for Journals by Title or ISSN
for Articles by Keywords
help
Journal Cover International Journal of Heat and Mass Transfer
  [SJR: 1.749]   [H-I: 137]   [206 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0017-9310 - ISSN (Online) 0017-9310
   Published by Elsevier Homepage  [3118 journals]
  • Investigation of the through-plane thermal conductivity of polymer
           composites with in-plane oriented hexagonal boron nitride
    • Authors: Chen Pan; Jiaoqiang Zhang; Kaichang Kou; Yu Zhang; Guanglei Wu
      Pages: 1 - 8
      Abstract: Publication date: May 2018
      Source:International Journal of Heat and Mass Transfer, Volume 120
      Author(s): Chen Pan, Jiaoqiang Zhang, Kaichang Kou, Yu Zhang, Guanglei Wu
      As a kind of analogy graphite materials, hexagonal boron nitride (hBN) has been widely used to improve the effective thermal conductivity of polymer composites. Due to their high aspect ratio, hBN platelets tend to orient along the in-plane direction of composites. While the through-plane thermal conductivity of polymer composites with in-plane oriented hBN platelets has been seldom systematically studied. In this work, hBN/PTFE composites are prepared via a cold pressing and sintering method. The orientation of hBN platelets is characterized by scanning electron microscopy and X-ray diffraction. The results indicate that hBN platelets are highly in-plane oriented in PTFE matrix. Theoretical models are successfully used to analyze and predict the effective thermal conductivity of the composites, which suggest that low effective thermal conductivity enhancement efficiency originates from the platelet-shaped filler’s high in-plane orientation.

      PubDate: 2017-12-13T08:26:29Z
      DOI: 10.1016/j.ijheatmasstransfer.2017.12.015
      Issue No: Vol. 120 (2017)
       
  • Study of the wet steam flow in the blade tip rotor linear blade cascade
    • Authors: Sławomir Dykas; Mirosław Majkut; Krystian Smołka; Michał Strozik
      Pages: 9 - 17
      Abstract: Publication date: May 2018
      Source:International Journal of Heat and Mass Transfer, Volume 120
      Author(s): Sławomir Dykas, Mirosław Majkut, Krystian Smołka, Michał Strozik
      Experimental investigations of non-equilibrium spontaneous condensation in transonic steam flows in a linear blade cascade were carried out. The cascade consists of the rotor blades of the low-pressure (LP) steam turbine last stage. The experimental testing facility is a part of a small-scale steam power plant located at the Silesian University of Technology in Gliwice. The steam parameters at the testing facility inlet correspond to the wet steam conditions in a low-pressure steam turbine. Static pressure measurements on the blade surface as well as Schlieren images were used to assess the flow field in the steam turbine rotor tip blade linear cascade for different flow conditions. The experimental results were used to validate an in-house CFD code.

      PubDate: 2017-12-13T08:26:29Z
      DOI: 10.1016/j.ijheatmasstransfer.2017.12.022
      Issue No: Vol. 120 (2017)
       
  • An aerothermal study of the influence of squealer width and height near a
           HP turbine blade
    • Authors: C.B. Senel; H. Maral; L.A. Kavurmacioglu; C. Camci
      Pages: 18 - 32
      Abstract: Publication date: May 2018
      Source:International Journal of Heat and Mass Transfer, Volume 120
      Author(s): C.B. Senel, H. Maral, L.A. Kavurmacioglu, C. Camci
      Highly three-dimensional and complex flow structure within the tip gap of an axial flow turbine is a substantial source of aerodynamic loss and heat transfer due to the interaction between the tip leakage vortex, secondary flows and the main passage flow. Most contemporary shroudless high pressure (HP) turbine designs employ squealer tips for durability, structural, aerodynamic design and heat transfer reasons. The present research deals with the influence of squealer width and height on the aerothermal performance of a HP turbine blade. In this study, four different squealer heights and seven squealer width values are investigated using a computational approach for an axial turbine blade depicting an E3 “Energy Efficient Engine” design. The specific HP turbine airfoil under investigation is identical to the rotor tip profile of the Axial Flow Turbine Research Facility (AFTRF) of the Pennsylvania State University. Numerical calculations are performed by solving the three-dimensional, steady and turbulent form of the Reynolds-Averaged Navier-Stokes (RANS) equations. A two-equation turbulence model, Shear Stress Transport (SST) k-ω is used in the present set of calculations. The current numerical predictions show a very good agreement with the extensive aerodynamic measurements obtained in the nozzle guide vane passages of AFTRF. The results indicate that determining proper squealer width and height is crucial to obtain better aerothermal performance in the form of reduced aerodynamic loss and heat transfer to the tip platform. Extensive numerical analysis within the tip gap reveals that increasing squealer height and reducing squealer width increases cavity volume leading to enlarged vortical structures near the pressure side and suction side of the cavity. Because of this enhanced vortical activity in the tip cavity, a blockage to the incoming pass-over flow is introduced and as a result tip leakage mass flow rate is reduced. While the tip leakage flow rate tends to decrease with increased height and reduced width, there is a strong effect from the squealer width and height combination due to the presence of complex interactions in the tip gap region. From a heat transfer point of view, decreasing squealer width and increasing squealer height noticeably reduces the overall Nu ‾ on the blade tip platform. Nu ‾ on the cavity floor, blade tip and squealer side walls are reduced depending on the increasing height and decreasing width values.
      Graphical abstract image

      PubDate: 2017-12-13T08:26:29Z
      DOI: 10.1016/j.ijheatmasstransfer.2017.12.017
      Issue No: Vol. 120 (2017)
       
  • Thermal performance enhancement of composite phase change materials (PCM)
           using graphene and carbon nanotubes as additives for the potential
           application in lithium-ion power battery
    • Authors: Deqiu Zou; Xianfeng Ma; Xiaoshi Liu; Pengjun Zheng; Yunping Hu
      Pages: 33 - 41
      Abstract: Publication date: May 2018
      Source:International Journal of Heat and Mass Transfer, Volume 120
      Author(s): Deqiu Zou, Xianfeng Ma, Xiaoshi Liu, Pengjun Zheng, Yunping Hu
      To improve the performance of lithium-ion power battery thermal management system, multi-walled carbon nanotubes (MWCNT)-based, graphene-based and MWCNT/graphene-based composite phase change materials (PCM) were prepared and experimentally studied. MWCNT-based and graphene-based composite PCM were studied to obtain the optimal addition amounts which could not only improve thermal conductivity but also restrain a rapid temperature rise in liquid PCM. Based on that, composite PCM with various proportion of graphene and MWCNT have been prepared and characterized under the optimal addition amount. In comparison, results showed that composite PCM at the MWCNT/graphene mass ratio of 3/7 could exhibit the best synergistic enhancement heat transfer effect, which the thermal conductivity was increased by 31.8%, 55.4% and 124% compared to graphene-based composite PCM, MWCNT-based composite PCM and pure PCM respectively. In addition, this composite PCM has the highest increase/decrement rate of temperature which can be shortened by 63.3% and 50.0% compared to pure PCM. Finally, the phase change properties and thermal properties of the MWCNT/graphene-based PCM were compared with those of pure PCM. The composite PCM showed great potential in lithium-ion power battery thermal management.

      PubDate: 2017-12-13T08:26:29Z
      DOI: 10.1016/j.ijheatmasstransfer.2017.12.024
      Issue No: Vol. 120 (2017)
       
  • Experimental and numerical investigations of shaped hole film cooling with
           the influence of endwall cross flow
    • Authors: Yifei Li; Yang Zhang; Xinrong Su; Xin Yuan
      Pages: 42 - 55
      Abstract: Publication date: May 2018
      Source:International Journal of Heat and Mass Transfer, Volume 120
      Author(s): Yifei Li, Yang Zhang, Xinrong Su, Xin Yuan
      In modern aero-engine and gas turbine, the highly loaded turbine leads to strong secondary flow by which the main flow and the film cooling jets are driven from the pressure side to the suction side. As a result, the cross flow has considerable influences on the performance of film cooling jets in the endwall region. In this work, the effects of cross flow on the shaped-hole film cooling performance are investigated both experimentally and numerically. Experimental studies are conducted in a curved channel which simulates the real turbine blade environment with the blowing ratio from 0.5 to 2.5. Numerical studies are also conducted to obtain detailed information about vortical structures. Results show that the cross flow changes the relative position of the two pairs of kidney vortices generated at the outlet of the shaped hole. The negative kidney vortices are stuck to the endwall due to the lift force and they decay faster downstream. The coolant is driven by the cross flow to migrate along the radial pressure gradient direction. And the coolant near the endwall migrates further. The peak value of the cooling effectiveness is suppressed; however, the laterally averaged cooling effectiveness is increased, especially at high blowing ratio. An analytical model describing the flow topology about coolant jets with cross flow is proposed and results from this work may help to understand the film cooling behaviour affected by real complicated flow structures in the engine environment.

      PubDate: 2017-12-13T08:26:29Z
      DOI: 10.1016/j.ijheatmasstransfer.2017.11.150
      Issue No: Vol. 120 (2017)
       
  • Effect of microscale compressibility on apparent porosity and permeability
           in shale gas reservoirs
    • Authors: Guanglong Sheng; Farzam Javadpour; Yuliang Su
      Pages: 56 - 65
      Abstract: Publication date: May 2018
      Source:International Journal of Heat and Mass Transfer, Volume 120
      Author(s): Guanglong Sheng, Farzam Javadpour, Yuliang Su
      The pore network in shale reservoirs comprise of nanoporous organic matter (OM) and micron-size pores in inorganic material (iOM). Accurate gas transport models in shale must include gas slippage, Knudsen diffusion, surface diffusion, and sorption. The change in pore size due to the applied stress could consequently affect gas transport processes. In this study we a compression coefficient to characterize the influence of stress sensitivity on key parameters for gas transport. We consider separate stress response in nanoporous organic matter and iOM because of their different mechanical properties. The effects of compressibility on apparent permeability of OM and iOM are analyzed at different pore sizes, pore pressures and for different gas compositions. Our results show that compressibility has a greater influence on the apparent permeability of iOM than on OM when pore sizes are smaller than 10 nm, whereas compression has similar impact on apparent permeability of both media when pore sizes are larger than 10 nm. With the same effective stress, lower pore pressure results in greater impair in permeability. We conducted a reservoir simulation study using conventional dual-continua model with our developed pressure dependent porosity and permeability to showcase field implication of this study. This work is an important and timely investigation of the development of shale-reservoir-flow simulators.

      PubDate: 2017-12-13T08:26:29Z
      DOI: 10.1016/j.ijheatmasstransfer.2017.12.014
      Issue No: Vol. 120 (2017)
       
  • A combined numerical and experimental study on the forced convection of
           Al2O3-water nanofluid in a circular tube
    • Authors: C.J. Ho; C.Y. Chang; Wei-Mon Yan; Pouria Amani
      Pages: 66 - 75
      Abstract: Publication date: May 2018
      Source:International Journal of Heat and Mass Transfer, Volume 120
      Author(s): C.J. Ho, C.Y. Chang, Wei-Mon Yan, Pouria Amani
      This research investigates the contribution of Al2O3 nanoparticle suspensions on laminar forced convection heat transportation of Al2O3-water nanofluid flowing through a circular tube. In this regard, initially, the variation of the wall and bulk fluid temperatures and the values of local Nusselt numbers are experimentally evaluated along the tube. Next, numerically, the effect of various inlet temperatures from 25 to 50 °C on the important characteristics of the problem under study including pressure drop, Nusselt number and entropy generation are further examined through the constant property and temperature-dependent property modeling. The flow rate of the working fluid was ranged from 24 to 180 cm3/min corresponding Re = 120–2000. The imposed heat flux was 5.51 × 102–1.23 × 104 W/m2. It is found that the addition of nanoparticles leads to the reduction of wall temperature and the enhancement of the Nusselt number, while it also causes an increase in the pressure drop along the tube. The results further reveal that the variable-property simulation provides more accurate predictions. The predicted pressure drop is decreased, and the predicted Nusselt number is increased by considering the temperature dependency of thermophysical properties of the nanofluid.

      PubDate: 2017-12-13T08:26:29Z
      DOI: 10.1016/j.ijheatmasstransfer.2017.12.031
      Issue No: Vol. 120 (2017)
       
  • Practical indicators for assessing the magnitudes of wall radiative flux
           and of coupling effects between radiation and other heat transfer modes on
           the temperature law-of-the wall in turbulent gaseous boundary layers
    • Authors: Y.F. Zhang; R. Vicquelin; O. Gicquel; J. Taine
      Pages: 76 - 85
      Abstract: Publication date: May 2018
      Source:International Journal of Heat and Mass Transfer, Volume 120
      Author(s): Y.F. Zhang, R. Vicquelin, O. Gicquel, J. Taine
      Practical indicators are derived to compare radiative and conductive fluxes and the coupling effects of conduction, convection and radiation in turbulent gaseous boundary layers. A first criterion controlling the weight of wall radiative flux compared to wall conductive flux is introduced to assess the necessity of performing radiation simulation under given flow conditions. A second criterion based on the variation of the non-dimensional temperature due to radiation (scaled in wall units) is also developed to predict whether a wall model accounting for radiation is required when coupling effects become significant. These criteria are built from turbulent channel gaseous flow field simulations for many typical conditions, based on a k- ∊ model, a given turbulent Prandtl number expression and a spectral CK model for radiation. They have been validated from the comparison with corresponding fully-coupled results where turbulent fields are solved numerically with direct numerical simulations and where the radiative energy transfer is solved with a Monte Carlo approach. The obtained criterion results are then presented and thoroughly analyzed on a large set of conditions, which would not have been feasible with direct numerical simulations or large-eddy simulations. The influence of system size, Reynolds number, wall emissivity and pressure is synthesized in 2D contour plots of interest for engineers and researchers to assess the magnitude of radiation effects in wall bounded flows.

      PubDate: 2017-12-13T08:26:29Z
      DOI: 10.1016/j.ijheatmasstransfer.2017.12.026
      Issue No: Vol. 120 (2017)
       
  • Effect of graphite content and heating temperature on carbon pick-up of
           ultra-low-carbon steel from magnesia-carbon refractory using CFD modelling
           
    • Authors: Qiang Wang; Fengsheng Qi; Zhu He; Yawei Li; Guangqiang Li
      Pages: 86 - 94
      Abstract: Publication date: May 2018
      Source:International Journal of Heat and Mass Transfer, Volume 120
      Author(s): Qiang Wang, Fengsheng Qi, Zhu He, Yawei Li, Guangqiang Li
      In order to study the effect of refractory graphite content and heating temperature on carbon pick-up of ultra-low-carbon steel from magnesia-carbon refractory, a transient axisymmetric mathematical model has been established. The momentum, heat and mass transfer between the refractory and the molten steel was modeled by using porous medium. Arrhenius law was employed to define the rate of the carbothermic reduction reaction of the magnesia. Besides, a series of experiments were carried out to verify the model. The results indicate that the carbon content of the molten steel rapidly rises when the refractory graphite content ranges from 3 mass% to 10 mass%, and the carbon pick-up induced by direct dissolution is significantly promoted. The influence of the heating temperature on the carbon content in the molten steel however is negligibly small, and the proportions of the carbon pick-up caused by the direct dissolution and the chemical reaction basically remain the same although the heating temperature increases by 100 K. The effect of the refractory graphite content on the carbon pick-up of the molten steel far outweighs that of the heating temperature.

      PubDate: 2017-12-13T08:26:29Z
      DOI: 10.1016/j.ijheatmasstransfer.2017.12.023
      Issue No: Vol. 120 (2017)
       
  • Intelligent modeling of rheological and thermophysical properties of green
           covalently functionalized graphene nanofluids containing nanoplatelets
    • Authors: Pouria Amani; K. Vajravelu
      Pages: 95 - 105
      Abstract: Publication date: May 2018
      Source:International Journal of Heat and Mass Transfer, Volume 120
      Author(s): Pouria Amani, K. Vajravelu
      Regarding the importance of accurate predictions in industrial applications, this research aims to investigate the ability of artificial neural networks (ANNs) to carry out modeling and multi-criteria optimization of the rheological and thermophysical properties of an environmentally-friendly covalently functionalized nanofluid containing graphene nanoplatelets (CGNPs). In this contribution, different ANN structures are assessed and the NNs with 2-7-1, 2-4-1, 2-7-1 and 2-5-1 structures having a linear transfer function (purelin) and a hyperbolic tangent sigmoid (tansig) transfer function in the output and hidden layer are found to give the least difference between the network outputs and the experimental data for the thermal conductivity, viscosity, specific heat capacity, and density, respectively. Moreover, new correlations for thermal conductivity and viscosity of the nanofluid are proposed and the LASSO (Least Absolute Shrinkage and Selection Operator) and SVM (Support Vector Machine) methods are also presented for comparative purposes. It is observed that all models performed in a very comparable fashion, giving an idea of the easy nature of the problem. So it is recommended to train simple linear models like LASSO or SVM for such problems and perhaps the complex NNs are not necessary in some cases of practical prediction applications such as cooling or heating systems containing nanofluids. Furthermore, finding the optimal conditions is another crucial aspect of engineering problems. In this regard, a multi-criteria optimization of the hydrothermal characteristics of the nanofluid (i.e., to find the optimal cases with highest thermal conductivity and the relatively least viscosity) is conducted using the genetic algorithm coupled with a compromise programming approach.

      PubDate: 2017-12-13T08:26:29Z
      DOI: 10.1016/j.ijheatmasstransfer.2017.12.025
      Issue No: Vol. 120 (2017)
       
  • Comparison of the pseudo-single-phase continuum model and the homogeneous
           single-phase model of nanofluids
    • Authors: H.M. Park
      Pages: 106 - 116
      Abstract: Publication date: May 2018
      Source:International Journal of Heat and Mass Transfer, Volume 120
      Author(s): H.M. Park
      We investigate forced convection of a nanofluid in the entrance region of a cylinder and in the fully-developed region of a coaxial cylinder employing the pseudo-single-phase continuum model and the homogeneous single-phase model. While the homogeneous single-phase model assumes a uniform nanoparticle distribution, the pseudo-single-phase continuum model takes care of nonuniform nanoparticle distribution. There has been controversy regarding the cause of heat transfer enhancement in nanofluids. Whether it is caused solely by the variation of thermophysical properties or the nanoparticle distribution also affect it. This controversy may be resolved employing these two models. It is found that nanoparticles drift from hot wall to cold central region in the entrance region, while they drift from cold inner surface to hot outer surface in the fully-developed coaxial cylinder due to the thermophoresis. The resulting nonuniform distributions of nanoparticles are found to add the heat transfer enhancement slightly. On the other hand, the frictional dissipation increases when the heat transfer rate increases. In a sense, the enhanced heat transfer rate is partly achieved at the expense of a higher energy consumption.

      PubDate: 2017-12-13T08:26:29Z
      DOI: 10.1016/j.ijheatmasstransfer.2017.12.027
      Issue No: Vol. 120 (2017)
       
  • The effect of delta winglet attack angle on the heat transfer performance
           of a flat surface
    • Authors: Hao Wu; David S.-K. Ting; Steve Ray
      Pages: 117 - 126
      Abstract: Publication date: May 2018
      Source:International Journal of Heat and Mass Transfer, Volume 120
      Author(s): Hao Wu, David S.-K. Ting, Steve Ray
      The heat transfer performance of a flat plate behind a 10 mm high (h) and 20 mm long delta winglet was studied at a distance up to 30h in a wind tunnel at a Reynolds number based on h of 6000. The focus was on the role of the attack angle, which was varied from 30 to 60° in 15-degree increments. The bottom side of the flat plate was uniformly heated by condensing steam at 100 °C. Surface thermal imaging results indicated that the peak Nusselt number (Nu) increases with the attack angle, and this augmentation was attributed to the larger share of the transverse vortex at the larger attack angles. Peak Nu dropped sharply in the near wake (X/h < 10), presumably due to the rapid fading of the transverse vortex. It subsequently decreased more gradually and became less sensitive to attack angle farther downstream. This extended heat transfer enhancement was postulated to be caused by the slowly-decaying longitudinal vortices which persisted beyond the studied span. The prevailing longitudinal vortex induced heat transfer enhancement was explained in terms of the detailed flow characteristics scrutinized via a triple hot wire at 20h. The Inflow region, where cooler freestream air was brought into the hot plate, corresponded to the maximum Nu boost; while the Outflow region, where heated air began to leave the hot surface, correlated with the Nu valley. Further analysis revealed Nu relations with the local near-surface streamwise velocity, out-of-plate velocity, and turbulence intensity. The specific heat-flow correlations subtly differed between the Inflow and Outflow regions, and thus also the effect of the winglet attack angle.
      Graphical abstract image

      PubDate: 2017-12-13T08:26:29Z
      DOI: 10.1016/j.ijheatmasstransfer.2017.12.030
      Issue No: Vol. 120 (2017)
       
  • Rainbow schlieren-based investigation of heat transfer mechanisms during
           isolated nucleate pool boiling phenomenon: Effect of superheat levels
    • Authors: Surya Narayan; Atul Srivastava; Suneet Singh
      Pages: 127 - 143
      Abstract: Publication date: May 2018
      Source:International Journal of Heat and Mass Transfer, Volume 120
      Author(s): Surya Narayan, Atul Srivastava, Suneet Singh
      Experimental investigation of various heat transfer mechanisms associated with isolated nucleate pool boiling have been presented. Measurements have been made in a complete non-intrusive manner using rainbow schlieren deflectometry technique. Boiling experiments have been performed for two levels of superheat with the bulk fluid maintained under saturated conditions. The rainbow schlieren images have first been subjected to qualitative interpretation wherein various sub-processes associated with the boiling phenomenon, such as development of thermal boundary layer on the substrate surface, inception of single bubble, growth of the vapor bubble till it departs, and scavenging of the superheat layer following the bubble departure have been discussed. Contributions of individual sub-processes towards the overall heat transfer rates achieved for a given superheat level have been determined through quantitative analysis of the images. Schlieren observations revealed the effect of varying superheat levels on parameters such as bubble diameter and departure time. Detailed heat transfer analysis revealed the dominance of evaporative heating in contributing towards the overall heat transfer rates. On the other hand, the contribution of natural convection from the heated substrate was found to be relatively small. In quantitative terms, the evaporative heating was seen to have an individual contribution as high as ≈66% to the overall heat transfer and ≈88% to the growth of the vapor bubble in the case of superheat level of 7 °C.

      PubDate: 2017-12-13T08:26:29Z
      DOI: 10.1016/j.ijheatmasstransfer.2017.12.005
      Issue No: Vol. 120 (2017)
       
  • Experimental investigation into the impact of density wave oscillations on
           flow boiling system dynamic behavior and stability
    • Authors: Lucas E. O'Neill; Issam Mudawar; Mohammad M. Hasan; Henry K. Nahra; R. Balasubramaniam; Nancy R. Hall; Aubrey Lokey; Jeffery R. Mackey
      Pages: 144 - 166
      Abstract: Publication date: May 2018
      Source:International Journal of Heat and Mass Transfer, Volume 120
      Author(s): Lucas E. O'Neill, Issam Mudawar, Mohammad M. Hasan, Henry K. Nahra, R. Balasubramaniam, Nancy R. Hall, Aubrey Lokey, Jeffery R. Mackey
      In order to better understand and quantify the effect of instabilities in systems utilizing flow boiling heat transfer, the present study explores dynamic results for pressure drop, mass velocity, thermodynamic equilibrium quality, and heated wall temperature to ascertain and analyze the dominant modes in which they oscillate. Flow boiling experiments are conducted for a range of mass velocities with both subcooled and saturated inlet conditions in vertical upflow, vertical downflow, and horizontal flow orientations. High frequency pressure measurements are used to investigate the influence of individual flow loop components (flow boiling module, pump, pre-heater, condenser, etc.) on dynamic behavior of the fluid, with fast Fourier transforms of the same used to provide critical frequency domain information. Conclusions from this analysis are used to isolate instabilities present within the system due to physical interplay between thermodynamic and hydrodynamic effects. Parametric analysis is undertaken to better understand the conditions under which these instabilities form and their impact on system performance. Several prior stability maps are presented, with new stability maps provided to better address contextual trends discovered in the present study.

      PubDate: 2017-12-27T09:09:44Z
      DOI: 10.1016/j.ijheatmasstransfer.2017.12.011
      Issue No: Vol. 120 (2017)
       
  • A distributed enthalpy model for the calculation of humid air condensers
           with long narrow channels using a modified Merkel method
    • Authors: Guilin Liu; Chunxin Yang; Xingjuan Zhang; Peng Ke
      Pages: 167 - 177
      Abstract: Publication date: May 2018
      Source:International Journal of Heat and Mass Transfer, Volume 120
      Author(s): Guilin Liu, Chunxin Yang, Xingjuan Zhang, Peng Ke
      A distributed enthalpy model for flow condensation of humid air in long narrow channels is presented in this paper. The model is based on the Merkel method which treats the simultaneous heat and mass transfer between humid air and wet surfaces, with the condensate interfacial waviness effect modified by several correction methods. Experimental data obtained from condensation tests at constant wall temperature conditions are used to validate the model. Results show that the presented model is capable of predicting the distributions of fluid temperature, specific humidity and condensate flow rate in the channel with adequate accuracy. This distributed enthalpy model is simple for condensation calculations in condensers such as plate-fin heat exchangers.

      PubDate: 2017-12-27T09:09:44Z
      DOI: 10.1016/j.ijheatmasstransfer.2017.12.016
      Issue No: Vol. 120 (2017)
       
  • Cooling tower plume abatement using a coaxial plume structure
    • Authors: Shuo Li; Ali Moradi; Brad Vickers; M.R. Flynn
      Pages: 178 - 193
      Abstract: Publication date: May 2018
      Source:International Journal of Heat and Mass Transfer, Volume 120
      Author(s): Shuo Li, Ali Moradi, Brad Vickers, M.R. Flynn
      The traditional approach of cooling tower plume abatement is supposed to result in an unsaturated, well-mixed plume with a “top-hat” structure in the radial structure, but this is an idealization that is rarely achieved in practice. Meanwhile, previous analyses have shown that there may be an advantage in specifically separating the wet and dry air streams whereby the corresponding plume is of the coaxial variety with dry air enveloping (and thereby shielding) an inner core of wet air. Given that a detailed understanding of the evolution of coaxial plumes is presently lacking, we derive an analytical model of coaxial plumes in the atmosphere, which includes the effects of possible condensation. Of particular concern is to properly parameterize the entrainment (by turbulent engulfment) of fluid from the inner to the outer plume and vice versa. We also present and discuss the two different body force formulations that apply in describing the dynamics of the inner plume. Based on the resulting model predictions, we introduce a so-called resistance factor, which is defined as the ratio of the average non-dimensional velocity to the average relative humidity. In the context of visible plume abatement, the resistance factor so defined specifies the likelihood of fog formation and/or a recirculation of moist air into the plenum chamber. On the basis of this analysis, we can identify the region of the operating-environmental condition parameter space where a coaxial plume might offer advantages over its uniform counterpart.

      PubDate: 2017-12-27T09:09:44Z
      DOI: 10.1016/j.ijheatmasstransfer.2017.12.040
      Issue No: Vol. 120 (2017)
       
  • Numerical simulation of fluid-fluid-solid reactions in porous media
    • Authors: Min Liu; Peyman Mostaghimi
      Pages: 194 - 201
      Abstract: Publication date: May 2018
      Source:International Journal of Heat and Mass Transfer, Volume 120
      Author(s): Min Liu, Peyman Mostaghimi
      We present a numerical model to simulate reactive transport involving homogeneous (fluid-fluid) and heterogeneous reactions (fluid-solid) in porous media. The model includes mass transport, homogeneous reaction, heterogeneous reaction and solid modification. The model is validated by comparing reactive flow in simple geometries with analytical solutions and previously published experimental results. Fluid flow, solute transport, and chemical reactions are simulated directly on 3D images of carbonates. The concentration profiles are analysed for comparison of homogeneous and homogeneous-heterogeneous reactions. A large discrepancy is observed between the concentration profiles of reactants due to the mineral dissolution. The simulation results are also compared with the predictions of reactive transport model with only heterogeneous reactions. In such regimes, mineral dissolution occurs near the inlet. However, with addition of homogeneous reaction, more uniform dissolution is observed in the carbonate. Rock mechanical properties including Young’s modulus and Poisson’s ratio are also compared between the two reaction conditions. The results show that the homogeneous-heterogeneous reaction leads to pore geometries with higher mechanical strength. This work investigates the complex process of chemical reactions in carbonates and improves the understanding of reactive transport in porous media.

      PubDate: 2017-12-27T09:09:44Z
      DOI: 10.1016/j.ijheatmasstransfer.2017.11.141
      Issue No: Vol. 120 (2017)
       
  • Pool boiling heat transfer enhancement with electrowetting
    • Authors: Aritra Sur; Yi Lu; Carmen Pascente; Paul Ruchhoeft; Dong Liu
      Pages: 202 - 217
      Abstract: Publication date: May 2018
      Source:International Journal of Heat and Mass Transfer, Volume 120
      Author(s): Aritra Sur, Yi Lu, Carmen Pascente, Paul Ruchhoeft, Dong Liu
      Electrowetting (EW) has drawn significant research interests in droplet-based microfluidics, and most applications focus on electronic displays, lab-on-a-chip devices and electro-optical switches, etc. This paper presents a new application of EW in enhancing pool boiling heat transfer. The working approach capitalizes on the complimentary roles of hydrophobicity and hydrophilicity played in boiling and takes advantage of the ability of EW to alter the surface wettability dynamically and reversely. In this work, the effects of alternating current EW (ACEW) on the heat transfer characteristics of various boiling regimes, including the onset of nucleate boiling (ONB), fully developed nucleate boiling, and film boiling at critical heat flux (CHF) conditions, are investigated. A synchronized high-speed optical imaging and infrared (IR) thermography approach is taken to obtain simultaneous measurements of the bubble dynamics and the wall temperature and heat flux distributions on the boiling surface. Based on the experimental data, boiling curves are constructed and the boiling heat transfer coefficients (BHTCs) are computed. Comparisons with the boiling characteristics of the baseline surface without ACEW demonstrate the efficacy of ACEW in enhancing the performance of pool boiling heat transfer. Some insights are also offered to understand the physics of the ACEW-enhanced boiling behaviors.

      PubDate: 2017-12-27T09:09:44Z
      DOI: 10.1016/j.ijheatmasstransfer.2017.12.029
      Issue No: Vol. 120 (2017)
       
  • Collision-induced jet-like mixing for droplets of unequal-sizes
    • Authors: Kai Sun; Peng Zhang; Ming Jia; Tianyou Wang
      Pages: 218 - 227
      Abstract: Publication date: May 2018
      Source:International Journal of Heat and Mass Transfer, Volume 120
      Author(s): Kai Sun, Peng Zhang, Ming Jia, Tianyou Wang
      The internal mixing of droplets upon coalescence is of fundamental importance to a number of applications in microfluidics, micro-scale heat and mass transfer, and rocket engine propulsion. Compared to the well-known surface-tension-induced jet-like mixing in the coalescence of inertialess droplets, collision-induced jet-like mixing was observed recently and remains inadequately understood. In the present study, the collision dynamics and internal mixing of droplets of unequal sizes was numerical simulated by using the lattice Boltzmann phase-field method, with emphasis on unraveling the mechanism of the internal jet formation and therefore on exploring strategies to facilitate such a mixing pattern. The results show that the formation of the internal jet requires two synergetic flow motions favoring low Oh number and high We number: the capillary-pressure-driven radial converging flow induced by the crater restoration to detach the spreading smaller droplet from the surface, and the impact-inertia-driven axial motion along the crater surface to drive the penetration of the detached fluid. The jet-like structure was found to correlate with the evolution of a main vortex ring, which is formed by the vorticity generation on the interface during initial impact, and transported into the droplet during subsequent oscillations. However, due to the absence of the bulge retraction that generates a significant amount of vorticity and to the extended duration for the jet formation, the main vortex is much less intensive compared to that formed by the inertialess droplet coalescence and is therefore less capable of inducing obvious vortex-ring structure in the mixing pattern. Further simulations by manipulating the disparity of the droplet sizes and the disparity of the liquid viscosities show that, the collision of a larger droplet with lower viscosity with a smaller droplet with higher viscosity is effective in facilitating jet-like mixing.

      PubDate: 2017-12-27T09:09:44Z
      DOI: 10.1016/j.ijheatmasstransfer.2017.11.154
      Issue No: Vol. 120 (2017)
       
  • Heat and mass transfer in a cylindrical heat pipe with a
           circular-capillary wick under small imposed temperature differences
    • Authors: Pramesh Regmi; Harris Wong
      Pages: 228 - 240
      Abstract: Publication date: May 2018
      Source:International Journal of Heat and Mass Transfer, Volume 120
      Author(s): Pramesh Regmi, Harris Wong
      Heat pipes are efficient in transferring heat and have been applied in various thermal systems. Previous models of heat pipes use the heat rate through the pipe as an input parameter, and therefore lack predictive capabilities. Here, we demonstrate, using a simple heat pipe, that if the evaporation and condensing kinetics are properly modeled, then the heat rate is predicted. We consider a cylindrical heat pipe with the inner wall lined with a circular-capillary wick. The capillaries are filled with a partially wetting liquid, and the center of the pipe is filled with its vapor. Initially, the heat pipe is at temperature T0 and the system is under thermodynamic equilibrium. Then, one end of the pipe is heated to T0 + ΔT, while the other end cooled to T0 − ΔT, and the system reaches a steady state. The equilibrium vapor pressure at the hot end is higher than that at the cold end, and this pressure difference drives a vapor flow. As the vapor moves, the vapor pressure at the hot end drops below the equilibrium vapor pressure which induces continuous evaporation from circular pores on the wick surface. At the cold end, the vapor pressure exceeds the equilibrium vapor pressure so that the vapor condenses and releases the latent heat. The condensate moves back to the hot end through the capillaries in the wick to complete a cycle. We assume that the pore size is infinitesimal compared with the pipe dimensions. Thus, pore-level events can be treated separately from pipe-level events. The evaporation rate in each pore is solved in the limit the evaporation number E → ∞ , and an analytic leading-order solution is obtained, assuming ΔT/T0 ≪ 1. The evaporation rate is incorporated into vapor-flow and energy-balance equations along the pipe. Two dimensionless numbers emerge from these equations: the heat pipe number, H, which is the ratio of heat transfer by vapor flow to conductive heat transfer in the liquid and wall, and the evaporation exponent, S, which controls the evaporation gradient along the pipe. We find that vapor-flow heat transfer dominates in heat pipes and H ≫ S ≫ 1. Under these conditions, the non-dimensionalized heat rate through the insulated pipe is found to be simply S. Analytic solutions are also obtained for the pipe temperature and all the other variables. For maximum evaporative heat transfer, we find an optimal pipe length for fixed pipe cross-sectional dimensions, and an optimal wick thickness for a fixed pipe length. These optimal pipe length and wick thickness can help to improve the design of heat pipes and are found for the first time.

      PubDate: 2017-12-27T09:09:44Z
      DOI: 10.1016/j.ijheatmasstransfer.2017.12.012
      Issue No: Vol. 120 (2017)
       
  • Theory and experiment of contact melting of phase change materials in a
           rectangular cavity at different tilt angles
    • Authors: Jingde Zhao; Jing Zhai; Yihang Lu; Ni Liu
      Pages: 241 - 249
      Abstract: Publication date: May 2018
      Source:International Journal of Heat and Mass Transfer, Volume 120
      Author(s): Jingde Zhao, Jing Zhai, Yihang Lu, Ni Liu
      During the heat transfer of phase change materials in a closed cavity, natural convection and contact melting play important roles in heat transfer enhancement. An improved Nusselt boundary layer model is proposed to describe the contact melting process of phase change material in a rectangular cavity at different tilt angles. A 2-dimensional visualization experimental set for contact melting process of phase change material is put up. The melting process of n-octadecane in a rectangular cavity at 7 different tilt angles (0°, 15°, 30°, 45°, 60°, 75°, 90°) is recorded by digital camera. The liquid fraction, dimensionless height and the total melting time of the phase change materials in the tilted rectangular cavity are obtained through digital image processing mothed. The dimensionless height of solid phase change materials and liquid fraction are consistent with the theoretical solution. And the shortest total melting time is when the tilt angle is 60°.

      PubDate: 2017-12-27T09:09:44Z
      DOI: 10.1016/j.ijheatmasstransfer.2017.12.006
      Issue No: Vol. 120 (2017)
       
  • Influence of Rayleigh number and solid volume fraction in
           particle-dispersed natural convection
    • Authors: Jingchen Gu; Shintaro Takeuchi; Takeo Kajishima
      Pages: 250 - 258
      Abstract: Publication date: May 2018
      Source:International Journal of Heat and Mass Transfer, Volume 120
      Author(s): Jingchen Gu, Shintaro Takeuchi, Takeo Kajishima
      To study the heat transfer in a natural convection under dense particulate condition with finite-size spherical particles of uniform diameter, a direct numerical simulation is conducted. For calculating the momentum-interaction between the particle and fluid, our original immersed solid method is applied. The heat transfer in the particle-dispersed flow is treated in Eulerian way with the interfacial flux decomposition method. The results shows that, with fixing the thermal conductivity ratio (of the solid to the fluid) to be 100, the temporal- and horizontal-average Nusselt number 〈Nu〉 t increases monotonically with solid volume fraction (vf) at Rayleigh number Ra = 104, while 〈Nu〉 t at Ra = 105 exhibits a local maximum at around vf = 40%, although 〈Nu〉 t at Ra = 105 is always larger than that at Ra = 104. The heat flux in the particulate system is decomposed into the contributions by convection and conduction through the particles, fluid and interface, and the result shows that the conduction through the interface is the dominant factor to the vertical heat flux in the media. Through visualization of the heat flux through the particle surface, the importance of directly resolving the local heat conduction within the individual particle and through the interface is highlighted.

      PubDate: 2017-12-27T09:09:44Z
      DOI: 10.1016/j.ijheatmasstransfer.2017.12.020
      Issue No: Vol. 120 (2017)
       
  • The behavior of frost layer growth under conditions favorable for
           desublimation
    • Authors: Jaehwan Lee; Kwan-Soo Lee
      Pages: 259 - 266
      Abstract: Publication date: May 2018
      Source:International Journal of Heat and Mass Transfer, Volume 120
      Author(s): Jaehwan Lee, Kwan-Soo Lee
      The purpose of this study is to understand the behavior of frost layer growth under conditions favorable for desublimation. The frosting experiments were conducted on a horizontal cooling surface. Condensation did not occur at the initial stage of frosting, and feather-shaped frost crystals were formed on the cooling surface. These frost crystals grew one-dimensionally while maintaining their shapes. In addition, the effects of operating conditions (air temperature, air velocity, air absolute humidity, cooling surface temperature) on frost layer growth under the conditions favorable for desublimation were investigated. As the cooling surface temperature decreased, the increase in the amount of frost was insignificant. Additionally, an increase in air velocity increased the frost density but not the thickness of the frost layer.

      PubDate: 2017-12-27T09:09:44Z
      DOI: 10.1016/j.ijheatmasstransfer.2017.12.039
      Issue No: Vol. 120 (2017)
       
  • LBM simulation of unsteady flow and heat transfer from a diamond-shaped
           porous cylinder
    • Authors: T.R. Vijaybabu; K. Anirudh; S. Dhinakaran
      Pages: 267 - 283
      Abstract: Publication date: May 2018
      Source:International Journal of Heat and Mass Transfer, Volume 120
      Author(s): T.R. Vijaybabu, K. Anirudh, S. Dhinakaran
      Incompressible, two-dimensional unsteady flow and heat transfer around a permeable diamond-shaped cylinder placed in an infinite stream of fluid have been numerically analyzed employing D2Q9 lattice model of the lattice Boltzmann method. The variations in hydrodynamic and thermal behaviour of the permeable diamond cylinder have been studied for different values of Darcy numbers ( 10 - 6 ⩽ Da ⩽ 10 - 2 ) and Reynolds numbers ( 50 ⩽ Re ⩽ 150 ). The force term which comprises the effects of linear and nonlinear drag forces of the porous medium (the Darcy-Forchheimer term) is directly coupled with collision equation for flow through the porous zone. Single relaxation parameter (SRT-BGK collision operator) is used to relax the particles towards equilibrium. A comprehensive analysis of the effects of Re and Da values on vortex suppression and wake depletion is presented. In addition, the influence of permeability on thermal enhancement ratio at different surfaces of the porous diamond-shaped cylinder is elucidated. A substantial reduction in vortex strength is witnessed for the same Re with higher permeability. Reduction in drag, suppression of vortex shedding and heat transfer augmentation are seen in the permeably rich cylinder. Correlations for time-averaged mean Nusselt number, valid for the range of parameters considered in the present study, are also provided. Furthermore, a comparative study on thermal dissipation from the permeable square and diamond shaped cylinders is carried out at Re = 50, 100 and 150 at different values of Da. This analogy sheds light on understanding the effect of porous body orientation on heat transfer enrichment, which may be handy while modeling porous medium for different engineering applications.

      PubDate: 2017-12-27T09:09:44Z
      DOI: 10.1016/j.ijheatmasstransfer.2017.11.010
      Issue No: Vol. 120 (2017)
       
  • Direct numerical simulation of flow around a heated/cooled isolated sphere
           up to a Reynolds number of 300 under subsonic to supersonic conditions
    • Authors: Takayuki Nagata; Taku Nonomura; Shun Takahashi; Yusuke Mizuno; Kota Fukuda
      Pages: 284 - 299
      Abstract: Publication date: May 2018
      Source:International Journal of Heat and Mass Transfer, Volume 120
      Author(s): Takayuki Nagata, Taku Nonomura, Shun Takahashi, Yusuke Mizuno, Kota Fukuda
      In this study, an analysis of the flow properties around an isolated sphere under isothermal conditions for flows with high Mach numbers and low Reynolds numbers is conducted via direct numerical simulation (DNS) of the three-dimensional compressible Navier–Stokes equations. The calculations are performed with a boundary-fitted coordinate system. The Reynolds number based on the diameter of the sphere and the freestream quantities is varied from 100 to 300, the freestream Mach number is varied between 0.3 and 2.0, and the temperature ratio between the sphere surface and the freestream is varied between 0.5 and 2.0. We focus on the effects of the Mach number and the temperature ratio on the flow properties. The results show the following characteristics: (1) unsteady vortex shedding from the sphere is promoted (suppressed) when the temperature ratio is less (greater) than unity; (2) the drag coefficient increases with the temperature ratio, but previous drag relations give poor prediction on effect of the temperature ratio on the drag coefficient in the continuum regime; (3) Nusselt number relations proposed in previous studies can be applied if the temperature ratio is close to unity under subsonic conditions; (4) the changes in several flow properties can be characterized by a separation point in the range investigated.

      PubDate: 2017-12-27T09:09:44Z
      DOI: 10.1016/j.ijheatmasstransfer.2017.12.042
      Issue No: Vol. 120 (2017)
       
  • Electron beam irradiation effect on critical heat flux in downward-facing
           flow boiling
    • Authors: Laishun Wang; Nejdet Erkan; Haiguang Gong; Koji Okamoto
      Pages: 300 - 304
      Abstract: Publication date: May 2018
      Source:International Journal of Heat and Mass Transfer, Volume 120
      Author(s): Laishun Wang, Nejdet Erkan, Haiguang Gong, Koji Okamoto
      In previous research on nuclear reactors, the effect of irradiation on heat transfer has rarely been studied. We investigated the electron beam irradiation effect on downward-facing flow boiling heat transfer and critical heat flux. All the critical heat flux values in flow boiling decreased after irradiation, particularly at low doses, whereas heat transfer coefficient almost remained the same. Low dose electron beam irradiation substantially increased the nucleation sites on the heated copper surface, and the critical heat flux was inversely related to the nucleation site density in downward-facing flow boiling.

      PubDate: 2017-12-27T09:09:44Z
      DOI: 10.1016/j.ijheatmasstransfer.2017.12.055
      Issue No: Vol. 120 (2017)
       
  • Experimental study of condensation heat transfer on hydrophobic vertical
           tube
    • Authors: Mattacaud Ramachandralal Rajkumar; Arjunan Praveen; Radhakrishnan Arun Krishnan; Lazarus Godson Asirvatham; Somchai Wongwises
      Pages: 305 - 315
      Abstract: Publication date: May 2018
      Source:International Journal of Heat and Mass Transfer, Volume 120
      Author(s): Mattacaud Ramachandralal Rajkumar, Arjunan Praveen, Radhakrishnan Arun Krishnan, Lazarus Godson Asirvatham, Somchai Wongwises
      Condensation heat transfer on surfaces can be enhanced by altering the surface topography. Surface modification technology can promote dropwise condensation which can exhibit higher heat transfer rate than filmwise condensation. This paper presents experimental data on the condensation of steam on vertical bare copper tubes and lead coated copper tubes for degree of sub-cooling in the range 0.5 °C ≤ ΔT ≤ 20 °C. The chemical texture of the tube surface was altered by coating with lead of thickness 10 µm and the physical texture of the surface was transformed by providing four grooves each having equal depths 0.10 mm, 0.15 mm and 0.30 mm. The condensation heat transfer characteristics of the tube surface is explained based on contact angle hysteresis and sliding velocity of the droplet. The results of the study reveal that for the tubes tested the average condensation heat transfer coefficient decreases with increase in degree of sub-cooling. It is also found that for copper tubes, providing grooves aids condensation heat transfer for the range of sub-cooling. However, for lead coated copper tube with/without grooves the heat transfer performance at ΔT < 2 °C shows marked difference in contrast to ΔT > 2 °C.

      PubDate: 2017-12-27T09:09:44Z
      DOI: 10.1016/j.ijheatmasstransfer.2017.12.019
      Issue No: Vol. 120 (2017)
       
  • Theoretical investigation and experimental verification of a mathematical
           model for counter-flow spray separation tower
    • Authors: Yueming Liu; Jing Yu; Liang Chen; Sumin Jin
      Pages: 316 - 327
      Abstract: Publication date: May 2018
      Source:International Journal of Heat and Mass Transfer, Volume 120
      Author(s): Yueming Liu, Jing Yu, Liang Chen, Sumin Jin
      Despite the fact that the conventional one-dimensional model for counter-flow spray separation tower is advanced in reasonable accuracy as well as time and computational resources saving, it fails to describe the physical processes in details. In this paper, the concept of supersaturated state of the moist air was introduced, then a new sectional one-dimensional model was developed with a detailed derivation. A prototypic apparatus was set up and the reliability of the model was validated by the experimental study. When predicting the outlet solution temperature and outlet moist air wet bulb temperature, the relative errors would be more pronounced with a bigger heat and mass transfer driving potential, but they would not exceed 3.59% and 9.54% respectively under the experimental conditions. The simplifying assumptions, the ignored heat and mass transfer at cyclone region and the measuring errors are mainly blamed for the predicted errors. An in-depth heat and mass transfer investigation was conducted with the help of the validated model by studying the profiles of humidity ratio and moist air dry bulb temperature. The proposed model succeeded in capturing the state transformation of the air flow along the axis of the tower and the effects of the operating parameters on the process profiles are discussed.

      PubDate: 2017-12-27T09:09:44Z
      DOI: 10.1016/j.ijheatmasstransfer.2017.12.034
      Issue No: Vol. 120 (2017)
       
  • Three-dimensional turbulent flow and conjugate heat and mass transfer in a
           cross-flow hollow fiber membrane bundle for seawater desalination
    • Authors: Guo-Pei Li; Li-Zhi Zhang
      Pages: 328 - 341
      Abstract: Publication date: May 2018
      Source:International Journal of Heat and Mass Transfer, Volume 120
      Author(s): Guo-Pei Li, Li-Zhi Zhang
      A cross-flow hollow fiber membrane bundle for humidification (MBH) is used for seawater desalination. Fluid flow and conjugate heat and mass transfer in the bundle are studied by numerically solving the continuity, momentum, energy and concentration equations for air side, water side and membrane side, simultaneously in a conjugated way. Contrary to previous studies which considered only 2D laminar or turbulent flow, in this research the full three-dimensional turbulent flow in air side is modelled with a three-dimensional low-Reynolds-number k-ε turbulence model (3D Low Re k-ε). For comparison, besides the proposed 3D turbulence model, other three previously used models, namely, a 2D Low Re k-ε turbulence model, a 2D laminar model, and a 3D laminar model, are also used to investigate the effects of air side turbulence on fluid flow and heat and mass transfer properties in the bundle under a wide range of Reynolds numbers from 100 to 900. It is found that the 3D turbulence model best predicts the friction factors and Nusselt and Sherwood numbers for various module packing fractions under higher Reynolds numbers above 650. The results are validated by velocity measurement and performance test with a seawater desalination system.
      Graphical abstract image

      PubDate: 2017-12-27T09:09:44Z
      DOI: 10.1016/j.ijheatmasstransfer.2017.12.044
      Issue No: Vol. 120 (2017)
       
  • Heat transfer coefficients for helical components inside an Absorption
           Heat Transformer
    • Authors: N. Demesa; J.A. Hernández; J. Siqueiros; A. Huicochea
      Pages: 342 - 349
      Abstract: Publication date: May 2018
      Source:International Journal of Heat and Mass Transfer, Volume 120
      Author(s): N. Demesa, J.A. Hernández, J. Siqueiros, A. Huicochea
      The evaporator and absorber are relevant components inside an Absorption Heat Transformer, because the refrigerant reaches a high latent heat, which is absorbed by the strong binary mixture at high pressure for obtaining the useful heat. Their heat transfer coefficients influence on the design and performance of an AHT. This paper shows the local and overall heat transfer coefficients for evaporator and absorber, by using experimental tests in a compact AHT of 2 kW, which was designed, built and characterized using only two shells (low and high pressure). Every component was made with nested helical coils and water-lithium bromide solution was used as working solution. The variables considered for this analysis were the heating temperature, the mass flux rate, pressure and concentrations. For the evaporator, an overall heat transfer coefficient of 1227.6 W/m2 K was reached with a heating temperature of 358.2 K. In the absorber, the strong binary mixture influences notoriously for the heat transfer coefficients, where the best result was of 157.2 W/m2 K with a concentrations delta of 6%.

      PubDate: 2017-12-27T09:09:44Z
      DOI: 10.1016/j.ijheatmasstransfer.2017.12.038
      Issue No: Vol. 120 (2017)
       
  • Finite element analysis of self-excited instabilities in a lean premixed
           gas turbine combustor
    • Authors: Seong-Ku Kim; Daesik Kim; Dong Jin Cha
      Pages: 350 - 360
      Abstract: Publication date: May 2018
      Source:International Journal of Heat and Mass Transfer, Volume 120
      Author(s): Seong-Ku Kim, Daesik Kim, Dong Jin Cha
      The present study numerically simulates self-excited instabilities of hydrogen-blended natural gas flames in a lean premixed gas turbine combustor with variable chamber length. In order to effectively predict the thermoacoustic instability within the detailed geometry of the combustor, the Helmholtz equation is discretized with a Galerkin finite element method on a three-dimensional hybrid unstructured mesh. The unsteady heat release rate is modeled with an experimentally measured flame transfer function. The nonlinearity associated with the flame response term is handled with an iterative method, and the large-scale eigenvalue problem is solved by means of the shift-invert method of the ARPACK (ARnoldi PACKage) software. The present Helmholtz solver reproduces the experimentally observed instabilities in terms of the mode frequency and the chamber length range of self-excited pressure oscillations which are significantly affected by the hydrogen enrichment of natural gas fuel. The effects of the acoustic boundary condition and the flame response model on the predictive accuracy are also discussed.

      PubDate: 2017-12-27T09:09:44Z
      DOI: 10.1016/j.ijheatmasstransfer.2017.12.021
      Issue No: Vol. 120 (2017)
       
  • Anisotropic equivalent thermal conductivity model for efficient and
           accurate full-chip-scale numerical simulation of 3D stacked IC
    • Authors: Yudan Pi; Ningyu Wang; Jing Chen; Min Miao; Yufeng Jin; Wei Wang
      Pages: 361 - 378
      Abstract: Publication date: May 2018
      Source:International Journal of Heat and Mass Transfer, Volume 120
      Author(s): Yudan Pi, Ningyu Wang, Jing Chen, Min Miao, Yufeng Jin, Wei Wang
      The complexity of thermal management increases as integrated circuits evolved into 3D architectures. Because of the large variation that exists in the thermal conductivity of materials and the geometrical size of structures in the 3D-stacked IC (3D-SIC) network, the extensive computational costs typically render a full-chip-scale numerical simulation impossible. Thus, this paper proposes a fast and implementable full-chip-scale numerical simulation method for thermal management of 3D-SIC. A compact thermal resistance network, with both lateral and vertical heat dissipations considered, is analyzed to establish an accurate anisotropic equivalent thermal conductivity model. The key heat dissipation component, the high thermal conduction path (HTCP) constructed using through-silicon vias (TSVs), micro-bumps, and Cu wires in the redistribution layer (RDL), is fully analyzed by modeling a compact thermal resistance network. The equivalent thermal conductivity of each stacked layer is extracted in blocks from the network and then applied in a finite element calculation for full-chip-scale numerical simulation. Three partitioning strategies to block each stacked layer are tested. As compared to the results of direct finite element simulation of a small-scale 3D-SIC, the proposed method yields improved simulation accuracy (temperature difference <7.5%) and a considerable computational cost reduction (grid number reduced by >77%). As a demonstration, the temperature distribution of a large-scale 3D-SIC with 306 TSVs and 1647 hotspots is successfully simulated within 82 min by implementing this method using a personal computer (Intel Core i5 6300HQ, 60 GB memory).

      PubDate: 2017-12-27T09:09:44Z
      DOI: 10.1016/j.ijheatmasstransfer.2017.10.044
      Issue No: Vol. 120 (2017)
       
  • Process prediction of selective laser sintering based on heat transfer
           analysis for polyamide composite powders
    • Authors: Xiaoyong Tian; Gang Peng; Mengxue Yan; Shunwen He; Ruijuan Yao
      Pages: 379 - 386
      Abstract: Publication date: May 2018
      Source:International Journal of Heat and Mass Transfer, Volume 120
      Author(s): Xiaoyong Tian, Gang Peng, Mengxue Yan, Shunwen He, Ruijuan Yao
      With the increasing research into selective laser sintering of composite powders, a modified numerical model was introduced to provide appropriate process predictions for the production of different functional composites. This numerical method included an effective volumetric heat source model and an integrated testing procedure, in which the differences of polyamide/carbon fiber (PA/CF) and PA/NaCl composite powders in thermo-physical and optical properties were studied. The unknown variables in the numerical model were all determined by experiments. The simulated temperature distributions of different powder beds exhibited a big difference in the melting depth. Entirely different processing parameters were planned for the two composites according to their simulation results. In the following experiments, highly porous PA derived from PA/NaCl composites had a maximum porosity of 59%. Compared with pure PA, CF reinforced PA showed a dramatic increase of the flexural strength and modulus by a factor of 100% and 380%, respectively. Therefore, the design objectives of two PA composites were both well accomplished. In addition, the experimental investigation became more efficient due to the process prediction. The accuracy of the model was validated by the microstructures of PA/CF and PA/NaCl, which meant this method could be used to provide appropriate process planning for more composites.
      Graphical abstract image

      PubDate: 2017-12-27T09:09:44Z
      DOI: 10.1016/j.ijheatmasstransfer.2017.12.045
      Issue No: Vol. 120 (2017)
       
  • Reproducing kernel particle method for coupled conduction–radiation
           phase-change heat transfer
    • Authors: Jia-Dong Tang; Zhi-Hong He; Han Liu; Shi-Kui Dong; He-Ping Tan
      Pages: 387 - 398
      Abstract: Publication date: May 2018
      Source:International Journal of Heat and Mass Transfer, Volume 120
      Author(s): Jia-Dong Tang, Zhi-Hong He, Han Liu, Shi-Kui Dong, He-Ping Tan
      Interaction between conduction and radiation during the phase-change process within multidimensional participating media was numerically investigated. The solutions were based on the reproducing kernel particle method (RKPM). Test cases were analyzed and compared to results from analytical solutions and other studies to examine the performance of RKPM. Comparisons indicate that the RKPM is stable and accurate. The effect of thermo-optics effect on the phase-change process was carried out with the refractive index increases/decreases linearly with the temperature. The solidification process involving radiation was studied in a 2D enclosure. The effects of different parameters, i.e., extinction coefficients, scattering albedos, conduction-radiation parameters, and latent heat, on the temperature profiles were investigated, and the results show the parameters have significant effects on the solidification process. In addition, the solidification process during convection-radiation cooling was analyzed in a cuboid enclosure with the effect of various phase transition temperature ranges.

      PubDate: 2017-12-27T09:09:44Z
      DOI: 10.1016/j.ijheatmasstransfer.2017.12.058
      Issue No: Vol. 120 (2017)
       
  • Minimum heat flux and minimum film-boiling temperature on a completely
           wettable surface: Effect of the Bond number
    • Authors: Jun-young Kang; Tong Kyun Kim; Gi Cheol Lee; Hyun Sun Park; Moo Hwan Kim
      Pages: 399 - 410
      Abstract: Publication date: May 2018
      Source:International Journal of Heat and Mass Transfer, Volume 120
      Author(s): Jun-young Kang, Tong Kyun Kim, Gi Cheol Lee, Hyun Sun Park, Moo Hwan Kim
      We investigated the effect of Bond number of sphere Bo s and surface super-hydrophilicity at minimum film-boiling temperature T MFB and minimum heat flux q″min using quenching experiment at atmospheric pressure and the saturation temperature of water. In particular, we focused on the vapor-releasing dynamics in film boiling and evaluated the main parameters such as vapor-bubble releasing frequency f b and vapor-bubble departure diameter D b. We selected two sizes of quench sphere (sphere diameter D s = 15 mm and 25 mm) based on critical Bond number Bo C to evaluate the vapor-releasing dynamics depending on the Bo s. The super-hydrophilic surface was prepared by the anodic oxidation on zirconium (Zr-702) sphere. High speed visualization and inverse heat transfer calculation facilitate a qualitative and quantitative analysis of film boiling heat transfer. The surface super-hydrophilicity of the quench sphere increases T MFB and q″min: 12% and 366% increase for D s = 15 mm and 20% and 305% increase for D s = 25 mm, respectively. D b strongly depends on D s and exhibits a relatively weak dependency to the surface super-hydrophilicity. f b is affected by the D s and the surface super-hydrophilicity. The increase in T MFB is explained by the liquid-solid contact in film boiling. The D25-CWS exhibits the large area fraction of liquid-solid contact versus total heat transfer surface compared to the D15-CWS. The increase in q″min is related to minimum frequency of vapor-bubble releasing to sustain the stable liquid-vapor interface f b,min because the large f b,min indicates the fast destabilization of the liquid-vapor interface in film boiling during quenching.

      PubDate: 2017-12-27T09:09:44Z
      DOI: 10.1016/j.ijheatmasstransfer.2017.12.043
      Issue No: Vol. 120 (2017)
       
  • Heat transfer of supercritical water in annuli with spacers
    • Authors: Zhen-xiao Hu; Han-yang Gu
      Pages: 411 - 421
      Abstract: Publication date: May 2018
      Source:International Journal of Heat and Mass Transfer, Volume 120
      Author(s): Zhen-xiao Hu, Han-yang Gu
      Experimental investigations on heat transfer of supercritical water in vertical annular channel equipped with spacers have been carried out at the SWAMUP-II facility in Shanghai Jiao Tong University. The test section consists of a heated outer rod of 15.0 mm inner diameter and a concentric unheated inner rod of 7.41 mm outer diameter. The simplified spacers with blockage ratio of 0.2 and 0.3 are equipped into the annular channel. The water flows upward cooling the heated tube. The pressure and mass flux ranges are 23–25 MPa and 450–1200 kg/(m2·s), respectively. Moreover, the heat flux ranges from 400 to 1000 kW/m2, and the fluid temperature is in the range of 240–450 °C. The heat transfer behaviors downstream from the spacers are analyzed. The effects of seven parameters on the heat transfer enhancement downstream from the spacer are presented. At a certain location downstream from the spacer, the further heat transfer impairment may occur on the basis of the previous deterioration. Conventional heat transfer enhancement prediction methods are compared with the experimental data. The correlations based on the subcritical conditions show the limitations at the supercritical pressure. An improved correlation has been derived.

      PubDate: 2017-12-27T09:09:44Z
      DOI: 10.1016/j.ijheatmasstransfer.2017.12.056
      Issue No: Vol. 120 (2017)
       
  • A time-dependent method for the measurement of mass flow rate of gases in
           microchannels
    • Authors: Ernane Silva; Cesar J. Deschamps; Marcos Rojas-Cárdenas; Christine Barrot-Lattes; Lucien Baldas; Stéphane Colin
      Pages: 422 - 434
      Abstract: Publication date: May 2018
      Source:International Journal of Heat and Mass Transfer, Volume 120
      Author(s): Ernane Silva, Cesar J. Deschamps, Marcos Rojas-Cárdenas, Christine Barrot-Lattes, Lucien Baldas, Stéphane Colin
      Accurate measurement methods are required in the analysis of thermodynamic non-equilibrium effects associated with rarefied gas flows. For example, for the specific case of accommodation coefficients measurements, the quantity of interest is often the mass flow rate along the channel. For this purpose, the following paper presents a new time-dependent version of the well-known constant volume method for the accurate measurement of mass flow rates of gases in microchannels. The technique proposed here is an improvement in respect to the classic technique since it can be used for transient experiments. Moreover, it can be applied to configurations with arbitrary upstream and downstream reservoirs dimensions. Particularly, the proposed method relies on the assumption that the flow conductance varies linearly during the experiments and thus the pressure variations in the reservoirs can be fitted by a well-defined exponential function. Then, the instantaneous mass flow rate through the channel can be determined directly from the pressure fitting coefficients. A great advantage of the time-dependent constant volume method is that the measurements can be obtained from a single experiment for a wide range of rarefaction conditions, since the mean pressure between the reservoirs is allowed to change with time. Moreover, this technique represents a convenient manner to provide raw data of pressure variation with time in the reservoirs and transient mass flow rate in the channel by simply providing the fitting coefficients of the theoretically derived functions. A clear geometric criterion is also presented to determine when such mass flow rate measurements can be considered as quasi-steady, corresponding closely to results obtained under steady conditions, when ideally the channel connects two infinite reservoirs at different pressures. Results for flows of nitrogen through a stainless steel microtube ( L = 92.22 ± 0.01 mm and D = 435.5 ± 3.5 µm) were obtained from 118 independent experiments, provided in this work, using two different experimental setups and three different configurations of the system volumes. As expected, no deviation was observed between all experimental campaigns in terms of the reduced mass flow rate. In addition, all results indicate that nitrogen can be considered completely accommodated at the surface of the microtube used, with α = 0.986 ± 0.019 when the diffuse-specular gas-surface interaction model is adopted and α t = 0.991 ± 0.020 ( α n = 1 ) when the Cercignani-Lampis model is adopted.

      PubDate: 2017-12-27T09:09:44Z
      DOI: 10.1016/j.ijheatmasstransfer.2017.11.147
      Issue No: Vol. 120 (2017)
       
  • Transient pool boiling heat transfer of oxidized and roughened Zircaloy-4
           surfaces during water quenching
    • Authors: Hwasung Yeom; Hangjin Jo; Greg Johnson; Kumar Sridharan; Michael Corradini
      Pages: 435 - 446
      Abstract: Publication date: May 2018
      Source:International Journal of Heat and Mass Transfer, Volume 120
      Author(s): Hwasung Yeom, Hangjin Jo, Greg Johnson, Kumar Sridharan, Michael Corradini
      The sensitivity of surface oxidation and surface roughness to transient pool boiling heat transfer was investigated by performing water quenching experiments of Zircaloy-4 rodlets under increased pressure or subcooled water. The results demonstrated that quenching behavior was notably affected by the surface oxidation and the surface roughness regardless of environmental conditions (saturated water at 0.5 MPa or ΔTsub = 15 K). The minimum film boiling temperature increased with the thickness of surface oxide (3.6 ± 0.2 to 55.6 ± 2.2 µm). Rough surfaces (Ra = 11.4 ± 2.5 µm) showed a large surface heat flux with vigorous vapor generation even in the early stages of quenching. To explain the augmented quenching heat transfer by the surface modifications, a hypothesis that incorporates instantaneous heat transfer during liquid–solid contacts in the stable film boiling regime was proposed. The theoretical model with assumptions elucidated the bubble dynamics of the modified surfaces qualitatively and predicted minimum film boiling points depending on the degree of surface oxidation, which were in good agreement with experimental results. Both surface properties and parameters affecting liquid–solid contact are dominant factors in determining transient pool boiling heat transfer during water quenching.

      PubDate: 2017-12-27T09:09:44Z
      DOI: 10.1016/j.ijheatmasstransfer.2017.12.060
      Issue No: Vol. 120 (2017)
       
  • Analysis of the thermal-mechanical problem in the process of flexible roll
           profile electromagnetic control
    • Authors: Wen-wen Liu; Yan-feng Feng; Jing-na Sun; Feng-shan Du
      Pages: 447 - 457
      Abstract: Publication date: May 2018
      Source:International Journal of Heat and Mass Transfer, Volume 120
      Author(s): Wen-wen Liu, Yan-feng Feng, Jing-na Sun, Feng-shan Du
      Roll profile electromagnetic control technology (RPECT) is a new technology for obtaining flexible roll profile curves. Based on induction heating technology and using the thermally driven and internal constraint mechanism of an electromagnetic stick, the technology cleverly converts the energy of induction heating into a thermal-mechanical hybrid power source, thus greatly improving the degree of roll profile control. However, in the process of roll profile control, during roll heating, the phenomenon of roll uniform temperature may appear, which may affect the roll profile curves. The stability of the roll profile after changing is the core problem addressed by the described technology. Therefore, based on a ∅270 mm × 300 mm roll profile electromagnetic control experimental platform, an electromagnetic-thermal-mechanical coupled axisymmetric model is established by using the finite element software MSC.MARC. The effect of different cooling intensities on the roll temperature and the effect of the roll temperature on the roll profile are analysed through experiments and simulations in the process of cooling after continuous heating and during periodic heating after continuous heating. The results show that roll uniform temperature appears in the roll during roll profile control, which seriously affects the roll profile curves. The phenomenon of roll uniform temperature can be effectively inhibited by controlling the temperature of the electromagnetic stick and establishing a reasonable roll surface cooling intensity, and its effect on the roll profile can be eliminated.

      PubDate: 2017-12-27T09:09:44Z
      DOI: 10.1016/j.ijheatmasstransfer.2017.12.050
      Issue No: Vol. 120 (2017)
       
  • A coupled mathematical model of oxygen transfer in electroslag remelting
           process
    • Authors: Xuechi Huang; Baokuan Li; Zhongqiu Liu
      Pages: 458 - 470
      Abstract: Publication date: May 2018
      Source:International Journal of Heat and Mass Transfer, Volume 120
      Author(s): Xuechi Huang, Baokuan Li, Zhongqiu Liu
      A transient coupled mathematical model was established to study the oxygen transfer in electroslag remelting process. The electromagnetics, multiphase flow, heat transfer, mass transfer and species transport were simulated simultaneously with the aid of the finite volume method. The volume of fluid approach was employed to determine the interfaces among the slag, metal and air. An additionally kinetic and thermodynamic model was proposed to predict the mass transfer rates, which were related to the composition of each phase as well as the temperature. A laboratory experiment was carried out to validate the accuracy of the model. The increase of oxygen content in metal is primarily achieved during the formation of droplet, and the mass transfer process at the slag/metal pool interface also contributes to it. The oxygen in air is absorbed into slag causing a rise in oxygen potential of slag, which significantly affects the oxygen content in metal. With the increasing content of ferrous oxide in slag, the mass fraction of oxygen in the metal pool first increases and then flattens out with time. The maximum calculated oxygen content in the metal pool is about 123.52 ppm during the ESR process.
      Graphical abstract image

      PubDate: 2017-12-27T09:09:44Z
      DOI: 10.1016/j.ijheatmasstransfer.2017.10.088
      Issue No: Vol. 120 (2017)
       
  • Experimental study of the influence of the Prandtl number on the
           convective heat transfer from a square cylinder
    • Authors: Marek Kapitz; Christian Teigeler; Robert Wagner; Christian Helcig; Stefan aus der Wiesche
      Pages: 471 - 480
      Abstract: Publication date: May 2018
      Source:International Journal of Heat and Mass Transfer, Volume 120
      Author(s): Marek Kapitz, Christian Teigeler, Robert Wagner, Christian Helcig, Stefan aus der Wiesche
      A detailed convective heat transfer study was conducted for a square cylinder subjected to uniform air and water streams at various inclination angles using a wind tunnel and a towing tank approach, respectively. Since the same test object was considered for both fluids, the comparison of the air and water heat transfer data enabled an assessment of the influence of the Prandtl number on the convective heat transfer. The reliability of the test apparatus was checked by means of mean heat transfer results obtained for air for which accurate literature data were available. The new results of the present experimental study demonstrated that the classical assumption m = 1/3 for the Prandtl number exponent in heat transfer correlations was only valid in cases where a two-dimensional boundary layer flow governed the convective heat transfer. The classical Prandtl number exponent assumption failed in the case of flow regimes dominated by separation and reattachment. The new experimental data indicated that for such three-dimensional flows virtually higher values should be used for the Prandtl number exponent.

      PubDate: 2017-12-27T09:09:44Z
      DOI: 10.1016/j.ijheatmasstransfer.2017.12.032
      Issue No: Vol. 120 (2017)
       
  • Defrosting behavior and performance on vertical plate for surfaces of
           varying wettability
    • Authors: Hisuk Kim; Guangri Jin; Jaehyeon Jeon; Kwan-Soo Lee; Dong rip Kim
      Pages: 481 - 489
      Abstract: Publication date: May 2018
      Source:International Journal of Heat and Mass Transfer, Volume 120
      Author(s): Hisuk Kim, Guangri Jin, Jaehyeon Jeon, Kwan-Soo Lee, Dong rip Kim
      The defrosting behaviors and performances of super-hydrophilic, bare, and super-hydrophobic surfaces were experimentally investigated along different frost layer densities on a vertical plate. The defrosting behavior can be divided into three types based on the size of the water permeation layer. The defrosting behaviors of bare and super-hydrophilic surfaces were similar, whereas the super-hydrophobic surface behaved differently by allowing the frost layer to be easily removed from its surface. Defrosting performance was evaluated based on defrosting time and water retention ratio. Within the low frost layer density range, defrosting time did not depend on surface characteristics. However, as the density of the frost layer increased, defrosting time increased in the bare and super-hydrophilic surfaces, whereas in the super-hydrophobic surface, that time tended to decrease rather than increase. Water retention ratio was highest on the super-hydrophilic surface and lowest on the super-hydrophobic surface in all frost layer densities. Therefore, the defrosting performance of a super-hydrophobic surface was outstanding over a wide range of frost layer densities.

      PubDate: 2017-12-27T09:09:44Z
      DOI: 10.1016/j.ijheatmasstransfer.2017.12.054
      Issue No: Vol. 120 (2017)
       
  • Effects of variable particle sizes on hydrothermal characteristics of
           nanofluids in a microchannel
    • Authors: Tehmina Ambreen; Man-Hoe Kim
      Pages: 490 - 498
      Abstract: Publication date: May 2018
      Source:International Journal of Heat and Mass Transfer, Volume 120
      Author(s): Tehmina Ambreen, Man-Hoe Kim
      This study investigates the influence of nanoparticle size on the heat transfer and pressure drop characteristics of nanofluids for laminar forced convection in a microchannel subjected to constant heat flux. Aqueous nanofluids containing spherical shaped particle dispersions of Al 2 O 3 and TiO 2 , have been simulated by employing discrete phase model (DPM) for a range of ten particle sizes 20–200 nm. Analysis has been carried out by considering two particle weight concentrations (0.1% and 2%) at Reynolds number of 1000, 1200 and 2000. Results demonstrate that for constant nanofluid compositions and flow conditions, convective heat transfer and friction factor are in inverse association with the particle diameter. With the reduction in particle size, the heat transfer coefficient of nanofluids escalates because of particles’ enhanced effective particle surface area and uniform distribution along the channel radial direction. However, this improvement in heat transfer coefficient is compensated by undesirable increase in pressure drop as a consequence of higher viscosity. The variation in hydrothermal characteristics of nanofluids with particle diameter is more significant at higher particle concentration. The maximum heat transfer and friction factor difference of 11% and 20% respectively has been observed between particle sizes 20 nm and 200 nm for the particle concentration of 2%.

      PubDate: 2017-12-27T09:09:44Z
      DOI: 10.1016/j.ijheatmasstransfer.2017.12.067
      Issue No: Vol. 120 (2017)
       
  • A highly accurate backward-forward algorithm for multi-dimensional
           backward heat conduction problems in fictitious time domains
    • Authors: Yung-Wei Chen
      Pages: 499 - 514
      Abstract: Publication date: May 2018
      Source:International Journal of Heat and Mass Transfer, Volume 120
      Author(s): Yung-Wei Chen
      This paper proposes highly accurate one-step backward-forward algorithms for solving multi-dimensional backward heat conduction problems (BHCPs). The BHCP is renowned for being ill-posed because the solutions are generally unstable and highly dependent on the given data. In this paper, the present algorithm combines algebraic equations with a high-order Lie-group scheme to construct one-step algorithms called the backward fictitious integrate method (BFTIM) and the forward fictitious integrate method (FFTIM). First, the original parabolic equation is transformed into a new parabolic equation of an evolution type by introducing a fictitious time variable. Then, the numerical integration of the discretized algebraic equations must satisfy the constraints of the cone structure, Lie-group and Lie algebra at each fictitious time step. Finally, the algorithms with the minimum fictitious time steps along the manifold of the Lie-group scheme approach the true solution with one step when given an initial guess. In addition, this paper provides a strategy to determine the initial guess, which is the reciprocal relationship of the initial condition (IC) and the final condition (FC). More importantly, the IC and FC can be recovered by the BFTIM and FFTIM according to the relation between the IC and FC, even under large noisy measurement data. Five numerical examples of the BHCP are tested and numerical results demonstrate that the present schemes are more effective and stable. In general, the numerical implementations of the BFTIM and FFTIM are simple and have one-step convergence speeds.

      PubDate: 2017-12-27T09:09:44Z
      DOI: 10.1016/j.ijheatmasstransfer.2017.12.070
      Issue No: Vol. 120 (2017)
       
  • Uncertainty quantification for modeling pulsed laser ablation of aluminum
           considering uncertainty in the temperature-dependent absorption
           coefficient
    • Authors: Yeqing Wang; Getachew K. Befekadu; Hongtao Ding; David W. Hahn
      Pages: 515 - 522
      Abstract: Publication date: May 2018
      Source:International Journal of Heat and Mass Transfer, Volume 120
      Author(s): Yeqing Wang, Getachew K. Befekadu, Hongtao Ding, David W. Hahn
      In this paper, an extension of the result of Wang et al. (“Modeling pulsed laser ablation of aluminum with finite element analysis considering material moving front,” Int. J. Heat & Mass Transfer, 113, 1246–1253, 2017) concerning the problem of uncertainty quantification for pulsed laser ablation (PLA) of aluminum is considered, when the source of uncertainty is due to an inherent randomness of the temperature-dependent absorption coefficient. In particular, we use a generalized polynomial chaos (gPC) method to incorporate the parameter uncertainty for the temperature-dependent absorption coefficient within the representation of the laser heat conduction phenomena. Furthermore, numerical simulation studies for the PLA of aluminum, with nanosecond Nd:YAG 266 nm pulsed laser, that demonstrate the proposed gPC predictions are presented. Finally, a sensitivity study is performed to identify whether small changes in the lower and/or upper parameter values of the absorption coefficient provide the most variance in the thermal and ablation responses.

      PubDate: 2017-12-27T09:09:44Z
      DOI: 10.1016/j.ijheatmasstransfer.2017.12.068
      Issue No: Vol. 120 (2017)
       
  • Modeling heat and mass transfer during ground freezing taking into account
           the salinity of the saturating fluid
    • Authors: A. Rouabhi; E. Jahangir; H. Tounsi
      Pages: 523 - 533
      Abstract: Publication date: May 2018
      Source:International Journal of Heat and Mass Transfer, Volume 120
      Author(s): A. Rouabhi, E. Jahangir, H. Tounsi
      In geotechnical engineering applications, the modeling of artificial ground freezing is primarily aimed at predicting the extent of frozen zone around the cooling sources. This modeling could be more or less complex not only according to the material’s texture and the hydro-geological context but also to the salt concentration of the saturating fluid. Through a thermodynamically consistent framework, a fully coupled heat and mass transfer formulation considering the salinity effect was derived. This formulation was intended to capture the most relevant phenomena of ground freezing encountered in geotechnical applications. Particular attention was given to the phase change problem where appropriate simplifying assumptions were made in order to make the proposed methodology easier to apply in field applications. The proposed approach was validated by means of freezing-thawing laboratory tests, carried out on specimens initially fully saturated with sodium chloride solutions at various concentrations. Good agreement was obtained between the measured and predicted results.

      PubDate: 2017-12-27T09:09:44Z
      DOI: 10.1016/j.ijheatmasstransfer.2017.12.065
      Issue No: Vol. 120 (2017)
       
  • Thermo-hydraulic analysis of multi-row cross-flow heat exchangers
    • Authors: Cheen Su An; Man-Hoe Kim
      Pages: 534 - 539
      Abstract: Publication date: May 2018
      Source:International Journal of Heat and Mass Transfer, Volume 120
      Author(s): Cheen Su An, Man-Hoe Kim
      This paper presents thermal hydraulic analysis of the cross-flow finned tube heat exchangers for an out-door unit in residential air-conditioning and heat pump applications. Performance of heat exchangers affect significantly the system energy efficiency and size of the air-conditioning and heat pumps. The Navier-Stokes equations and the energy equation are solved for the three dimensional computation domain that encompasses multiple rows of the fin-tube heat exchangers. Rather than solving the flow and temperature fields for the outdoor heat exchanger directly, the fin-tube array has been approximated by the porous medium of equivalent permeability, which is estimated from a three dimensional finite volume solution for the periodic fin element. This information is essential and time-effective in carrying out the global flow field calculation which, in turn, provides the face velocity for the microscopic temperature-field calculation of the heat exchanger. The flow field and associated heat transfer for a wide range of face velocity and fin-tube arrangements are examined and the results are presented compared with experimental data. The predicted pressure drop and heat transfer rate for various inlet velocities are in excellent agreement with the measured data.

      PubDate: 2017-12-27T09:09:44Z
      DOI: 10.1016/j.ijheatmasstransfer.2017.12.088
      Issue No: Vol. 120 (2017)
       
  • Rotating frame analysis of radiating and reacting ferro-nanofluid
           considering Joule heating and viscous dissipation
    • Authors: Rakesh Kumar; Ravinder Kumar; Sabir Ali Shehzad; M. Sheikholeslami
      Pages: 540 - 551
      Abstract: Publication date: May 2018
      Source:International Journal of Heat and Mass Transfer, Volume 120
      Author(s): Rakesh Kumar, Ravinder Kumar, Sabir Ali Shehzad, M. Sheikholeslami
      We investigated the role of vibrational rotations and slip conditions at liquid-sheet interface in maintaining the three dimensional flow of ferro-nanoliquid (water-Fe3O4) over a bi-directionally stretchable surface under the influence of magnetic field. It is assumed that chemical reactions prevail between two species A and B whose diffusion coefficients are unequal. Also, mass transfer is considered in the presence of homogeneous and heterogeneous reactions for species A and B . Influences of nonlinear thermal radiation along with viscous dissipation and Joule heating are also invoked into the analysis due to their predominance in the control of heat and mass transfer mechanism. Stability and convergence limitations are verified to ensure the accuracy of results. The outcome due to proposed explicit finite difference scheme is exhibited in the form of figures and tables to illustrate the influence of emerging parameters for two cases namely slip nanofluid (SNF) and no slip nanofluid (NSNF). Results reveal that vibrational rotations and slip at the surface of sheet substantially control flow, and heat and mass transfer phenomena.

      PubDate: 2017-12-27T09:09:44Z
      DOI: 10.1016/j.ijheatmasstransfer.2017.12.069
      Issue No: Vol. 120 (2017)
       
  • Effects of spontaneous nanoparticle adsorption on the bubble-liquid and
           
    • Authors: Yang Yuan; Xiangdong Li; Jiyuan Tu
      Pages: 552 - 567
      Abstract: Publication date: May 2018
      Source:International Journal of Heat and Mass Transfer, Volume 120
      Author(s): Yang Yuan, Xiangdong Li, Jiyuan Tu
      Robust predictive models of dynamic bubbly systems of nanoparticle-liquid mixtures are vital to the design and assessment of relevant industrial systems. Previous attempts to model bubbly flows of dilute nanofluids using the classic two-phase flow models were unsuccessful although the apparent hydrodynamic properties of the dilute nanoparticle-liquid mixtures were only negligibly different to those of their pure base liquids. Emerging studies demonstrated that when bubbles exist in the mixture, nanoparticles tend to spontaneously aggregate at the bubble interface, forming a layer of “colloidal armour” and making the bubble interface partially rigid and less mobile. The colloidal armour also significantly modifies the characteristics of the bubble-liquid and bubble-bubble interactions. Therefore, it was proposed that the key job when developing a predictive model based on classic two-phase flow models is to re-formulate the bubble-liquid and bubble-bubble interactions. However, the adsorption of nanoparticles in dynamic bubbly systems has rarely been studied. The lack of mechanistic understanding has severely hindered the model development. Therefore, this study reviews the common findings yielded from experimental and numerical investigations reported in literature, with the aim to clarify the critical points to address when modelling bubbly flows containing nanoparticles using the classic two-fluid and MUSIG models.

      PubDate: 2017-12-27T09:09:44Z
      DOI: 10.1016/j.ijheatmasstransfer.2017.12.053
      Issue No: Vol. 120 (2017)
       
  • Experimental evidence of the impact of radiation coupling on binary
           scaling applied to shock layer flows
    • Authors: G. de Crombrugghe; O. Chazot; T.J. McIntyre; R. Morgan
      Pages: 568 - 574
      Abstract: Publication date: May 2018
      Source:International Journal of Heat and Mass Transfer, Volume 120
      Author(s): G. de Crombrugghe, O. Chazot, T.J. McIntyre, R. Morgan
      Binary scaling is a similitude law used to study the aerothermodynamics of hypersonic vehicles in ground-based high-enthalpy facilities. It enables the duplication of shock layer flows in the vicinity of the stagnation point, including binary chemistry and nonequilibrium processes, over length scales that are practical for experimental testing. It is built on the assumption of a flow devoid of radiation coupling, which drastically narrows down the envelope of flows for which binary scaling can be used. Indeed, if it is strong enough, radiative heat transfer will cause a substantial amount of energy to leak out of the shock layer to the free-stream and other flow regions. As demonstrated in this paper, the strength of that coupling will increase as the length-scale of the flow increases, impacting other flow properties such as its chemical composition or temperature. The resulting impact on macroscopic features of the flow are for example a reduction of the wall heat flux (both convective and radiative) or of the shock standoff distance. These side impacts are identified with experimental measurements on the shock standoff distance in an expansion tube with CO 2 – N 2 mixture flows representative of the venusian atmosphere over cylinders.

      PubDate: 2017-12-27T09:09:44Z
      DOI: 10.1016/j.ijheatmasstransfer.2017.12.071
      Issue No: Vol. 120 (2017)
       
 
 
JournalTOCs
School of Mathematical and Computer Sciences
Heriot-Watt University
Edinburgh, EH14 4AS, UK
Email: journaltocs@hw.ac.uk
Tel: +00 44 (0)131 4513762
Fax: +00 44 (0)131 4513327
 
Home (Search)
Subjects A-Z
Publishers A-Z
Customise
APIs
Your IP address: 54.167.126.106
 
About JournalTOCs
API
Help
News (blog, publications)
JournalTOCs on Twitter   JournalTOCs on Facebook

JournalTOCs © 2009-2016