: 0.591, CiteScore: 2)
Advances in Fuel Cells     Full-text available via subscription   (Followers: 17)
Advances in Genetics     Full-text available via subscription   (Followers: 21, SJR: 1.354, CiteScore: 4)
Advances in Genome Biology     Full-text available via subscription   (Followers: 10, SJR: 12.74, CiteScore: 13)
Advances in Geophysics     Full-text available via subscription   (Followers: 7, SJR: 1.193, CiteScore: 3)
Advances in Heat Transfer     Full-text available via subscription   (Followers: 26, SJR: 0.368, CiteScore: 1)
Advances in Heterocyclic Chemistry     Full-text available via subscription   (Followers: 11, SJR: 0.749, CiteScore: 3)
Advances in Human Factors/Ergonomics     Full-text available via subscription   (Followers: 25)
Advances in Imaging and Electron Physics     Full-text available via subscription   (Followers: 3, SJR: 0.193, CiteScore: 0)
Advances in Immunology     Full-text available via subscription   (Followers: 37, SJR: 4.433, CiteScore: 6)
Advances in Inorganic Chemistry     Full-text available via subscription   (Followers: 10, SJR: 1.163, CiteScore: 2)
Advances in Insect Physiology     Full-text available via subscription   (Followers: 2, SJR: 1.938, CiteScore: 3)
Advances in Integrative Medicine     Hybrid Journal   (Followers: 6, SJR: 0.176, CiteScore: 0)
Advances in Intl. Accounting     Full-text available via subscription   (Followers: 3)
Advances in Life Course Research     Hybrid Journal   (Followers: 9, SJR: 0.682, CiteScore: 2)
Advances in Lipobiology     Full-text available via subscription   (Followers: 1)
Advances in Magnetic and Optical Resonance     Full-text available via subscription   (Followers: 8)
Advances in Marine Biology     Full-text available via subscription   (Followers: 21, SJR: 0.88, CiteScore: 2)
Advances in Mathematics     Full-text available via subscription   (Followers: 14, SJR: 3.027, CiteScore: 2)
Advances in Medical Sciences     Hybrid Journal   (Followers: 8, SJR: 0.694, CiteScore: 2)
Advances in Medicinal Chemistry     Full-text available via subscription   (Followers: 6)
Advances in Microbial Physiology     Full-text available via subscription   (Followers: 5, SJR: 1.158, CiteScore: 3)
Advances in Molecular and Cell Biology     Full-text available via subscription   (Followers: 24)
Advances in Molecular and Cellular Endocrinology     Full-text available via subscription   (Followers: 8)
Advances in Molecular Toxicology     Full-text available via subscription   (Followers: 7, SJR: 0.182, CiteScore: 0)
Advances in Nanoporous Materials     Full-text available via subscription   (Followers: 5)
Advances in Oncobiology     Full-text available via subscription   (Followers: 2)
Advances in Organ Biology     Full-text available via subscription   (Followers: 2)
Advances in Organometallic Chemistry     Full-text available via subscription   (Followers: 18, SJR: 1.875, CiteScore: 4)
Advances in Parallel Computing     Full-text available via subscription   (Followers: 7, SJR: 0.174, CiteScore: 0)
Advances in Parasitology     Full-text available via subscription   (Followers: 5, SJR: 1.579, CiteScore: 4)
Advances in Pediatrics     Full-text available via subscription   (Followers: 27, SJR: 0.461, CiteScore: 1)
Advances in Pharmaceutical Sciences     Full-text available via subscription   (Followers: 19)
Advances in Pharmacology     Full-text available via subscription   (Followers: 17, SJR: 1.536, CiteScore: 3)
Advances in Physical Organic Chemistry     Full-text available via subscription   (Followers: 9, SJR: 0.574, CiteScore: 1)
Advances in Phytomedicine     Full-text available via subscription  
Advances in Planar Lipid Bilayers and Liposomes     Full-text available via subscription   (Followers: 3, SJR: 0.109, CiteScore: 1)
Advances in Plant Biochemistry and Molecular Biology     Full-text available via subscription   (Followers: 10)
Advances in Plant Pathology     Full-text available via subscription   (Followers: 6)
Advances in Porous Media     Full-text available via subscription   (Followers: 5)
Advances in Protein Chemistry     Full-text available via subscription   (Followers: 19)
Advances in Protein Chemistry and Structural Biology     Full-text available via subscription   (Followers: 20, SJR: 0.791, CiteScore: 2)
Advances in Psychology     Full-text available via subscription   (Followers: 67)
Advances in Quantum Chemistry     Full-text available via subscription   (Followers: 6, SJR: 0.371, CiteScore: 1)
Advances in Radiation Oncology     Open Access   (Followers: 1, SJR: 0.263, CiteScore: 1)
Advances in Small Animal Medicine and Surgery     Hybrid Journal   (Followers: 3, SJR: 0.101, CiteScore: 0)
Advances in Space Biology and Medicine     Full-text available via subscription   (Followers: 6)
Advances in Space Research     Full-text available via subscription   (Followers: 421, SJR: 0.569, CiteScore: 2)
Advances in Structural Biology     Full-text available via subscription   (Followers: 5)
Advances in Surgery     Full-text available via subscription   (Followers: 13, SJR: 0.555, CiteScore: 2)
Advances in the Study of Behavior     Full-text available via subscription   (Followers: 37, SJR: 2.208, CiteScore: 4)
Advances in Veterinary Medicine     Full-text available via subscription   (Followers: 20)
Advances in Veterinary Science and Comparative Medicine     Full-text available via subscription   (Followers: 15)
Advances in Virus Research     Full-text available via subscription   (Followers: 6, SJR: 2.262, CiteScore: 5)
Advances in Water Resources     Hybrid Journal   (Followers: 53, SJR: 1.551, CiteScore: 3)
Aeolian Research     Hybrid Journal   (Followers: 6, SJR: 1.117, CiteScore: 3)
Aerospace Science and Technology     Hybrid Journal   (Followers: 384, SJR: 0.796, CiteScore: 3)
AEU - Intl. J. of Electronics and Communications     Hybrid Journal   (Followers: 8, SJR: 0.42, CiteScore: 2)
African J. of Emergency Medicine     Open Access   (Followers: 6, SJR: 0.296, CiteScore: 0)
Ageing Research Reviews     Hybrid Journal   (Followers: 12, SJR: 3.671, CiteScore: 9)
Aggression and Violent Behavior     Hybrid Journal   (Followers: 475, SJR: 1.238, CiteScore: 3)
Agri Gene     Hybrid Journal   (Followers: 1, SJR: 0.13, CiteScore: 0)
Agricultural and Forest Meteorology     Hybrid Journal   (Followers: 18, SJR: 1.818, CiteScore: 5)
Agricultural Systems     Hybrid Journal   (Followers: 31, SJR: 1.156, CiteScore: 4)
Agricultural Water Management     Hybrid Journal   (Followers: 44, SJR: 1.272, CiteScore: 3)
Agriculture and Agricultural Science Procedia     Open Access   (Followers: 4)
Agriculture and Natural Resources     Open Access   (Followers: 3)
Agriculture, Ecosystems & Environment     Hybrid Journal   (Followers: 58, SJR: 1.747, CiteScore: 4)
Ain Shams Engineering J.     Open Access   (Followers: 5, SJR: 0.589, CiteScore: 3)
Air Medical J.     Hybrid Journal   (Followers: 8, SJR: 0.26, CiteScore: 0)
AKCE Intl. J. of Graphs and Combinatorics     Open Access   (SJR: 0.19, CiteScore: 0)
Alcohol     Hybrid Journal   (Followers: 12, SJR: 1.153, CiteScore: 3)
Alcoholism and Drug Addiction     Open Access   (Followers: 12)
Alergologia Polska : Polish J. of Allergology     Full-text available via subscription   (Followers: 1)
Alexandria Engineering J.     Open Access   (Followers: 2, SJR: 0.604, CiteScore: 3)
Alexandria J. of Medicine     Open Access   (Followers: 1, SJR: 0.191, CiteScore: 1)
Algal Research     Partially Free   (Followers: 11, SJR: 1.142, CiteScore: 4)
Alkaloids: Chemical and Biological Perspectives     Full-text available via subscription   (Followers: 2)
Allergologia et Immunopathologia     Full-text available via subscription   (Followers: 1, SJR: 0.504, CiteScore: 1)
Allergology Intl.     Open Access   (Followers: 5, SJR: 1.148, CiteScore: 2)
Alpha Omegan     Full-text available via subscription   (SJR: 3.521, CiteScore: 6)
ALTER - European J. of Disability Research / Revue Européenne de Recherche sur le Handicap     Full-text available via subscription   (Followers: 10, SJR: 0.201, CiteScore: 1)
Alzheimer's & Dementia     Hybrid Journal   (Followers: 53, SJR: 4.66, CiteScore: 10)
Alzheimer's & Dementia: Diagnosis, Assessment & Disease Monitoring     Open Access   (Followers: 6, SJR: 1.796, CiteScore: 4)
Alzheimer's & Dementia: Translational Research & Clinical Interventions     Open Access   (Followers: 6, SJR: 1.108, CiteScore: 3)
Ambulatory Pediatrics     Hybrid Journal   (Followers: 5)
American Heart J.     Hybrid Journal   (Followers: 58, SJR: 3.267, CiteScore: 4)
American J. of Cardiology     Hybrid Journal   (Followers: 63, SJR: 1.93, CiteScore: 3)
American J. of Emergency Medicine     Hybrid Journal   (Followers: 46, SJR: 0.604, CiteScore: 1)
American J. of Geriatric Pharmacotherapy     Full-text available via subscription   (Followers: 12)
American J. of Geriatric Psychiatry     Hybrid Journal   (Followers: 14, SJR: 1.524, CiteScore: 3)
American J. of Human Genetics     Hybrid Journal   (Followers: 37, SJR: 7.45, CiteScore: 8)
American J. of Infection Control     Hybrid Journal   (Followers: 29, SJR: 1.062, CiteScore: 2)
American J. of Kidney Diseases     Hybrid Journal   (Followers: 36, SJR: 2.973, CiteScore: 4)
American J. of Medicine     Hybrid Journal   (Followers: 50)
American J. of Medicine Supplements     Full-text available via subscription   (Followers: 3, SJR: 1.967, CiteScore: 2)
American J. of Obstetrics and Gynecology     Hybrid Journal   (Followers: 255, SJR: 2.7, CiteScore: 4)
American J. of Ophthalmology     Hybrid Journal   (Followers: 66, SJR: 3.184, CiteScore: 4)
American J. of Ophthalmology Case Reports     Open Access   (Followers: 5, SJR: 0.265, CiteScore: 0)
American J. of Orthodontics and Dentofacial Orthopedics     Full-text available via subscription   (Followers: 6, SJR: 1.289, CiteScore: 1)
American J. of Otolaryngology     Hybrid Journal   (Followers: 25, SJR: 0.59, CiteScore: 1)
American J. of Pathology     Hybrid Journal   (Followers: 32, SJR: 2.139, CiteScore: 4)
American J. of Preventive Medicine     Hybrid Journal   (Followers: 28, SJR: 2.164, CiteScore: 4)
American J. of Surgery     Hybrid Journal   (Followers: 39, SJR: 1.141, CiteScore: 2)
American J. of the Medical Sciences     Hybrid Journal   (Followers: 12, SJR: 0.767, CiteScore: 1)
Ampersand : An Intl. J. of General and Applied Linguistics     Open Access   (Followers: 7)
Anaerobe     Hybrid Journal   (Followers: 4, SJR: 1.144, CiteScore: 3)
Anaesthesia & Intensive Care Medicine     Full-text available via subscription   (Followers: 66, SJR: 0.138, CiteScore: 0)
Anaesthesia Critical Care & Pain Medicine     Full-text available via subscription   (Followers: 24, SJR: 0.411, CiteScore: 1)
Anales de Cirugia Vascular     Full-text available via subscription   (Followers: 1)
Anales de Pediatría     Full-text available via subscription   (Followers: 3, SJR: 0.277, CiteScore: 0)
Anales de Pediatría (English Edition)     Full-text available via subscription  
Anales de Pediatría Continuada     Full-text available via subscription  
Analytic Methods in Accident Research     Hybrid Journal   (Followers: 5, SJR: 4.849, CiteScore: 10)
Analytica Chimica Acta     Hybrid Journal   (Followers: 44, SJR: 1.512, CiteScore: 5)
Analytica Chimica Acta : X     Open Access  
Analytical Biochemistry     Hybrid Journal   (Followers: 209, SJR: 0.633, CiteScore: 2)
Analytical Chemistry Research     Open Access   (Followers: 13, SJR: 0.411, CiteScore: 2)
Analytical Spectroscopy Library     Full-text available via subscription   (Followers: 14)
Anesthésie & Réanimation     Full-text available via subscription   (Followers: 2)
Anesthesiology Clinics     Full-text available via subscription   (Followers: 25, SJR: 0.683, CiteScore: 2)
Angiología     Full-text available via subscription   (SJR: 0.121, CiteScore: 0)
Angiologia e Cirurgia Vascular     Open Access   (Followers: 1, SJR: 0.111, CiteScore: 0)
Animal Behaviour     Hybrid Journal   (Followers: 223, SJR: 1.58, CiteScore: 3)
Animal Feed Science and Technology     Hybrid Journal   (Followers: 6, SJR: 0.937, CiteScore: 2)
Animal Reproduction Science     Hybrid Journal   (Followers: 7, SJR: 0.704, CiteScore: 2)

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Similar Journals
Journal Cover
International Journal of Thermal Sciences
Journal Prestige (SJR): 1.429
Citation Impact (citeScore): 4
Number of Followers: 20  
 
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 1290-0729
Published by Elsevier Homepage  [3183 journals]
  • Multistage cooling and freezing of a saline spherical water droplet
    • Abstract: Publication date: Available online 11 October 2019Source: International Journal of Thermal SciencesAuthor(s): A.R. Dehghani-Sanij, S. MacLachlan, G.F. Naterer, Y.S. Muzychka, R.D. Haynes, V. Enjilela In this paper, the thermal behaviour of a saline water droplet during flight over a marine vessel in cold weather conditions is investigated by analytical and semi-analytical techniques. To predict and analyze the droplet cooling and freezing processes, three stages are employed: a liquid cooling stage, a solidification stage, and a solid cooling stage. The theoretical model considers heat transfer via conduction inside the droplet as well as convection, evaporation (just for the liquid cooling stage), and radiation heat transfer from the droplet's surface to the ambient air. A novel semi-analytical solution technique is developed to analyze the inward moving boundary problem for the solidification stage. The results show that the liquid cooling stage is very short, and the temperature at the droplet's center remains close to the initial droplet temperature. During the solidification stage, the velocity of the inward freezing front within the droplet is approximately constant, and the temperature variations are linear when the temperature inside the droplet reaches the freezing temperature. The solid cooling stage is much longer than the other stages, and the temperature changes are non-linear. For a case study, theoretical predictions show that the average temperature of a droplet with a diameter of 1 mm at the moment of impact on the deck is approximately −1.95°C. Moreover, there is an ice shell with a thickness of 0.06 mm on the surface of the water droplet at the moment of impact.
       
  • Heat transfer enhancement in cryogenic quenching process
    • Abstract: Publication date: January 2020Source: International Journal of Thermal Sciences, Volume 147Author(s): J.N. Chung, S.R. Darr, Jun Dong, Hao Wang, J.W. Hartwig This paper reports a heat transfer advancement in the cryogenic quenching process. An experiment was performed to evaluate the enhancement of quenching heat transfer by the use of metal tubes with low thermal conductivity coating layers. Four coating thicknesses with various coolant mass flow rates of liquid nitrogen were investigated. The results indicated that the tube inner surface coating greatly enhanced the quenching efficiency. The quenching efficiency was found to increase with increasing number of coating layers, and the efficiency also increased with decreasing mass flow rates. In general, the efficiencies cover a range between 40.6% and 80%. Comparing to the bare surface case, the percentage increase in the quenching efficiency was the minimum at 4.2% for a single coated layer at the highest flow rate and the maximum of 109.1% for four coated layers at the lowest flow rate. The coated tubes could save up to 53% in the amount of cryogen consumption.
       
  • Thermal management and structural parameters optimization of MCM-BGA 3D
           package model
    • Abstract: Publication date: January 2020Source: International Journal of Thermal Sciences, Volume 147Author(s): Liang Gong, Yu-Peng Xu, Bin Ding, Zhi-Hao Zhang, Zhao-Qin Huang The multi-core technology promotes the efficiency improvement of microelectronic devices. However, the increasing power and heat flux lead to heat dissipation problems on hotspots, which severely affects the performance of electronic devices and impedes the development of electronic techniques. Therefore, thermal management suitable for electronic packaging is crucial. In this paper, a multi-chips module combined with ball grid array (MCM-BGA) 3D package model was established; the thermal interface resistance between the micro-channel heat sink and heat spreader was considered; the flow heat transfer as well as thermal stress performance of the model were discussed. The results indicate that the MCM-BGA 3D package model can maintain the maximum temperature and thermal stress in a satisfactory range. However, the major concentration areas of the maximum temperature are the chips and solder balls, especially the welding spots. Based on the analysis, the multi-parameters optimization of structural parameters was conducted. After the optimization, the maximum temperature and thermal stress decrease by 5 K and 20% in average, respectively. The optimal thickness of thermal interface material, heat spreader and substrate are 0.1 mm, 1.2 mm and 1.2 mm, respectively.
       
  • Investigation of flow boiling heat transfer and pressure drop of R134a in
           a rectangular channel with wavy fin
    • Abstract: Publication date: January 2020Source: International Journal of Thermal Sciences, Volume 147Author(s): M. Amaranatha Raju, T.P. Ashok Babu, C. Ranganayakulu The saturated flow boiling heat transfer and pressure drop studies of R134a were experimentally investigated in a rectangular channel with wavy fin. Experiments were performed at mass flux range 30–50 kg m−2 s−1, heat flux range 11–18 kW m−2 and quality 0.26–0.8. The experimental data were obtained in a brazed test section. In preliminary step, single phase experiments were conducted to find out the j and f data of the wavy fin. In second step, two-phase flow boiling experiments were conducted to estimate the heat transfer and frictional coefficient based on experimental data. The trends of heat transfer and pressure drop with respect to mass flux, heat flux and quality were studied. Two-phase local boiling heat transfer coefficient is correlated in terms of Reynolds number factor F, and Martinelli parameter X. Pressure drop is correlated in terms of two-phase frictional multiplier, ϕf and Martinelli parameter, X.
       
  • A novel method and parameters for evaluating thermal sensation of textile
    • Abstract: Publication date: Available online 4 October 2019Source: International Journal of Thermal SciencesAuthor(s): Lexi Tu, Hua Shen, Fumei Wang In this study, a novel method simulating the heat transmission between the human skin, textile and environment was developed to evaluate the initial thermal sensation when the human skin touched textile products. Two sets of predictive parameters were proposed based on the heat flux curves to separately represent the initial cool and warm thermal responses perceived by skin at the initial contacting time. A subjective test was also carried out in a climate chamber where the temperature was fixed at 20 ± 2 °C and the relative humidity was maintained at 65 ± 4%. In addition, series of numerical studies was utilized to study the effects of pretreated environment on these parameters. The validity of the proposed method and parameters was then confirmed by a comparison of the objective measurement and subjective evaluation. The results suggested that the transient maximum heat flux Qmax, the maximum heat flux rising rate K and the heat energy W were strongly related to the thermal sensation of subjects. Besides, the drastic cool feeling time t was supposed to be a value reflecting the rate and duration of such feeling. Then, the K was found to be a parameter not only related to the thermal properties, but also closely associated with the surface morphology of the samples. The relative humidity was a dominant factor affecting the thermal sensation, especially for textile products with a high moisture regain. The cool feeling was observed to increase with the higher relative humidity, as the heat capacity and thermal conductivity increased when more moisture was absorbed.
       
  • Numerical study of slug flow heat transfer in microchannels
    • Abstract: Publication date: January 2020Source: International Journal of Thermal Sciences, Volume 147Author(s): Morteza Bayareh, Mohsen Nasr Esfahany, Nader Afshar, Mohsen Bastegani In the present paper, the heat transfer of slug flow in rectangular microchannels is studied numerically. The Al2O3-water nanofluid with the volume fraction of 1% is used as a homogeneous liquid. Three different configurations are considered to investigate the hydrodynamics and heat transfer in the microchannels. Boundary mesh adaptation method is used to capture the liquid film around gas bubbles. Slug flow characteristics are simulated with a very low computational time compared to previous researches. Slug and bubble lengths, liquid film properties, pressure drop, gas void fraction and heat transfer characteristics are studied. Results show that different inlet configurations impact on slug and bubble lengths. Gas hold-up is influenced by vortices and high frequency fluctuations that are created in the liquid film due to the difference between gas and slug acceleration. It is found that the Nusselt number is an increasing function of slug length and unit cell length. The results reveal that the hottest point on the wall is where the back tail vortex is generated. The nanofluid enhances the heat transfer coefficient by 10% in comparison with the pure water.
       
  • Effect of backward facing step shape on 3D mixed convection of Bingham
           fluid
    • Abstract: Publication date: January 2020Source: International Journal of Thermal Sciences, Volume 147Author(s): Fetta Danane, Ahlem Boudiaf, Omar Mahfoud, Seif-Eddine Ouyahia, Nabila Labsi, Youb Khaled Benkahla The present paper examines the viscous laminar mixed convection flow of a Bingham viscoplastic fluid in order to enhance the thermal performance and thus reduce the pressure drop. To achieve this, three-dimensional numerical simulations for vertical, inclined, and round backward facing step inside a horizontal rectangular duct are established.The effects of variation in buoyancy, viscous and inertia forces variations as well as the step shape, on thermal and hydrodynamic behaviours of the fluid are investigated. The structure of the flow is significantly influenced by the variation of Bingham and Richardson numbers and the backward facing steps shape. It is found that the recirculation zones, which are the main source of thermal and hydrodynamic losses, are intensified with the increase in buoyancy forces represented by the Richardson number. Moreover, the recirculation zones are attenuated as the viscous forces predominate. It is also noticed that the recirculation zones decrease or disappear as the geometry is modified by reducing the angle or the shape of the step. The change of the step shape reduces significantly the pressure drops of about 11.77% and 58.83% for the inclined and rounded backward facing steps; respectively, compared to the vertical backward facing step. However, the pressure coefficient decreases along the duct and increases in presence of a recirculation zone. Also, the highest value of the total Nusselt number is obtained for a round backward facing step in mixed convection. Otherwise, an increase in the Bingham number extends the plug structure in the three geometries.
       
  • Unifying boiling and degassing theories: Self-similar and pseudo-steady
           state analysis
    • Abstract: Publication date: December 2019Source: International Journal of Thermal Sciences, Volume 146Author(s): M. Kostoglou, T.D. Karapantsios The two phenomena of degassing and boiling, regarding bubble growth in a liquid with a dissolved gas, are studied separately in literature with the corresponding theories to diverge from each other at the boiling temperature. Here a unifying approach is developed in terms of heat and mass transfer conservation laws to describe both phenomena. It is shown that the corresponding system of partial differential equations admits a self-similar solution for constant bubble growth rate conditions. The self-similarity solution is further simplified in order to indicate several asymptotic bubble growth regimes. The case of non-constant bubble growth rate conditions is treated only for the asymptotic regime of quasi-steady growth. Several results for idealized and realistic bubble growth cases are presented. It is shown that the two individual theories of degassing and boiling are unified through the appropriate manipulation of the bubble temperature. Small temperature differences can yield large variation in bubble growth rate in a small range around the boiling temperature. The system water-nitrogen is examined in detail and it is found to be outside of the domain of asymptotic theories (i.e. the complete self-similar solution has to be employed).Graphical abstractTheory of bubble growth in a liquid with dissolved gas. Unifying degassing and boiling approaches.Image 1
       
  • Effect of horizontal spacing and tilt angle on thermo-buoyant natural
           convection from two horizontally aligned square cylinders
    • Abstract: Publication date: December 2019Source: International Journal of Thermal Sciences, Volume 146Author(s): Subhasisa Rath, Sukanta Kumar Dash Laminar natural convection heat transfer from two horizontally aligned square cylinders has been investigated numerically using a finite-volume method (FVM). Computations were performed to delineate the momentum and heat transfer characteristics under the following ranges of parameters: horizontal spacing between the cylinders (0 ≤ S/W ≤ 10), tilt angle of the square cylinder (00≤δ ≤ 600), and Grashof number (10 ≤ Gr ≤ 105) for some specific Newtonian fluids having Prandtl number (0.71 ≤ Pr ≤ 7). Computed results are presented in terms of temperature contours and streamlines, velocity and temperature profiles, the mass flow rate in the passage between the cylinders, local and average Nu, and the drag coefficient. The average Nu increases with decrease in the horizontal spacing up to a certain limit, whereas it significantly degrades with a further decrease in the spacing. The square cylinder having δ = 450 shows a higher heat transfer, whereas it is least for δ = 00. At higher Gr and Pr, the average Nu is found to be in excess of 22% at δ = 450 compared to at δ = 00. Overall, the average Nu has a strong dependence on both Gr and Pr, whereas it is a weak function of S/W and δ. Furthermore, the total drag coefficient (Cd) shows an adverse dependence on both Gr and Pr. The flow resistance is higher at the optimum horizontal spacing and decreases significantly with decrease in the spacing. The Cd is found to be lower for δ = 450 and in excess of 30% at δ = 00. Finally, a correlation for the average Nu has been developed, which can be useful for some engineering calculations.
       
  • Performance optimiation of a cylindrical mini-channel heat sink using
           hybrid straight–wavy channel
    • Abstract: Publication date: December 2019Source: International Journal of Thermal Sciences, Volume 146Author(s): Ammar Abdulhaleem Abdulqadur, Hayder Mohammad Jaffal, Dhamyaa Saad Khudhur The problem of high pressure drop remains a challenge in the design of heat sinks using the passive techniques of heat transfer enhancement. Wavy channels are widely used to improve the transfer of a mini-channel heat sink but with an undesirable pressure drop. A new channel design was proposed to enhance the performance of a cylindrical mini-channel heat sink (CMCHS) with a minimal possible pressure drop. The design was a straight–wavy hybrid channel, in which the channel path changes from straight at the entrance of the CMCHS to wavy. 3D computational fluid dynamics was performed to analye the fluid flow and heat transfer of the CMCHS. Simulation was conducted on the CMCHS water with a Reynolds number of less than 500. On the basis of entropy generation minimiation technique, CMCHS performance was optimied using different geometric parameters. The parameters included entrance channel length ratio and the wave amplitude ratios of the second and third sections of the channel. A test rig was manufactured to test CMCHSs for a wide range of operating conditions to validate the simulation model. Two models of CMCHS with straight and hybrid straight–wavy channels were developed on the basis of the optimum dimensions acquired from the numerical prediction. Results revealed that the overall performance of the CMCHS with a straight–wavy channel is better than that with a straight channel under the same operating conditions. The straight–wavy channel is more effective than the conventional straight channel in reducing the maximum surface temperature along the channel length of the CMCHS. The temperature uniformity along the CMCHS with a straight–wavy channel is better than that with a straight channel.
       
  • Lattice Boltzmann simulation of thermal flows with complex geometry using
           a single-node curved boundary condition
    • Abstract: Publication date: December 2019Source: International Journal of Thermal Sciences, Volume 146Author(s): Shi Tao, Baiman Chen, Hanmin Xiao, Simin Huang Thermal curved boundary condition is proposed for lattice Boltzmann simulation of thermal flows with complex geometry. In this scheme, the unknown temperature distribution function at the boundary point is interpolated by the distribution functions at the interface and a further fluid point. The former one is decomposed into the equilibrium and non-equilibrium parts. The equilibrium part can be determined by the boundary conditions, while the anti-bounce back rule is applied to obtain the non-equilibrium part, i.e., the key point for the present scheme. On the other hand, the latter one streams directly from the boundary point. Since information of a single fluid point is needed, the computation involved in the present scheme is completely localized. Another advantage of the method is for the second-order convergence rate in simulations, preserving the overall accuracy of the lattice Boltzmann method. Four thermal problems are used to validate the present scheme. The first two cases, i.e., thermal Couette flow with wall injection, and natural convection in a square cavity are performed to verify the second-order accuracy. It is further applied to the other three thermal flows with complex geometries, including the natural convections in a cavity with a cylinder and in a concentric annulus, and a hot cylinder moving in a channel. Good agreement can be found between the present results and those available in the literature. The five test cases together demonstrate that the present method retains the property of local computation and second-order accuracy simultaneously in the simulations.
       
  • Infrared emissivity characterization of carbon nanotubes dispersed
           poly(ethylene terephthalate) fibers
    • Abstract: Publication date: December 2019Source: International Journal of Thermal Sciences, Volume 146Author(s): M.C. Larciprete, S. Paoloni, N. Orazi, F. Mercuri, M. Orth, Y. Gloy, M. Centini, R. Li Voti, C. Sibilia The infrared (IR) emissivity of a set of polymeric fibers composed of randomly oriented carbon nanotubes dispersed into a poly(ethylene terephthalate) matrix host was investigated. Samples containing different amounts of carbon nanotubes in the range between 1 and 10 wt% were analyzed. The effects of the included carbon nanotubes on electrical and morphological properties were studied by means of electric conductance, scanning electron micrography and white light interferometry investigations, respectively. The emissivity was characterized in the 3.5–5.1 μm spectral range by using the infrared thermography technique under heating regime. To analyze the obtained results, a theoretical model based on the Maxwell Garnett theory has been proposed. A percolation effect in the electrical conductance and a gradual increase of the emissivity has been observed, respectively with increasing carbon nanotubes content. In particular, morphological investigations showed the emerging surface roughness when carbon nanotubes are added to the polymeric matrix which may further contribute to the increase of the emissivity value. On the basis of the obtained results, it can be concluded that the investigated composite fibers have the potential to develop new materials enabling both high IR emission and large electrical conduction.
       
  • Integral transform method solution for heat transfer in polymer melt flow
           in a parallel plate single screw channel with periodic inlet temperature
    • Abstract: Publication date: December 2019Source: International Journal of Thermal Sciences, Volume 146Author(s): L.X. Bu, Y. Agbessi, J. Biglione, Y. Béreaux, J.-Y. Charmeau This work investigates the capacity of a particular class of flows, namely drag and pressure driven flows, to propagate and distorts a transient sinusoidal temperature disturbance occurring at the inlet of the metering zone of a polymer processing screw channel. The integral transform method is applied to the forced convection heat transfer problem in a parallel plate channel with a general drag and pressure driven flow velocity profile for a Newtonian fluid, with the pressure gradient as an adjustable flow parameter. We follow closely the procedure outlined by Cotta and Özişik in their seminal paper [5]. We found that the knowledge of the lowest eigenvalue in the solution is sufficient to characterise the dampening efficiency of an inlet temperature fluctuation by the flow and that a higher level of positive pressure difference is indeed improving the thermal homogeneity in the flow. Moreover, we found that for any given flow, the higher frequency disturbances are dispersed more efficiently than the lower frequency disturbances.
       
  • Gas-driven thin liquid films: Effect of interfacial shear on the film
           waviness and convective heat transfer
    • Abstract: Publication date: December 2019Source: International Journal of Thermal Sciences, Volume 146Author(s): Mete Budakli, Tatiana Gambaryan-Roisman, Peter Stephan This study is aimed at experimental investigation of hydrodynamics and convective heat transfer in gravity and gas-driven thin liquid wall films. The liquid film has been annularly applied on a vertically aligned heated tube mounted in a flow channel. In the arranged two-phase flow domain, both the liquid film flow and co-current air flow were thermally and hydrodynamically developing. The Reynolds numbers of liquid and gas flows have been varied between 80−800 and 104−105, respectively. The wall heat flux was kept constant at 15W/cm2. In order to elucidate the effect of the film waviness on the convective heat transfer between the heated wall and the liquid film, the wave frequencies and standard deviations of film thickness have been evaluated by applying high-speed shadowgraphy technique. The wall temperature distribution in streamwise direction has been measured. The experimentally obtained average Nusselt numbers have been compared with the wave frequencies and standard deviations of film thickness. Up to a gas Reynolds number of 4⋅104 and for liquid Reynolds numbers between 80 and 800, the convective heat transfer preliminary depends on the liquid Reynolds number rather than the Reynolds number of the gas flow. For this range, the average Nusselt numbers from the gas-driven film experiments are close to those for falling film flows. At the gas Reynolds numbers starting from 7⋅104, significant heat transfer enhancement with the gas flow has been registered over the full range of liquid Reynolds number.
       
  • Atomistic insights into the effects of hydrogen bonds on the melting
           process and heat conduction of erythritol as a promising latent heat
           storage material
    • Abstract: Publication date: December 2019Source: International Journal of Thermal Sciences, Volume 146Author(s): Biao Feng, Li-Wu Fan, Yi Zeng, Jing-Yu Ding, Xue-Feng Shao Molecular dynamics (MD) simulations were performed to give insights into the effects of hydrogen bonds (HBs) on the melting process and heat conduction of erythritol as a promising latent heat storage material. First, among four force fields (GAFF, GROMOS, OPLS and CHARMM), the applicability of GROMOS force field was verified by comparing the predicted density and heat capacity of erythritol at various temperatures of interest with the measured values. The microscopic melting process of erythritol was simulated using the interface/NPT method, leading to a predicted melting point of ~394 K that agrees well with the measured value (~392 K). It was demonstrated that the variation of HBs energy associated with changes of molecular structure is the primary contribution to the latent heat. Upon melting, the strong inter-molecular HBs in solid erythritol break off and form weaker intra- and inter-molecular HBs in the liquid phase. In addition, non-equilibrium MD simulations were performed to study the microscopic heat conduction in erythritol molecules and to examine the dependence of the van der Waals (vdW) and Coulomb heat currents on the interatomic distance. It was revealed that the heat transfer capability of HB interactions is better than those of the Coulomb or vdW interactions. In the solid phase, the amount of heat transfer through HBs becomes greater with increasing the number of HBs. The results shed light on a promising approach to improving the latent heat storage capacity and thermal conductivity of erythritol (and other sugar alcohols) by manipulating the number and strength of HBs.
       
  • Effects on thermal performance enhancement of pin-fin structures for
           insulated gate bipolar transistor (IGBT) cooling in high voltage heater
           system
    • Abstract: Publication date: December 2019Source: International Journal of Thermal Sciences, Volume 146Author(s): Fei Dong, YaKang Feng, ZhiMing Wang, Jie Ni The thermal performance enhancement of pin-fin structures for IGBT cooling in high voltage heater (HVH) system is numerically investigated and experimentally verified in this study. The results revealed that there may be a risk of thermal failure of the IGBT in existing HVH systems. Additionally, a new heat exchanger was designed with pin-fin structures to enhance heat transfer for cooling the IGBT component. To analyze the influence of pin-fin parameters on the cooling effect, a L16(4̂5) orthogonal array was selected to identify the main and secondary parameters, then the optimal combination scheme was found. The sensitivity analysis result showed that the diameter of the pin-fin had the greatest influence on the amount of heat transfer, and the height of pin-fin is the second. For cooling uniformity, height is the most important parameter and the diameter is the second. The optimization scheme obtained by orthogonal design could simultaneously meet the requirements of heat transfer and cooling uniformity. Compared with the original model, the maximum temperature and the maximum difference of the average temperatures of the IGBT chip layer decreased 9.4% and 14.6%, respectively.
       
  • Influence of surface tension on the molten pool morphology in laser
           melting
    • Abstract: Publication date: December 2019Source: International Journal of Thermal Sciences, Volume 146Author(s): Shibai Liu, Jichang Liu, Jinxuan Chen, Xudong Liu The surface tension plays an important role in the distribution and evolution of molten pool morphology during laser melting. In this paper, based on the theory of Smoothed Particles Hydrodynamics (SPH), a mathematical model of surface tension on the molten pool morphology is established with the temperature change of molten pool being taken into account. The longitudinal morphology of molten pool and its formation process are simulated by using the SPH method under certain processing parameters, and the distributions of length and depth of molten pool are thoroughly analyzed at various processing parameters. The result shows that the longitudinal morphology of molten pool varying along the longitudinal section of solidified track presents a curve due to the influence of surface tension. A strong influence of Marangoni force on the flow of liquid metal and transformation of heat is also found. Moreover, the longitudinal morphology of a molten pool looks like that of a wave in the simulation; the deformation distributions of the longitudinal morphology of molten pool will increase with increasing laser power or decreasing scanning speed. The longitudinal morphologies of solidified molten pool are observed in the current experiments, and the experimental results are found to be agreed well with the calculated ones.
       
  • Electrophoretic deposition surfaces to enhance HFE-7200 pool boiling heat
           transfer and critical heat flux
    • Abstract: Publication date: December 2019Source: International Journal of Thermal Sciences, Volume 146Author(s): Zhen Cao, Zan Wu, Anh-Duc Pham, Bengt Sundén Modulated nanoparticle-coating surfaces were fabricated by an improved electrophoretic deposition technique in this study. Pool boiling experiments were studied for HFE-7200 on the modulated nanoparticle-coating surfaces, with a smooth surface and uniform coating surfaces as comparison. It was found that the present modulated coating surfaces can enhance the heat transfer coefficient and the critical heat flux by 60% and 20%–40%, respectively, in comparison to the smooth surface, while the uniform coating surface can improve heat transfer coefficients by maximum 100%, but cannot enhance critical heat fluxes. Heat transfer on the modulated nanoparticle-coating surfaces was theoretically analyzed by a mechanistic model which considered free convection, transient conduction and microlayer evaporation. The heat transfer can be predicted by the model, especially at low-to-moderate heat fluxes. Additionally, referring to the bubble visualization at critical heat fluxes, possible mechanisms to trigger critical heat fluxes were discussed. Afterwards, a critical heat flux model originating from the Zuber hydrodynamic instability model, was employed to predict the experimental results, showing a good prediction ability.
       
  • Experimental investigation of solar air heater with new symmetrical GAP
           ARC GEOMETRY and staggered element
    • Abstract: Publication date: December 2019Source: International Journal of Thermal Sciences, Volume 146Author(s): Jaigopal Ambade, Atul Lanjewar The paper presents experimental analysis of air flowing in solar air heater having new symmetrical gap arc geometry and staggered element. The roughness parameters are arc angle (α), relative staggered rib pitch (p'/p), number of gap on half arc (Ng), ratio of gap width to rib height (g/e) and relative staggered rib length (r/e) as 300, 0.4, 3, 4 and 4, respectively for rib diameter of 2 mm. Reynolds number and relative rib pitch were varied as 3000–15000 and 6–14, respectively. Five rib roughened plates having new symmetrical gap arc geometry and staggered element with relative rib pitch of 6, 8, 10, 12 and 14 were tested. Performance of new symmetrical gap arc geometry and staggered element has been compared with broken arc rib with staggered element and smooth duct. In new symmetrical gap arc geometry and staggered element the maximum increase in friction factor and Nusselt number corresponded to relative rib pitch of 10 and it is 3.88 and 2.18 times as compared to smooth plate. Also new symmetrical gap arc geometry and staggered element has better performance than existing best arc geometry namely broken arc rib with staggered element.
       
  • Experimental study on an acetone-charged loop heat pipe with a nickel wick
    • Abstract: Publication date: December 2019Source: International Journal of Thermal Sciences, Volume 146Author(s): Huanfa Wang, Guiping Lin, Lizhan Bai, Jingwei Fu, Dongsheng Wen In order to push forward the commercial applications of loop heat pipe (LHP) especially in an environment where people are present, it is of great importance to explore alternative working fluids to substitute the commonly used anhydrous ammonia. In this work, an acetone-charged LHP with a nickel wick is developed and experimentally studied, mainly focusing on its startup and heat transport capability. Based on the experimental results and theoretical analysis, some important conclusions have been drawn, as summarized below: 1) The acetone-charged LHP with 2 mm inner diameter pipeline can successfully realize the startup, and reach a heat transport capability of 60 W × 0.5  m; 2) When the inner diameter of the pipeline is increased from 2 to 4 mm, the LHP can start up with a much smaller heat load, i.e., 5 W, achieving a much lower steady-state operating temperature; 3) When the inner diameter of the pipeline is increased from 2 to 4 mm, the heat transport capability of the acetone-charged LHP can be increased from 60 to 100 W. 4) Adverse elevation affects greatly the heat transport capability of the acetone-charged LHP. With the adverse elevation increasing from 0 to 0.2 m, the heat transport capability is decreased from 100 to 60 W. The physical mechanisms responsible for the experimental results mentioned above have been analyzed and discussed. This work contributes to a better understanding on the operating performance and characteristics of the acetone-charged LHP, providing good design guidance and reference for its future applications.
       
  • Experimental investigation of heat transfer during flow condensation of
           HC-R600a based nano-refrigerant inside a horizontal U-shaped tube
    • Abstract: Publication date: December 2019Source: International Journal of Thermal Sciences, Volume 146Author(s): M.M. Ahmadpour, M.A. Akhavan-Behabadi This experimental study investigates the effect of MWCNT (multi-walled carbon nanotube) nanoparticles on condensation heat transfer characteristics of R600a/oil mixture inside a horizontal U-shaped tube. The experiments are organized in three parts: (i) pure refrigerant flow, (ii) refrigerant-oil mixture flow with oil mass fraction of 1%, and (iii) R600a/oil/MWCNT nano-refrigerant flow with nanoparticle mass fractions of 0.1, 0.2, and 0.3%. The condenser consists of two 135 cm straight sections and a U-bend with the inner diameter of 8.7 mm and the curve ratio of 21 installed in a 6 cm polyethylene shell. The tests are carried out in a wide range of operating conditions, including condensation pressure of 510–630 kPa, mass velocity of 140, 187, 233, and 280 kg/m2s, and vapor quality of 0.04–0.75. The results show that at low vapor quality, adding lubricating oil into the refrigerant improves the heat transfer coefficient of the mixture in comparison to the pure refrigerant, while this trend is reversed at medium and high vapor quality due to the lubricating oil impact on the condensation liquid film. In addition, the nano-refrigerant flow heat transfer coefficient increases with mass velocity while there is a critical vapor quality in which the local coefficient becomes maximum. Based on the results, using 0.3% of MWCNT causes maximum local heat transfer enhancement up to 68.2%, in comparison to the pure refrigerant. Heat transfer enhancement by adding nanoparticles is more effective at low and intermediate vapor quality.
       
  • Thermal performance and mechanisms of soot deposition in foam structured
           exhaust gas recirculation coolers
    • Abstract: Publication date: December 2019Source: International Journal of Thermal Sciences, Volume 146Author(s): M.H. Pourrezaei, M.R. Malayeri, K. Hooman Exhaust Gas Recirculation (EGR) coolers are commonly used in diesel engines to reduce NOx emissions. New diesel engine designs though require compact EGR coolers that can withstand severe deposition. This study aimed at determining the underlying mechanisms of soot deposition in metal foam structured EGR coolers. Various experiments were performed for 20 PPI aluminium foam at inlet gas temperatures of 250 and 400 °C and coolant temperatures of 25 and 90 °C to discern the importance of thermophoresis. The experimental results revealed that the thermophoresis would not be of great concern in the investigated metal foam as otherwise would have been expected in conventional flat EGR coolers. This has been attributed to the thermal equilibrium between fibers and the flue gas which was confirmed by visualization of fouled foams after experiments. In the absence of thermophoresis, isothermal soot deposition on the fibers, including interception, diffusion and inertial impaction were also investigated. For this purpose, a model is proposed to compare deposition velocities due to the aforementioned mechanisms. It is shown that interceptional deposition velocity was marginal, while inertial impaction was important for soot deposition on fibers, especially at higher inlet gas velocities and larger foam PPIs. Diffusion also made a contribution of about half of the total soot deposition on the foam ligaments at a gas velocity of 10 m/s. Finally, a comparison between foam structured and current EGR coolers showed that the higher pressure drop penalty of using foam as EGR cooler can be compensated by partial filling of the channel.
       
  • Thermodynamic performance analysis of supercritical pressure
           CO2 in tubes
    • Abstract: Publication date: December 2019Source: International Journal of Thermal Sciences, Volume 146Author(s): Haiyan Zhang, Jiangfeng Guo, Xiulan Huai, Xinying Cui Thermodynamic characteristics of supercritical pressure CO2 were numerically investigated in tubes under cooling and heating conditions. The effects of mass and heat fluxes, pressure, cross section shape and buoyancy were studied, and the determinant of the peak heat transfer coefficient was discussed. The results indicated that smaller ratio of heat flux to mass flux q/G and pressure are beneficial to the heat transfer and could lead to smaller fluid friction and entropy generation. Among three tubes with different cross sections, the circular one has the best bulk heat transfer performance in terms of both first and second laws of thermodynamics. Under heating conditions, the heat transfer deterioration may occur at the entrance when the ratio of q/G is relatively large. Replacing the circular tube with a semicircular one could alleviate local deteriorations efficiently. The local heat transfer coefficient has a lot to do with the near-wall effective thermal conductivity instead of the static thermal conductivity. The heat transfer augmentation caused by buoyancy and the deterioration mitigation in the semicircular tube could be attributed to improved near-wall effective thermal conductivity as well.
       
  • Outlining the impact of induced magnetic field and thermal radiation on
           magneto-convection flow of dissipative fluid
    • Abstract: Publication date: December 2019Source: International Journal of Thermal Sciences, Volume 146Author(s): B. Kumar, G.S. Seth, R. Nandkeolyar, A.J. Chamkha In order to deal with many scientific and technological problems such as solar dynamo and planetary problems, magnetohydrodynamics power-generation, plasma confinement, crude oil purification and rotating magnetic stars, we have investigated the steady flow of incompressible, viscous, conducting and optically thin fluid over a vertical plate with magnetohydrodynamic mixed convection, thermal radiation and viscous dissipation. The solution of governing partial differential equations is obtained by the spectral quasi-linearization method. Apart from finding solution for the induced magnetic field, velocity, and temperature, we have plotted graphs of skin friction and heat transfer coefficients for different pertinent parameters which are mentioned thereat. Results indicate that viscous dissipation has tendency to increase the temperature, induced magnetic field and velocity profiles whereas radiation parameter has opposite effect on it. Viscous dissipation and thermal buoyancy force tend to enhance the skin friction and reduce heat transfer coefficient. However, radiation parameter reduces skin friction and enhances heat transfer coefficient at the surface.
       
  • The spatial and angular domain decomposition method for radiation heat
           transfer in 2D rectangular enclosures with discontinuous boundary
           conditions
    • Abstract: Publication date: December 2019Source: International Journal of Thermal Sciences, Volume 146Author(s): Zhangmao Hu, Xuwu Zhu, Zhixiong Guo, Hong Tian, Bewen Li To remedy discontinuous boundary conditions, we propose the spatial and angular domain decomposition approach for the solution of radiative transfer equation (RTE) in a two-dimensional rectangular enclosure. The RTE is angularly and spatially discretized. For each spatial node, the total solid angle 4π is decomposed into several angular sub-domains according to the distribution of discontinuous boundaries, and the quadrature weighting factors are recalculated for each angular sub-domain by using the compound trapezoidal integral scheme. For each angularly-discretized direction, the spatial domain is decomposed into a few spatial sub-domains according to the distribution of discontinuous boundaries. In each spatial sub-domain the distribution of radiative intensity is continuous, and the angularly-discretized RTE is solved for each spatial sub-domain. Two examples are employed to verify the performance of the domain decomposition method, and the results confirm its suitability and advantage for treating radiative transfer problem with discontinuous boundary conditions.
       
  • Stability of the horizontal throughflow of a power-law fluid in a
           double-diffusive porous layer under convective boundary conditions
    • Abstract: Publication date: December 2019Source: International Journal of Thermal Sciences, Volume 146Author(s): Seema Kumari, P.V.S.N. Murthy Double-diffusive convective instability of a horizontal througflow in a power-law fluid-saturated porous layer lying between infinitely extended two plane horizontal boundaries is investigated by considering internal heating associated with the viscous dissipation. These boundaries are assumed to be impermeable, isosolutal and are subjected to the third kind thermal boundary conditions which are characterized by different Biot numbers B0,B1. The linear stability analysis of basic flow for pseudoplastic and dilatant fluids is analyzed for the longitudinal and transverse rolls in both aiding and opposing buoyancy cases. The eigenvalue problem is solved numerically using the bvp4c in Matlab. It is shown that the longitudinal rolls are the most unstable mode for dilatant fluids, whereas the transverse rolls are the most unstable mode of disturbance for pseudoplastic fluids. In both these cases, an increase in either of these Biot numbers is enhancing the stability of power-law fluids. Increasing Pèclet number destabilized the transverse rolls for the pseudoplastic fluid while the longitudinal rolls are stabilized in case of the dilatant fluid. The effect of viscous dissipation on the onset of instability is also presented. A discussion on the onset of oscillatory convective instability (ω≠0) in this double-diffusive process, under third kind thermal boundary conditions is also presented. Further, the instability of power-law fluid is discussed for two limiting cases of thermal boundary conditions; the first one is B0=0,B1→∞ which corresponds to the constant heat flux at the bottom boundary while the second one is B0→∞,B1→∞, that corresponds to isothermal walls. As Pe=0 is a singularity for the eigenvalue problem, a detailed asymptotic analysis of Pe→0 is presented for all these cases.
       
  • Experimental investigation on thermal cracking and convective heat
           transfer characteristics of aviation kerosene RP-3 in a vertical tube
           under supercritical pressures
    • Abstract: Publication date: December 2019Source: International Journal of Thermal Sciences, Volume 146Author(s): Si Jiao, Sufen Li, Hang Pu, Ming Dong, Yan Shang This study experimentally investigated the pyrolysis and heat transfer characteristics of a specific EHF (aviation kerosene RP-3) flowing in a vertical upward tube under supercritical pressures (2.5–5.5 MPa). Three wall heat flux conditions, i.e. 700, 950, and 1240 kW/m2 are designed to represent the condition with no significant cracked, mildly cracked, and deeply cracked of fuel, respectively. The results show that the elevated pressure could impact on the reaction pathway of alkanes and alkenes, resulting in a smaller alkene/alkane ratio and less endothermicity. A promoting effect of the elevated pressure and heat flux on the conversion and gas yield is confirmed in this work. Then heat transfer characteristics are analyzed in detail based on the wall temperature and the local (apparent)/average HTC distributions. The buoyancy effect causes the deterioration of heat transfer under high heat flux. The elevated pressure decreases the maximum wall temperature whereas enlarges the range of heat transfer deterioration region. A conclusion could be obtained that the increase of pressure has little effect on alleviating of heat transfer deterioration under rather large heat flux conditions. The average HTCs in the cracked region is twice larger than that in the non-cracked region, indicating that the pyrolysis improves the heat transfer of fuel. Besides, it is found that the influence of pressure on heat transfer characteristic is dominated by the isobaric specific heat capacity and density in the non-cracked region and the cracked region, respectively. Furthermore, the effect of pyrolysis on heat transfer deterioration is investigated. It is found that the strong pyrolysis reaction near the wall is beneficial to lower the wall temperature in the HTD region, and the buoyancy effect is not significantly increased by the further decrease in fluid density caused by pyrolysis.
       
  • Numerical study of MHD mixed convection flow over a diamond-shaped
           obstacle using OpenFOAM
    • Abstract: Publication date: December 2019Source: International Journal of Thermal Sciences, Volume 146Author(s): Ranjit J. Singh, Trushar B. Gohil The development of the flow structure with assisting the buoyancy in the liquid metal flow over the diamond-shaped obstacle and the influence of the presence of magnetic field on the vorticity and heat dissipation from the hot surface is investigated numerically at fixed Reynolds number of Re = 1000. The computation is performed by the in-house developed magnetohydrodynamics (MHD) based flow solver using open source CFD tool OpenFOAM. The liquid metal with a Prandtl number of Pr = 0.02 is considered as working fluid and is assumed to be electrically conducting in nature. The strength of the buoyancy in the flow is varied in the range of four different Richardson number of Ri = 0, 0.5, 1, and 5. The consequence of the rising buoyancy in the flow on the vorticity and time-averaged Nusselt number over the hot surface is observed. The unsteadiness in the flow due to the rise in the buoyancy is further controlled and regulated by the application of a magnetic field. The intensity of the magnetic field is governed by non-dimensional Hartmann number (Ha) varies in the range of Ha = 0–50. It is observed from the results that the Lorentz force in the flow opposes the Kármán vortex street and the buoyancy in the flow degenerates the vortex. The undulation in the heat transfer due to rise in the buoyancy is suppressed by the presence of Lorentz force without sacrificing the Nusselt number at low Hartmann number. The study of isotherms, streamlines, time-averaged Nussselt number, vorticity is discussed in detail.
       
  • Thermodynamic modeling and artificial neural network of air counterflow
           vortex tubes
    • Abstract: Publication date: December 2019Source: International Journal of Thermal Sciences, Volume 146Author(s): Junior Lagrandeur, Sébastien Poncet, Mikhail Sorin, Mohammed Khennich A large number of operational and geometrical parameters are involved in the optimization of counterflow vortex tubes. The number of parameters is so important that most researchers relied on a one factor at a time approach which cannot capture the possible interactions between the relevant parameters. Additionally, literature contains very few information on how to design properly a vortex tube for given inlet conditions.To identify the most important features, two approaches are used: artificial neural networks (ANNs) and thermodynamic modeling. Both methods could reproduce accurately the cold outlet temperature of vortex tubes from the literature. To achieve this, the ANN uses only the inlet pressure, the cold mass fraction, the length to the diameter ratio and the cold outlet diameter to the vortex diameter ratio. The output from another ANN is the inlet mass flow rate. This second ANN uses only the inlet pressure, the length to diameter ratio, the total inlet nozzles’ area and the vortex tube diameter as inputs to do the calculation.The most important parameter in the thermodynamic model is the inlet pressure to cold outlet pressure ratio. It is shown that the variations of this ratio by friction in the inlet nozzles are not negligible and should be considered in future vortex tubes’ design. The Bödewadt boundary layer flow between the inlet and the cold outlet affects also significantly the vortex tube performance.
       
  • On thermal performance of serpentine silicon microchannels
    • Abstract: Publication date: December 2019Source: International Journal of Thermal Sciences, Volume 146Author(s): Dungali Sreehari, Apurbba Kumar Sharma In the present study, three different serpentine microchannels (Rectangular, U and V) of rectangular cross-section with a channel span 24 mm were fabricated on a 0.525 mm thick (100) silicon substrate using micro-ultrasonic machining (micro-USM) technique. Thermal performance of the microchannels was experimentally investigated by making the working fluid (water) to flow through them at different Reynolds numbers (100–400) and at different heat fluxes (10 kW/m2, 20 kW/m2 and 30 kW/m2). Similar microchannels were modeled and analysed numerically simulating the experimental conditions. The performances of the microchannels obtained with the experimental as well as numerical results were compared in terms of pressure drop, substrate and fluid temperatures and heat transfer coefficient. The results indicate that the overall thermal performance of the microchannel heat sink mostly depends on the type of pattern as the fluid-substrate interaction area, defined by the Sink Area Factor (SAF), changes appreciably with the pattern. It was found that the U-serpentine microchannel exhibited the best thermal performance while compared to the other two serpentine microchannels. The sharp bends of the microchannel patterns and the surface roughness of the microchannel walls adversely affect the overall thermal performance of the microchannels. The study also outlines the need for a compromise in the Reynolds number, as higher Reynolds number tends to lower the overall thermal performance of the microchannels.
       
  • Numerical simulation and analysis of heat leakage reduction in loop heat
           pipe with carbon fiber capillary wick
    • Abstract: Publication date: December 2019Source: International Journal of Thermal Sciences, Volume 146Author(s): Yixue Zhang, Junyu Liu, Longfei Liu, Haolin Jiang, Tao Luan In this paper, a loop heat pipe (LHP) with a carbon fiber capillary wick was taken as the research object to study the steady state inside the LHP and validate the effectiveness of proposed improvements through CFD numerical simulations. A 3D model of the LHP was built and numerical simulations of steady state operation were conducted by ANSYS software. Through comparison of experiment and simulation results, heat leakage from the heated surface to the compensation chamber (CC) was identified as the major cause of failure in the feasibility experiment. The addition of a heat insulation layer on the contact surface between shells of the evaporator and the compensator was validated as an improvement in reducing heat leaking through the metal shells. The substitute of the copper plating by an alumina-copper coating on surface of the carbon fiber capillary wick was proposed as an improvement to decrease the heat transferring through the capillary wick. The simulation shows that a silicon sheet with low thermal conductivity can increase the liquid volume fraction in the CC to 23%, while an yttria-stabilized zirconia (YSZ) heat insulation layer can raise the figure to 74%. According to simulation results, the combination of YSZ layer and alumina-copper coating can realize a temperature drop of 5.7 K comparing with the combination of silicon sheet and copper plating. The optimized experiment indicates that the use of the heat insulation layers improves stability of operation and increases bearing heat load of the LHP. The dependability of simulation results and the rationality of experimental error were proved by comparing results of experiment and simulation under the same operation conditions.
       
  • Large eddy simulation of turbulent heat transfer in a non-isothermal
           channel: Effects of temperature-dependent viscosity and thermal
           conductivity
    • Abstract: Publication date: December 2019Source: International Journal of Thermal Sciences, Volume 146Author(s): Lei Wang, Jian Liu, Safeer Hussain, Bengt Sundén In this work, we perform large eddy simulations (LES) to study the influence of variable viscosity and thermal conductivity on forced convection in a non-isothermal channel flow. To prevent thermal dilatational effect, the gas density is assumed to be constant. The temperature ratio T2/T1 is varied from 1.01 to 2.2, where T2 and T1 are the temperatures of hot and cold walls, respectively. The mean turbulent Reynolds number is kept the same at 395. The results indicated that the mean flow fields are significantly affected by the temperature-dependent fluid properties. Despite the modified velocity and temperature profiles, it is interesting to note that the molecular momentum and heat transport across the channel remain unchanged. Meanwhile, pronounced differences are exhibited for various turbulence statistics such as root-mean-square velocity and temperature fluctuations, Reynolds shear stress, and correlation between streamwise velocity and temperature. Compared with the isothermal flows, it is also found that the presence of the temperature gradient tends to diminish heat transfer. With increasing the temperature ratio, the Nusselt numbers for both sides are reduced. Moreover, the hot side has a higher Nusselt number than the one at the cold side.
       
  • Multiphase flow and boiling heat transfer modelling of nanofluids in
           horizontal tubes embedded in a metal foam
    • Abstract: Publication date: December 2019Source: International Journal of Thermal Sciences, Volume 146Author(s): Hayder I. Mohammed, Pouyan T. sardari, Donald Giddings The aim of this numerical study is to evaluate the boiling process of nanofluid in horizontal tubes in the presence of a metal foam as porous medium and represent the experimental work of Zhao et al. in a numerical aspect with a different range of dependent variables. High conductive metal foams are employed to increase the rate of heat transfer and enhance the boiling performance in the domain. Two-phase mixture model is used to simulate the characteristics of nanofluid and solve the governing equations in a two-phase flow and boiling heat transfer problem. R134a and ZnO are considered as the base-fluid and nanoparticles, respectively. The characteristics of metal foam including the porosity and pore density as well as operating conditions including the fluid flow including the velocity, induced heat flux and concentration of nanoparticles on the pressure drop, vapour volume fraction and heat transfer coefficient are examined. The results show the positive effect of the metal foam on vapour production and overall heat transfer coefficient of the nanofluid in the pipe outlet; however, due to the flow resistance as a result of porous medium addition, a higher pressure drop is achieved. For the heat flux of 19 kW/m2 and inlet velocity of 0.05 m/s, by using a metal foam with the porosity of 70% and pore density of 20PPI, the vapour volume fraction, heat transfer coefficient and pressure drop enhances by 7.1%, 9.4% and 82.7%, respectively, compared with the case of without metal foam. However, by using the porosity of 90%, the vapour volume fraction, heat transfer coefficient and pressure drop enhances by 1.6%, 3.5%, and 7.0%, respectively. Consequently, according to the developed results in this paper, a system with a moderate to low porosity with a high to moderate pore density is recommended which is finally determined based on the required vapour production and allowed pressure drop.
       
  • Study on transient heat flux intensity factor with interaction integral
    • Abstract: Publication date: December 2019Source: International Journal of Thermal Sciences, Volume 146Author(s): Huachao Deng, Bo Yan, Honghong Su, Xiaomin Zhang, Xin Lv Aim at determining of the heat flux intensity factor (HFIF) near a crack tip in structures under transient heat flux load, the transient JT integral is defined firstly and proved to be path-independent. Based on the path-independence of the transient JT integral, a transient interaction integral utilized to extract the transient HFIF is established by introducing a known auxiliary field. A singular isoparametric quadrilateral element with eight nodes, which is used to discretize the structure around the crack tip, by moving the midside nodes to one-fourth of the sides is presented. With this singular element, the 1/r singularity of heat flux near the crack tip can be exactly depicted. Numerical examples are carried out to verify the path-independence of the transient JT integral and the interaction integral method to extract the transient HFIF. Moreover, the transient HFIF in a structure with multiple cracks are numerically investigated by means of the presented method. The method proposed in this paper can be extended to investigate the thermo-mechanical problems.
       
  • Climatology in shallow caves with negligible ventilation: Heat and mass
           transfer
    • Abstract: Publication date: December 2019Source: International Journal of Thermal Sciences, Volume 146Author(s): Béatrice Guerrier, Frédéric Doumenc, Aymeric Roux, Sophie Mergui, Pierre-Yves Jeannin The present numerical study investigates the effect of a cavity located at shallow depth below ground surface. The temperature field in the rock matrix surrounding the cave is significantly deformed compared to the case without cavity. Fluxes at cave wall, related to radiation, air-convection and evaporation/condensation (in case of a humid cave), all contribute to a significant homogenisation of wall temperatures. In case of high humidity, simulations of evaporation/condensation periods show that some parts of the wall may be durably (several months) subjected to significant condensation (or evaporation). Real meteorological data, i.e. 77 years of external temperature data of the Gourdon station in France, have been used as input of the model. Results of simulations have been compared to experimental temperature of Lascaux cave, with good agreement considering some simplifying hypotheses assumed for this modeling. The asset of such a model is the low computing time required to simulate several years, and thus its ability to follow long time evolution. Results significantly improve our understanding of conditions taking place in a shallow cavity, what will help improving the management of caves, especially those with very fragile decorations such as Paleolithic paintings. The model may help to identify areas which are the most exposed to weathering and to test the effect of past and potential changes in nearby conditions. It may also be useful for managing shallow underground constructions (e.g. a mine or even a cellar).Graphical abstractImage 1
       
  • Experimental and numerical investigation of liquid-cooled heat sinks
           designed by topology optimization
    • Abstract: Publication date: December 2019Source: International Journal of Thermal Sciences, Volume 146Author(s): Hao Li, Xiaohong Ding, Dalei Jing, Min Xiong, Fanzhen Meng In order to study the relationship between the thermal-hydraulic performances and the layout of cooling channels designed by topology optimization from the engineering perspective, two types of topology optimization problems are studied. The first is the flow distribution problem that is to achieve the minimization of power dissipation under the flow rate quality constraints, and the second is the heat exchange maximization problem that is to achieve the optimal thermal performances under the constant input power constraint. Then the optimized heat sinks together with a conventional S-shaped channel heat sinks are manufactured and their thermal-hydraulic performances are investigated both numerically and experimentally. The results reveal that the flow distribution design can provide the lowest hydraulic resistance while the heat exchange maximization design can keep the thermal resistance to a minimum. The proposed design method can be used as a tool to provide cooling solutions to the thermal management of high heat flux electronic components.Graphical abstractIn order to study the relationship between the thermal-hydraulic performances and the layout of cooling channels designed by topology optimization from the engineering perspective, two types of topology optimization problems are studied. The first is the flow distribution problem that is to achieve the minimization of power dissipation under the flow rate quality constraints, and the second is the heat exchange maximization problem that is to achieve the optimal thermal performances under the constant input power constraint. Then the optimized heat sinks together with a conventional S-shaped channel heat sinks are manufactured and their thermal-hydraulic performances are investigated both numerically and experimentally. The results reveal that the flow distribution design can provide the lowest hydraulic resistance while the heat exchange maximization design can keep the thermal resistance to a minimum. The proposed design method can be used as a tool to provide cooling solutions to the thermal management of high heat flux electronic components.Image 1
       
  • Polymeric hollow fibers: A supercompact cooling of Li-ion cells
    • Abstract: Publication date: December 2019Source: International Journal of Thermal Sciences, Volume 146Author(s): Jan Bohacek, Miroslav Raudensky, Tereza Kroulikova, Ebrahim Karimi-Sibaki An unconventional design of the heat exchanger has been introduced for conventional liquid cooled systems of battery modules/packs of electric vehicles (EVs). It is deemed unconventional, because only non-metallic materials are used, namely polydicyclopentadiene (PDCPD) as a mechanical housing and polymeric hollow fibers as coolant channels. The heat exchanger is lightweight, electrically non-conductive, durable, wear resistant, low cost, manufacturable. Very small in diameter (
       
  • Analysis of spectral radiative entropy generation in a non-gray planar
           participating medium at radiative equilibrium with two different boundary
           conditions
    • Abstract: Publication date: December 2019Source: International Journal of Thermal Sciences, Volume 146Author(s): Asadollah Bahrami, Ali Safavinejad, Hossein Amiri In the present study, spectral radiative entropy generation analysis is presented for radiative heat transfer between two parallel plates containing non-gray absorbing and emitting medium at radiative equilibrium. In order to evaluate the effect of boundary condition (BC) on the entropy generation, two configurations of BC are considered. In the first configuration, two bounding walls are assumed to be at prescribed temperatures. In the second configuration, one wall is assumed to be at a prescribed temperature and the other wall is assumed to have prescribed heat flux BC. The discrete ordinates method and the finite volume method are respectively used for the angular and spatial discretization of the radiative transfer equation and radiative entropy generation equations. While the correlated-k (CK) non-gray model is used to evaluate spectral radiative properties. Five cases are considered, including two homogeneous cases and two non-homogeneous cases with a single participating gas (i.e. H2O or CO2) and one homogeneous case with a mixture of H2O, CO2 and soot particles. Spectral, volumetric and total radiative entropy generations are calculated for each BC configuration and case. Also, the effects of the concentration of participating gas, wall emissivity and total gas pressure on radiative entropy generation are attentively analyzed. The results show that irreversible radiative transfer at the wall with lower temperature is the main source of radiative entropy generation in the system. Soot particles increase radiative entropy generation due to absorption and emission process but decrease radiative entropy generation due to walls radiation. The radiative entropy generation is approximately constant when the concentration of participating gas varies for both BC's. Total radiative entropy generation for the system with the prescribed temperature at walls significantly increases with the increase of wall emissivity; conversely, for the system with mixed BC, total radiative entropy generation linearly decreases. Furthermore, for the system with the prescribed temperature at the walls, radiative entropy generation slightly decreases when medium total pressure increases; while for the problems with mixed BC, increasing medium total pressure does not significantly effect on radiative entropy generation. Finally, results demonstrate that the wall emissivity has a considerable effect on the radiative entropy generation for radiative heat transfer in the non-gray medium in radiative equilibrium.
       
  • Experimental study on the air-side thermal-flow performance of additively
           manufactured heat exchangers with novel fin designs
    • Abstract: Publication date: December 2019Source: International Journal of Thermal Sciences, Volume 146Author(s): Sebastian Unger, Matthias Beyer, Samira Gruber, Robin Willner, Uwe Hampel We introduce novel fin designs for finned tube heat exchangers which enhance the conduction heat transfer within the fin and the convective heat transfer along the fin surface simultaneously. Oval tubes with circular plain fins (CPF), circular integrated pin fins (CIPF) and a serrated integrated pin fins (SIPF) were additively manufactured via Selective Laser Melting (SLM) and their heat transfer and flow characteristics studied in a flow channel for different Reynolds number between 1800 and 7800 as well as fin spacing values between 6mm and 16mm. From the experiments an improvement of Nusselt number and a reduction of friction factor was found for all fin designs when fin spacing increases. CIPF showed a higher Nusselt number compared to CPF at all Reynolds numbers and fin spacing values. The highest Nusselt number as well as moderate friction factor values were found for the SIPF design. However, for SIPF the fin efficiency of 30.3% is lowest due to the high heat dissipation along the fin surface. In order to evaluate the thermal and flow performance three parameters were studied: the performance evaluation criterion, the volumetric heat flux density and the global performance. CIPF gives a higher performance evaluation criterion compared to CPF and SIPF performs best compared to the other fin designs. Highest volumetric heat flux density of 2.72kWm³K was achieved with CIPF at lowest fin spacing. Small differences in the global performance criterion between the fin designs and for various fin spacing were observed. The SIPF design is of advantage, if the required surface area, the material cost and the weight of the finned tube heat exchanger are relevant. From the experimental results a heat transfer correlation that includes Nusselt number, Reynolds number, Prandtl number, fin spacing and fin design has been derived.
       
  • Combination of the Monte Carlo method and DDA to evaluate the radiative
           properties of ITO- pigmented and TiO2-pigmented coatings
    • Abstract: Publication date: December 2019Source: International Journal of Thermal Sciences, Volume 146Author(s): Yujia Bao, Yong Huang, Wen Li, Keyong Zhu Indium tin oxide (ITO) and titanium dioxide (TiO2) are both widely used as pigments for thermal barrier coatings. Instead of being assumed to be the overall spherical particles, the ITO and TiO2 pigment particles in the coatings were modeled as clusters with connected structures to simulate the morphology of the fractal aggregates that are shown in the transmission electron microscope (TEM) images. The ball-necking factor η was applied to quantify the connectors by utilizing the particle superposition model. A approach, which combined the Monte Carlo method and discrete dipole approximation (DDA), was applied to evaluate the reflective and absorptive performances of the functional coatings that were pigmented with the ITO and TiO2 fractal clusters. This approach considered the effects of the pigments with fractal aggregate structures on the scattering properties, including the phase functions and asymmetry factor. These parameters reflected the dependence of the scattering intensity on scattering angles and the radiative transfer directions of the beams in the coatings and had a subsequent influence on the coatings’ absorptivity. Based on the Monte Carlo-DDA method, the impacts of the cluster material, ambient media, coating thicknesses and volume fraction of the pigment clusters on the coatings absorption rates were discussed.
       
  • Collocation method with fractional powers exponential trial functions for
           singularly perturbed reaction-convection-diffusion equation
    • Abstract: Publication date: December 2019Source: International Journal of Thermal Sciences, Volume 146Author(s): Chein-Shan Liu, Chih-Wen Chang We develop a collocation method for solving the singularly perturbed convection-diffusion equation and reaction-diffusion equation of elliptic type partial differential equations. When the singularly perturbed solution is expressed in terms of a set of fractional powers 2D exponential trial functions, and collocate points to satisfy the boundary conditions and the governing equation, we can obtain a small scale normal linear system, which is solved by the Gaussian elimination method or the conjugate gradient method to determine the expansion coefficients. The numerical algorithm with complexity O(n) is very time saving, effective and accurate to find the solutions of highly singularly perturbed reaction-convection-diffusion problems, which are defined in a rectangular domain as well as in an arbitrary domain, and the numerical examples together with an experimental result confirm the assessments.
       
  • Study of drying process a vertical porous channel by developing a numeric
           solver in OpenFOAM
    • Abstract: Publication date: December 2019Source: International Journal of Thermal Sciences, Volume 146Author(s): Hassan Gholami, Ramin Kouhikamali, Navid Sharifi In this study, the phenomenon of evaporation in a porous medium of a vertical channel is analyzed. Numerical simulations of the partial evaporation process of the water in porous channel is conducted using an In-house developed code. First, by adding the thermal phase change to the base solver, the solver containing the evaporation phenomenon was generated and then, considering the hydrodynamic and thermophysical characteristics of the porous region, the final solver was obtained. The Initial state of the system consists of a water phase and a porous medium made of copper particles. However, with the partial evaporation of water, the vapor phase appears as the second fluid phase. It was assumed that water and vapor are incompressible and incompatible and the phenomenon of evaporation occurs unevenly. The Volume of fluid method (VOF) governs the interface between phases and the Lee model was used to account for the mass transfer between liquid and vapor phases. For surface tension between phases, the continuous surface force method was considered. Comparison of simulation results with experimental results showed that the new solver could well estimate the evaporation rate in different sections of the channel. The characteristics of this flow were introduced by examining the distribution of water volume fractions, temperature variations, time evolution of the porous channel drying process, porosity, permeability and contact angle between fluid phases and wall.
       
  • Effects of new methods of porosity arrangement on forced convection in a
           variable BDPM using numerical simulation
    • Abstract: Publication date: December 2019Source: International Journal of Thermal Sciences, Volume 146Author(s): Behnam Rajabzadeh, Mohammad Hojaji Najafabadi, Arash Karimipour In this study, forced convection the heat generation components by cooling porous elements has been investigated using BDPM method. A developed code under FVM and Simple Algorithm is used for numerical simulation. Air is selected as the working fluid with Pr = 0.7 in the laminar state. Effects of variable permeability distribution was investigated by changing the permeability in each column of porous blocks in increasing, decreasing, sinusoidal, and cosine patterns. In addition, the influences of average Darcy number and Darcy domain alterations of the porous blocks has been simulated. Sinusoidal pattern has the largest system performance under Re = 400–1000. In comparison with constant pattern, system performance has increased up to 9.5 times for sinusoidal pattern. Likewise, heat transfer in variable pattern is greater than constant one. The effects of variable pattern become more evident by changing average Darcy number since Darcy reaches 10−3, which will optimize heat transfer and system performance. Based on Darcy domain changes in the columns, it could be found that Darcy domain also affects heat transfer and pressure drop. These changes in Darcy domain can increase the system performance up to about 2.2 times.
       
  • Performance comparison of wavy microchannel heat sinks with wavy bottom
           rib and side rib designs
    • Abstract: Publication date: December 2019Source: International Journal of Thermal Sciences, Volume 146Author(s): Ji-Feng Zhu, Xian-Yang Li, Shuo-Lin Wang, Yan-Ru Yang, Xiao-Dong Wang Employing wavy microchannels has been proven to enhance the heat transfer performance of microchannel heat sinks as compared to employing straight microchannels, and the heat transfer enhancement is much larger than the pressure drop penalty. The wavy microchannels have been adopted on the side walls of microchannels or top and bottom walls; however, it is still a pending issue that which scheme should be adopted in practical applications. In this work, a three-dimensional fluid-solid conjugate model is developed to investigate the heat transfer performance of the left-right and up-down wavy microchannel heat sinks. With the same pumping power and channel cross-section area, the global thermal resistance and the maximum bottom wall temperature variation of the two wavy designs are compared for various wavy amplitudes, wavelengths, channel aspect ratios, and width ratios of channel to pitch. The simulations show that the both wavy designs induce a symmetric pair of counter rotating Dean vortices in the plane of the channel cross-section, which enhances the coolant mixing and thus improves the heat sink performance. The Dean vortices induced by the up-down wavy design are located near the side walls of channels, whereas they are generated near the top and bottom walls of channels for the left-right wavy design. Regardless of amplitude, channel aspect ratio, and width ratio of channel to pitch, the up-down wavy design exhibits a better heat transfer performance than the left-right one when small wavelengths are adopted; however, at large wavelengths, the two designs show almost the same performance. The above results can be attributed to the different Dean vortices induced by the two designs. The Dean vortices generated in the up-down wavy design mix the flow between the hot bottom portion and the cool top portion of channels, whereas the Dean vortices generated in the left-right wavy design are confined to near either the hot bottom or the cool top. Thus, the up-down wavy design should perform better in general. The results obtained here can provide a useful guidance for the optimal design of wavy microchannel heat sinks.
       
  • Heat transfer optimization of twin turbulent sweeping impinging jets
    • Abstract: Publication date: December 2019Source: International Journal of Thermal Sciences, Volume 146Author(s): Amirsaman Eghtesad, Mohammadamin Mahmoudabadbozchelou, Hossein Afshin In this study, a numerical investigation is carried out to reveal the potential of obtaining uniform cooling on a planar surface by impinging jets in a turbulent flow regime using the SST k−ω turbulence model. Twin turbulent sweeping impinging jets (TTSIJ), as an idealization of an array of jets, are considered for heat transfer with the planar target surface. Unlike other studies that focused on a few effective parameters or limited the impinging jets to certain conditions, in this study, a more general investigation is performed to clarify the effects of all influential parameters on heat transfer. To this end, the effects of 8 design variables namely Reynolds number, the jet-to-target distance, the phase shift between the two jets, the frequency of pulsations of jets, the frequency of sweeping motion, the jet-to-jet separation distance, the hydraulic diameter of the nozzles, and the maximum of sweeping angle of the nozzles on Nusselt distribution on the target surface are evaluated. For the purpose of elimination of thermal stress on the target surface, it is attempted to optimize the design variables to reach a uniformly distributed Nusselt number on the target surface for 9 design uniform Nusselt distribution. The optimization of the design variables is performed using artificial neural network (ANN) combined with genetic algorithm (GA) to minimize the discrepancy between the ideally uniform and optimized Nusselt distribution. Results show that within the assumed bounds of the design variables, the applied method is successful in obtaining uniform cooling with the accuracy of more than 98% and 93% in the best and worst situation, respectively.
       
  • Analysis of straight and wavy miniature heat sinks equipped with straight
           and wavy pin-fins
    • Abstract: Publication date: December 2019Source: International Journal of Thermal Sciences, Volume 146Author(s): Zohreh Chamanroy, Morteza Khoshvaght-Aliabadi The use of pin-fins is an effective technique for improving the performance of miniature heat sinks. Generally, this improvement is due to the larger heat transfer area as well as the chaotic advection of fluid and thermal boundary layer interruption, which are produced by pin-fins. In this analysis, the performance of straight miniature heat sink (SMHS) and wavy miniature heat sink (WMHS) is investigated in the presence of straight and wavy pin-fins and the obtained results are compared with the smooth cases. Results show us that noticeable differences of velocity and temperature fields between the enhanced cases and the smooth cases exist, and they differ from shape to shape of channel and pin-fin. It is also found that both the heat transfer coefficient and the pressure drop of SMHSs and WMHSs equipped with pin-fins are always higher than those of without pin-fins. At the studied range of Reynolds number (i.e. 100 to 1000), the enhanced cases show 0.05 to 2.3 times enhancement in the heat transfer coefficient and 2.6 to 13.6 times augmentation in the pressure drop compared with the smooth cases. The highest values are recorded for the WMHS equipped with wavy pin-fins having an opposite spin. However, it is shown that for the same pumping power the heat removal of all enhanced cases is higher than that in the smooth cases. Overall analysis using the ratio of heat transfer rate to pumping power is done to detect the best configuration: a better performance is observed for the SMHS with straight pin-fins and the WMHS with wavy pin-fins having an identical spin.Graphical abstractImage 1
       
  • Quantitative evaluation of emission properties and thermal hysteresis in
           the mid-infrared for a single thin film of vanadium dioxide on a silicon
           substrate
    • Abstract: Publication date: December 2019Source: International Journal of Thermal Sciences, Volume 146Author(s): Gianmario Cesarini, Grigore Leahu, Alessandro Belardini, Marco Centini, Roberto Li Voti, Concita Sibilia We present a comparative study of the emission properties of a vanadium dioxide thin film (approximately 200 nm) deposited on a silicon wafer in different sub-spectral-ranges of the mid-infrared, with particular attention to the windows of transparency of the atmosphere to the infrared radiation (i.e., 3–5 μm, 8–12 μm). The infrared emission properties of the structure are closely related to the well-known phase transition of the first order, from semiconductor to metal, of the vanadium dioxide around the temperature of 68 °C. The characterization of the emissivity in the sub-regions of the mid-infrared was carried out both in the front configuration, that is on the VO2 film side, and in the rear configuration on the silicon wafer side, and showed a strong difference in the hysteresis thermal bandwidth, in particular between the short wave region and the long wave region. The bandwidth is equal to 12 °C for the front and 15 °C for the rear. The emissivity behaviors as a function of temperature during the semiconductor-metal transition in the mid-infrared subregions were analyzed and explained using the theories of the effective medium of Maxwell Garnett and Bruggeman, highlighting the greater functionality of one theory with respect to the other depending on the spectral detection band.
       
  • Effect of heat transfer and geometry on micro-thruster performance
    • Abstract: Publication date: December 2019Source: International Journal of Thermal Sciences, Volume 146Author(s): K.M. Muhammed Rafi, M. Deepu, G. Rajesh Coupled Navier-Stokes and Direct Simulation Monte Carlo (NS-DSMC) simulations of gas flow in micro-nozzles for various wall thermal conditions and geometrical aspects are presented. Micro-thrusters employed in miniature spacecraft and microsatellites experience substantial changes in wall thermal conditions. This can influence the internal boundary layer development and the exit plume structure of a micro-nozzle. These changes in flow physics differ with the nozzle divergence angle and the proximity of a similar nozzle in the cluster. Continuum solvers often fail to analyze the micro-nozzles operating in vacuum conditions as the flow in micro-nozzles experiences continuum, transitional, and rarefied regimes. Coupled NS-DSMC solver is an effective alternative that can simulate the non-equilibrium effects in a micro-nozzle flow field. A steady solution of the entire flow field has been obtained using a non-linear Harten-Lax-van Leer-Contact (HLLC) scheme based finite volume solver with a higher order slip boundary condition. Continuum breakdown regions are identified based on the gradient-length local (GLL) Knudsen number condition. This initial steady solution on the flow transition boundary is implemented in the DSMC solver as a Dirichlet boundary condition. The present computations are useful in calibrating micro-propulsion controllers to adapt to the substantial momentum changes associated with various nozzle wall thermal conditions and the proximity of similar nozzles in the cluster.
       
  • Numerical investigation on buoyancy and inclination effects on transient
           mixed convection in a channel with discretely heated plane symmetric
           contraction-expansions
    • Abstract: Publication date: December 2019Source: International Journal of Thermal Sciences, Volume 146Author(s): F. García, C. Treviño, E. Salcedo, L. Martínez-Suástegui In this work, transient mixed convection in a channel with discretely heated plane symmetric contraction-expansions at the mid-channel section emulating electronic components is studied numerically. The facing walls of the obstructions are isothermal, the other bounding walls of the constriction and the channel have non-adiabatic walls. The impact of changes in the cross section and their corresponding sensitivity to duct orientation on the overall flow and thermal evolution in space and time is analysed for fixed Prandtl number of Pr=7, Reynolds number in the range 100 ≤Re≤ 1000, channel inclination of 0∘≤Γ≤90∘, and different values of buoyancy strength (Richardson number). Results indicate that as the duct approaches the horizontal configuration, buoyancy strength reduces and higher threshold values of the Richardson number are required to induce instability. Also, depending on the parametric set, the flow and temperature distributions can experience an oscillatory behavior associated to variations in size of a complex vortical structure that occupies the spatial region near the partial blockage and that extends to downstream positions of the latter. Numerical predictions demonstrate how the blockage height affects the wake structure and vortex dynamics, and the effects of the Prandtl number and heat losses to the channel walls on the evolution of the flow and heat transfer response are presented and discussed in detail.
       
  • Detailed heat transfer investigation of an impingement jet array with
           large jet-to-jet distance
    • Abstract: Publication date: December 2019Source: International Journal of Thermal Sciences, Volume 146Author(s): Lingling Chen, Robin G.A. Brakmann, Bernhard Weigand, Michael Crawford, Rico Poser The heat transfer performance of a large jet-to-jet distance impingement configuration with a jet-to-jet spacing X/D = Y/D = 10 was experimentally studied for turbomachinery applications. Narrowband thermochromic liquid crystals (TLCs) were used to record the target wall temperature. Pressure taps were set along the experimental rig to measure the pressure loss. Improved measurement methods with multiple TLCs and a ramp heater were studied. The work was done for different Reynolds numbers (Re = 15,000–35,000), different jet to target plate distances (H/D = 3–5) and different cross-flow schemes. The results from the improved methods show good agreement with the basic measurement method. It confirms that the single TLC, step heater method is sufficient for the current experimental study. The improved methods are confirmed to be reliable and are suitable for complex applications with extremely large heat transfer variations over the measured surface, or extremely high local heat transfer coefficients. Experimental results indicate that a smaller jet to target plate distance and a smaller cross-flow scheme can provide a better heat transfer performance in the studied range. When compared to the impingement configuration with X/D = Y/D = 5, the results show that a larger jet-to-jet distance configuration provides a higher overall heat transfer when the mass flow rate is kept constant.
       
  • On the development of an optimized multiprobe cryo-ablation plan using
           immerse boundary method and genetic algorithm
    • Abstract: Publication date: December 2019Source: International Journal of Thermal Sciences, Volume 146Author(s): Y.L. Shao, S.C. Chen, M.R. Islam, H.L. Leo, K.J. Chua Cryosurgery is becoming an effective method to treat undesired tumor tissue via the application of extremely low temperature coolant flowing through a probe. To maximize cryoinjury in the targeted tumor region, multiple cryoprobes are simultaneously employed to freeze the surrounding tumor tissues. In order to minimize cryosurgical injury to the surrounding health tissues, the cryoprobe localization for each specific tumor is critical. We developed finite difference analysis to calculate the freezing process during cryosurgery. According to our experimental data, the simulation results from the Pennes equation coupled with immersion boundary method (IBM) are consistent with the experimental data, with a maximum error of ±8.12%.We further incorporate a genetic algorithm as a planning tool to address the problem in connection to be interactive positioning of the cryoprobes and the freezing process duration during the pre-operative stage. Several optimization scenarios are judiciously investigated to emphasize different performance variables. Key results have revealed that this computerized approach is highly efficient one for selecting optimized multiple operational parameters.
       
  • Droplet on oil impregnated surface: Temperature and velocity fields
    • Abstract: Publication date: December 2019Source: International Journal of Thermal Sciences, Volume 146Author(s): Abdullah Al-Sharafi, Bekir Sami Yilbas, Ghassan Hassan The water droplet dynamics on silicon oil impregnated polydimethylsiloxane (PDMS) replicated and inclined surface is considered and the droplet sliding velocity incorporating force and energy balance is formulated. Since silicon oil film is kept at 308 K and water droplet temperature is initially at 300 K, the droplet heat transfer due to temperature disturbance is examined during droplet sliding. Velocity and temperature fields are computed using the experimental conditions. The droplet sliding velocity resulted from the analytical formulation is compared with the high-speed camera data. In addition, the predictions of the droplet surface temperature are validated with the thermal camera data. The findings reveal that the droplet sliding velocity obtained from the analytical formulation is in agreement with the high-speed camera data. The predictions of droplet temperature also agree well with the thermal camera data. Droplet heat transfer results in two contour rotating circulating structures in the droplet, which contribute to convection heat transfer in the droplet fluid. Silicon oil cloaking on water droplet surface alters the heating rates and flow structure in the droplet. As the distance along the silicon oil surface increases, a unique circulation structure is developed inside the droplet, which enhances the Nusselt and the Bond numbers. Formation of a single circulation is attributed to increased silicon oil ridge height in the frontal region of the droplet.
       
 
 
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