Journal•ISSN: 0017-9310
International Journal of Heat and Mass Transfer
Elsevier BV
About: International Journal of Heat and Mass Transfer is an academic journal published by Elsevier BV. The journal publishes majorly in the area(s): Heat transfer & Heat transfer coefficient. It has an ISSN identifier of 0017-9310. Over the lifetime, 29390 publications have been published receiving 1085745 citations.
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TL;DR: In this article, a general, numerical, marching procedure is presented for the calculation of the transport processes in three-dimensional flows characterised by the presence of one coordinate in which physical influences are exerted in only one direction.
Abstract: A general, numerical, marching procedure is presented for the calculation of the transport processes in three-dimensional flows characterised by the presence of one coordinate in which physical influences are exerted in only one direction. Such flows give rise to parabolic differential equations and so can be called three-dimensional parabolic flows. The procedure can be regarded as a boundary-layer method, provided it is recognised that, unlike earlier published methods with this name, it takes full account of the cross-stream diffusion of momentum, etc., and of the pressure variation in the cross-stream plane. The pressure field is determined by: first calculating an intermediate velocity field based on an estimated pressure field; and then obtaining appropriate correction so as to satisfy the continuity equation. To illustrate the procedure, calculations are presented for the developing laminar flow and heat transfer in a square duct with a laterally-moving wall.
5,946 citations
TL;DR: In this article, the local turbulent viscosity is determined from the solution of transport equations for the turbulence kinetic energy and the energy dissipation rate, and the predicted hydrodynamic and heat-transfer development of the boundary layers is in close agreement with the measured behaviour.
Abstract: The paper presents a new model of turbulence in which the local turbulent viscosity is determined from the solution of transport equations for the turbulence kinetic energy and the energy dissipation rate. The major component of this work has been the provision of a suitable form of the model for regions where the turbulence Reynolds number is low. The model has been applied to the prediction of wall boundary-layer flows in which streamwise accelerations are so severe that the boundary layer reverts partially towards laminar. In all cases, the predicted hydrodynamic and heat-transfer development of the boundary layers is in close agreement with the measured behaviour.
3,999 citations
TL;DR: In this article, a model is developed to analyze heat transfer performance of nanofluids inside an enclosure taking into account the solid particle dispersion, where the transport equations are solved numerically using the finite-volume approach along with the alternating direct implicit procedure.
Abstract: Heat transfer enhancement in a two-dimensional enclosure utilizing nanofluids is investigated for various pertinent parameters. A model is developed to analyze heat transfer performance of nanofluids inside an enclosure taking into account the solid particle dispersion. The transport equations are solved numerically using the finite-volume approach along with the alternating direct implicit procedure. Comparisons with previously published work on the basis of special cases are performed and found to be in excellent agreement. The effect of suspended ultrafine metallic nanoparticles on the fluid flow and heat transfer processes within the enclosure is analyzed and effective thermal conductivity enhancement maps are developed for various controlling parameters. In addition, an analysis of variants based on the thermophysical properties of nanofluid is developed and presented. It is shown that the variances within different models have substantial effects on the results. Finally, a heat transfer correlation of the average Nusselt number for various Grashof numbers and volume fractions is presented.
2,560 citations
TL;DR: In this article, the authors proposed two different approaches for deriving heat transfer correlation of the nanofluid, and investigated the mechanism of heat transfer enhancement of the nano-fluid.
Abstract: The nanofluid is a solid–liquid mixture in which metallic or nonmetallic nanoparticles are suspended. The suspended ultrafine particles change transport properties and heat transfer performance of the nanofluid, which exhibits a great potential in enhancing heat transfer. The mechanism of heat transfer enhancement of the nanofluid is investigated. Based on the assumption that the nanofluid behaves more like a fluid rather than a conventional solid–fluid mixture, this article proposes two different approaches for deriving heat transfer correlation of the nanofluid. The effects of transport properties of the nanofluid and thermal dispersion are included.
2,355 citations
TL;DR: In this paper, the authors explore four possible explanations for the anomalous thermal conductivity of nanofluids: Brownian motion of the particles, molecular-level layering of the liquid at the liquid/particle interface, the nature of heat transport in the nanoparticles, and the effects of nanoparticle clustering.
Abstract: Recent measurements on nanofluids have demonstrated that the thermal conductivity increases with decreasing grain size. However, such increases cannot be explained by existing theories. We explore four possible explanations for this anomalous increase: Brownian motion of the particles, molecular-level layering of the liquid at the liquid/particle interface, the nature of heat transport in the nanoparticles, and the effects of nanoparticle clustering. We show that the key factors in understanding thermal properties of nanofluids are the ballistic, rather than diffusive, nature of heat transport in the nanoparticles, combined with direct or fluid-mediated clustering effects that provide paths for rapid heat transport.
2,008 citations