Showing papers on "Heat transfer coefficient published in 2015"
TL;DR: Li et al. as mentioned in this paper presented a hybrid thermal lattice Boltzmann (LB) model to simulate thermal multiphase flows with phase change based on an improved pseudopotential LB approach.
262 citations
TL;DR: In this article, a CFD modeling of a horizontal circular tube was presented to investigate the effect of nanofluids on laminar forced convective heat transfer, and the results showed that the proposed mixture model revealed a better agreement with the experimental data.
228 citations
TL;DR: In this article, the effects of wall slip velocity and temperature jump of the nanofluid were studied for the first time by using lattice Boltzmann method, and the results indicated that LBM can be used to simulate forced convection for the nano-fluid micro flows.
Abstract: Laminar forced convection heat transfer of water–Cu nanofluids in a microchannel was studied utilizing the lattice Boltzmann method (LBM). The entering flow was at a lower temperature compared to the microchannel walls. Simulations were performed for nanoparticle volume fractions of 0.00 to 0.04 and slip coefficient from 0.005 to 0.02. The model predictions were found to be in good agreement with earlier studies. The effects of wall slip velocity and temperature jump of the nanofluid were studied for the first time by using lattice Boltzmann method. Streamlines, isotherms, longitudinal variations of Nusselt number, slip velocity and temperature jump as well as velocity and temperature profiles for different cross sections were presented. The results indicate that LBM can be used to simulate forced convection for the nanofluid micro flows. Moreover, the effect of the temperature jump on the heat transfer rate is significant. Also, the results showed that decreasing the values of slip coefficient enhances the convective heat transfer coefficient and consequently the Nusselt number (Nu) but increases the wall slip velocity and temperature jump values.
227 citations
TL;DR: In this paper, the thermal characteristics of a finned heat pipe-assisted latent heat thermal energy storage system are investigated numerically using a transient two-dimensional finite volume based model employing enthalpy-porosity technique.
226 citations
TL;DR: In this article, the Cattaneo-Christov heat flux model is used to investigate the rotating flow of viscoelastic fluid bounded by a stretching surface and the boundary layer equations are first modeled and then reduced to self-similar forms via similarity approach.
Abstract: In this paper Cattaneo-Christov heat flux model is used to investigate the rotating flow of viscoelastic fluid bounded by a stretching surface. This model is a modified version of the classical Fourier’s law that takes into account the interesting aspect of thermal relaxation time. The boundary layer equations are first modeled and then reduced to self-similar forms via similarity approach. Both analytical and numerical solutions are obtained and found in excellent agreement. Our computations reveal that velocity is inversely proportional to the viscoelastic fluid parameter. Further fluid temperature has inverse relationship with the relaxation time for heat flux and with the Prandtl number. Present consideration even in the case of Newtonian fluid does not yet exist in the literature.
217 citations
TL;DR: In this article, the authors summarize the published articles in respect to porosity, permeability (K) and inertia coefficient (Cf) and effective thermal conductivity (keff) for porous media, also on the thermophysical properties of nanofluid and the studies on convection heat transfer in porous media with nanoparticles having dimensions of (1-100) nm.
Abstract: There are two advantages of using porous media. First, its dissipation area is greater than the conventional fins that enhances the heat convection. Second is the irregular motion of the fluid flow around the individual beads which mixes the fluid more effectively. Nanofluids result from the mixtures of base fluid with nanoparticles having dimensions of (1–100) nm, with very high thermal conductivities; as a result, it would be the best convection heat transfer by using two applications together: porous media and nanofluids. This article aims to summarize the published articles in respect to porosity, permeability (K) and inertia coefficient (Cf) and effective thermal conductivity (keff) for porous media, also on the thermophysical properties of nanofluid and the studies on convection heat transfer in porous media with nanofluid.
213 citations
TL;DR: In this article, the influence of functional covalent groups on the thermophysical properties of carbon nanotube base fluid was investigated experimentally, and it was found that increasing Reynolds number, Peclet number or fraction of nanomaterial would improve the heat transfer characteristics of the nanofluid.
195 citations
TL;DR: In this paper, the effects of magnetic field on nanofluid flow, heat, and mass transfer between two horizontal coaxial cylinders are studied using a two-phase model, and the effect of viscous dissipation is also taken into account.
Abstract: In this study, the effects of magnetic field on nanofluid flow, heat, and mass transfer between two horizontal coaxial cylinders are studied using a two-phase model. The effect of viscous dissipation is also taken into account. By using the appropriate transformation for the velocity, temperature, and concentration, the basic equations governing the flow, heat, and mass transfer are reduced to a set of ordinary differential equations. These equations subject to the associated boundary conditions are solved numerically using the fourth-order Runge–Kutta method. The effects of Hartmann number, Reynolds number, Schmidt number, Brownian parameter, thermophoresis parameter, Eckert number, and aspect ratio on flow, heat, and mass transfer are examined. Results show that the Nusselt number has a direct relationship with the aspect ratio and Hartmann number but it has a reverse relationship with the Reynolds number, Schmidt number, Brownian parameter, thermophoresis parameter, and Eckert number.
194 citations
TL;DR: In this paper, the results reported in recent investigations on pool boiling and flow boiling from micro/nanostructured surfaces were included, and a comprehensive overview was provided. But, the results of these studies were limited to the micro and nano scale.
179 citations
TL;DR: In this paper, the authors developed a method to internally preheat lithium-ion batteries at low temperatures with sinusoidal alternating current (AC) using a heat generation rate model in frequency domain based on the equivalent electrical circuit.
173 citations
TL;DR: In this article, the effect of magnetic field on heat transfer of Al 2 O 3 -water nanofluid in a two-dimensional horizontal annulus was investigated using the lattice Boltzmann method.
TL;DR: In this article, the effect of longitudinal fins in a double-pipe heat exchanger containing PCM is examined during charging process, where eight rectangular fins are mounted around the HTF (heat transfer fluid) carrying tube.
TL;DR: In this article, the authors reported measurement of heat generation rate from a Li-ion cell at high discharge rates, up to 9.6C, using measurements of cell temperature and surface heat flux.
TL;DR: An experimental investigation of pool boiling heat transfer on multiscale (micro/nano) functionalized metallic surfaces found that the enhancement of the critical heat flux was directly related to the wetting and wicking ability of the surface which acts to replenish the evaporating liquid and delaycritical heat flux.
TL;DR: In this article, three surfaces were fabricated with sintered porous coatings on: (i) entire microchannel surface (sintered-throughout), (ii) only the fin-tops, and (iii) only channel walls, and their performance with degassed water at atmospheric pressure was experimentally obtained.
TL;DR: In this paper, the effect of different values of shear forces, solid nanoparticles concentration, slip coefficient, and periodic heat flux on the flow and temperature fields as well as heat transfer rate has been evaluated.
TL;DR: In this paper, the effect of the nanoparticles on the enhancement of natural convective heat transfer of nanofluids is discussed, and a new non-dimensional parameter, the enhancement ratio, indicating the ratio of the convective temperature transfer coefficient of the nanoffluid to the base fluid, is introduced.
TL;DR: In this article, the performance of microstructured surfaces in enhancing boiling heat transfer (BHT) and critical heat flux (CHF) was investigated with a set of experiments with thirteen prepared samples: twelve with a micro-structured surface, and one with a bare surface.
TL;DR: In this article, eutectic molten salt was used as the latent thermal energy storage (LTES) medium in solar energy applications, which can be powered by the parabolic-trough solar collector using oil as the heat transfer fluid.
TL;DR: In this article, a review of recent researches on the pool boiling heat transfer behavior of nanofluid is presented, where the authors discuss the effects of various parameters on pool boiling.
TL;DR: In this article, a numerical simulation is used to understand and interpret the complex thermal behavior by presenting the flow field in the current complex corrugation micro-channel heat sink, and the comprehensive performance is evaluated by total thermal resistance and thermal enhancement factor.
TL;DR: In this article, the authors investigated the flow and heat transfer characteristics of Aluminium oxide (Al2O3), silver (Ag) and hybrid (Al 2O3+Ag) nanofluids in a wide rectangular micro-channel.
Abstract: Laminar forced convection flow of nanofluids in a wide rectangular micro-channel has been numerically studied. The present study investigated the flow and heat transfer characteristics of Aluminium oxide (Al2O3), silver (Ag) and hybrid (Al2O3+Ag) nanofluids in a micro-channel. The conduction phenomena of the solid region show a significant effect on the heat transfer characteristics of nanofluid. Hence, the channel is considered with finite thickness on its bottom to accommodate heat source or electronic component and a uniform heat flux is applied to the three sides of the solid region. A two-dimensional conjugate heat transfer homogeneous phase model has been developed and results are reported for different Reynolds numbers. The governing equations are solved by Simplified Marker and Cell (SMAC) algorithm on non-staggered grid using finite volume method. The effects of Reynolds number, pure nanoparticles volume concentration, hybrid nanoparticles mixture volume concentrations and nanoparticles size on the flow and heat transfer characteristics are reported. The results show that the average convective heat transfer coefficient increases with increase in nanoparticles volume concentration and Reynolds number. The nanofluids obtained by dispersing nanoparticles such as Al2O3, Ag and hybrid (Al2O3+Ag) in the base fluid shows a significant enhancement of average convective heat transfer coefficient in comparison with pure water. It is also observed that 3 vol.% hybrid nanofluid (0.6 vol.% Al2O3+2.4 vol.% Ag) shows higher average convective heat transfer coefficient than that of pure water, pure oxide (Al2O3) and pure metallic (Ag) nanofluids. The study presents that hybrid nanofluids are the new class of working fluids with less volume concentration of metallic (Ag) nanoparticles. Moreover, use of hybrid nanofluids at high volume concentration reduces the cost of the working fluid and enhances the heat transfer characteristics in comparison with that of metallic nanofluids. The interface temperature between solid and fluid regions are reported for different nanofluids. The size of the nanoparticle shows significant effect on heat transfer characteristics. The present results are matching with the numerical and experimental results available in the literature.
TL;DR: In this paper, the authors presented the application of hydrophobic polydimethylsiloxane-silica coating for the development of biphilic surfaces that are designed to enhance the heat transfer during boiling.
TL;DR: In this paper, a double-pipe heat exchanger made of corrugated outer and inner tubes was investigated, where both of the inner and outer tubes were made by means of a special machine and the heat transfer coefficient was determined using Wilson plots.
TL;DR: In this paper, a highly instrumented condensation module is used to map detailed axial variations of both wall heat flux and wall temperature, which are used to determine axial variation of the condensation heat transfer coefficient.
TL;DR: In this paper, the performance of a printed circuit heat exchanger with helium as the working fluid operating at the typical temperature of 900°C in a very high temperature reactor is studied.
TL;DR: In this article, the thermal performance of a cylindrical microchannel heat sink was experimentally investigated for potential cooling of electronic devices, which comprised of 86 rectangular microchannels with hydraulic diameter of 560μm assembled into a cylinrical geometry and a number of thermocouples were embedded along the microchannel to provide local temperature measurements.
TL;DR: In this paper, the authors investigated the performance of a microchannel heat sink (MCHS) with converging channels using the finite volume method (FVM) in the laminar regime, where the maximum pressure of the MCHS loop was assumed to be limited due to constructional or operational conditions.
TL;DR: In this paper, the authors present the results of an experimental study on the use of Fe 2 O 3 /Kerosene nanofluid for the copper oscillating heat pipe under the magnetic field.
TL;DR: In this paper, an experimental investigation has been made to compare the flow boiling characteristics of deionized water in three different configurations of microchannels, namely, uniform cross-section, diverging cross-sections and segmented finned channels.