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1.
Heat Transfer Characteristics of Reciprocating Flows in Channels Partially Filled with Porous Medium
This paper presents the effect of introducing a porous medium on the flow regime and heat transfer of a two-dimensional channel
through which the flow is reciprocating. The channel is discretely heated from above and is insulated in the bottom which
can simulate a cooling mechanism for compact circuit boards. In this ideal geometry, a fully developed reciprocating flow
is established via oscillating pressure gradient. In side boundaries, velocity and temperature are assumed to be periodic.
A certain volume of this channel is occupied by a porous medium which is shown to be an effecting tool for augmentation of
heat transfer. At first, Momentum equations of the domain are solved analytically (Brinkman-extended Darcy model is used for
porous region) and then the energy equation is solved numerically using alternating direction implicit (ADI) method. Finally
a case study is investigated for a high-porous and high-conductive medium (Aluminum alloy T-6201) and the enhancing effect
and optimization criteria are discussed in the result section. 相似文献
2.
A numerical study has been conducted to examine the heat transfer from a metal foam-wrapped solid cylinder in cross-flow.
Effects of the key parameters including the free stream velocity and characteristics of metal foam such as porosity, permeability,
and form drag coefficient on heat and fluid flow are examined. Being a determining factor in pressure drop and heat transfer
increment, the porous layer thickness is changed systematically to observe that there is an optimum layer thickness beyond
which the heat transfer does not improve while the pressure drop continues to increase. This has been verified by the application
of Bejan’s Intersection of Asymptotes method. Results have been compared to those of a finned-tube heat exchanger to observe
much higher heat transfer rate with reasonable excess pressure drop leading to a higher area goodness factor for metal foam-wrapped
cylinder. 相似文献
3.
Transport in Porous Media - The present study presents a comprehensive analysis of effects of porous fins on mixed convection heat transfer in lid-driven square cavities, where the top lid has the... 相似文献
4.
Koch Timo Weishaupt Kilian Müller Johannes Weigand Bernhard Helmig Rainer 《Transport in Porous Media》2021,140(1):107-141
Transport in Porous Media - We present a dual network model to simulate coupled single-phase flow and energy transport in porous media including conditions under which local thermal equilibrium... 相似文献
5.
This paper presents a two-equation analysis on the convection heat transfer in porous media based on the modeling developed by Carbonell and Whitaker (1984). The porous system under consideration is bounded by two parallel walls and heated uniformly from one side surface. The Darcy flow is imposed and the fully developed heat transfer is assumed. General solutions, which take into account the additional convective and conductive terms, are obtained for the temperature fields and the Nusselt number. The detailed studies are presented for the porous systems characterized by consolidated and unconsolidated circular unit cells. The results show that, for the consolidated unit cell case, a prediction without the additional convective term overestimates the heat transfer, while for the unconsolidated unit cell case, this effect is negligible. The additional conductive terms are also examined and found to act conventionally as part of the conductive terms. 相似文献
6.
This article is concerned with the effects of flow and migration of nanoparticles on heat transfer in a straight channel occupied with a porous medium. Investigation of force convective heat transfer of nanofluids in a porous channel has not been considered completely in the literature and this challenge is generally considered to be an open research topic that may require more study. The fully developed flow and steady Darcy?CBrinkman?CForchheimer equation is employed in porous channel. The thermal equilibrium model is assumed between nanofluid and solid phases. It is assumed that the nanoparticles are distributed non-uniformly inside the channel. As a result the volume fraction distribution equation is also coupled with governing equations. The effects of parameters such as Lewis number, Schmidt number, Brownian diffusion, and thermophoresis on the heat transfer are completely studied. The results show that the local Nusselt number is decreased when the Lewis number is increased. It is observed that as the Schmidt number is increased, the wall temperature gradient is decreased and as a consequence the local Nusselt number is decreased. The effects of Lewis number, Schmidt number, and modified diffusivity ratio on the volume fraction distribution are also studied and discussed. 相似文献
7.
Suhil Kiwan 《Transport in Porous Media》2007,67(1):17-29
This work introduces a simple method of analysis to study the performance of porous fins in a natural convection environment.
The method is based on using energy balance and Darcy’s model to formulate the heat transfer equation. The thermal performance
of porous fins is then studied for three types of fins: long fin, finite-length fin with insulated tip and a finite-length
fin with tip exposed to a known convection coefficient. It is found from the analysis that the effect of different design
and operating parameters such as: Ra number, Da number, thermal conductivity ratio, Kr and length thickness ratio on the temperature
distribution along the fin is grouped into one newly defined parameter called S_H. The effect of the variation of S_H on the
porous fin thermal performance is established. The effect of varying the fin length and thermal conductivity ratio on the
heat transfer rate from the fin is investigated and compared with that for a solid fin at certain conditions. It is found
that the heat transfer rate from porous fin could exceed that of a solid fin. It is also found that increasing the fin length
and effective thermal conductivity enhances the heat transfer from the fin up certain limit, where a further increase in these
parameters adds no improvement to the fin performance.
On Leave from Jordan University of Science and Technology, Irbid-Jordan 相似文献
8.
以多孔介质为研究对象,采用整场求解法分析了多孔介质温度场和流场随Ra数的变化.研究结果表明:随着Ra增加,由开始流线均匀分布为一个顺时针大窝,逐渐变化为一个顺时针大窝,一个逆时针小窝;流线出现分叉现象;流线分布在两个窝中间和外侧,即流场在小窝中间剧烈流动而在大窝中央基本上保持静止状态;当Ra很小时,热的传输主要依靠传导作用,随着Ra数逐渐增大,对流作用成为热传输的主要动力;当Ra数小于105时,高温壁面Nu数基本在-110~-17间变化,最大值发生在底部,最大值为17,最小值发生在上部,最小值为-110. 相似文献
9.
10.
Avramenko A. A. Kovetska Y. Y. Shevchuk I. V. Tyrinov A. I. Shevchuk V. I. 《Transport in Porous Media》2019,129(3):673-699
Transport in Porous Media - The paper presents results of a study of forced convection in a vertical flat and circular microchannels incorporating porous medium under slip boundary conditions of... 相似文献
11.
M.Z. SAGHIR M. NEJAD H.H. VAZIRI M.R. ISLAM 《International Journal of Computational Fluid Dynamics》2013,27(4):279-292
While fractured formations are possibly the most important contributors to the production of oil worldwide, modeling fractured formations with rigorous treatments has eluded reservoir engineers in the past. To date, one of the most commonly used fractured reservoir models remains the one that was suggested by Warren and Root nearly four decades ago. In this paper, a new model for fractures embedded in a porous medium is proposed. The model considers the Navier-Stokes equation in the fracture (channel flow) while using the Brinkman equation for the porous medium. Unlike the previous approach, the proposed model does not require the assumption of orthogonality of the fractures (sugar cube assumption) nor does it impose incorrect boundary conditions for the interface between the fracture and the porous medium. Also, the transfer coefficient between the fracture and matrix interface does not need to be specified, unlike the cases for which Darcy's law is used. In order to demonstrate the usefulness of the approach, a two-dimensional model of a fractured formation is developed and numerical simulation runs conducted. The proposed model is derived through a series of finite element modeling runs for various cases using the Navier-Stokes equation in the channel while maintaining the Brinkman equation in the porous medium. Various cases studied include different fracture orientations, fracture frequencies, and thermal and solutal constraints. The usefulness of the proposed model in modeling complex formations is discussed. Finally, a series of numerical runs also provided validity of the proposed model for the cases in which thermal and solutal effects are important. Such a study of double diffusive phenomena, coupled with forced convection, in the context of fractured formations has not been reported before. 相似文献
12.
Many porous media such as rocks have mesoscale inhomogeneities. The characteristic sizes of such inhomogeneities are much larger than the pore size but much less than the characteristic scale of the problem, such as the length of the sample on which measurements are taken. In this paper, we have solved the one-particle problem for depolarization of an ellipsoidal particle located in a porous medium with electrokinetic effect. To calculate the effective physical properties of a porous medium with many ellipsoidal inclusions, we have applied the effective field method. The application of this method allows us to take into account the texture of an inhomogeneous medium. The analysis performed has shown that three effective properties of inhomogeneous media (permeability, electroosmotic coupling coefficient and electrical conductivity) are not completely independent variables. General theory is illustrated by calculations of the effective properties of media containing spherical and spheroidal inclusions. 相似文献
13.
In this paper some considerations are presented about the equations needed to set up a model of the process of heat and mass transfer in porous media. A clear classification is made of the various types of equations used and of their physical meaning. Special attention is paid to the thermodynamic equilibrium equations and to their derivation since they are too often taken for granted. The importance of the various transport mechanisms (of mass and energy) is analyzed and the consequences that can arise when some term is neglected are indicated. 相似文献
14.
The optimization of heat transfer for forced convection in a composite porous channel was studied. We investigated the question where should one place, in the core or in the sheath, the material with high permeability and high-thermal conductivity and where should one place the material with low permeability and low-thermal conductivity, to maximize heat transfer from the walls. We also investigated the optimal heat transfer situation when one has the freedom to vary the relative volumes of the core and the sheath. 相似文献
15.
L. K. Sahoo M. K. Roul R. K. Swain 《Journal of Applied Mechanics and Technical Physics》2017,58(6):1115-1122
Natural convection heat transfer from a vertical isothermal plate with pin fins is numerically studied by solving the Navier–Stokes equations along with the energy equation. The average Nusselt number for the plate with different configurations of pin fins is obtained. The average Nusselt number is found to increase with increasing aspect ratio of the fin and to decrease with increasing angle of fin inclination with respect to the plate. There is only a minor difference between the average Nusselt numbers for in-line and staggered arrangement of fins for the range of parameters studied in the present work. A correlation is developed to predict the average Nusselt number of the plate as a function of fin spacing in the streamwise and spanwise directions, aspect ratio of the fin, and its angle of inclination. 相似文献
16.
M. NEJAD M. Z. SAGHIR M. R. ISLAM 《International Journal of Computational Fluid Dynamics》2013,27(2):157-168
In this paper, thermal diffusion phenomena in a porous cavity are investigated. The Brinkman model, coupled with the energy and the mass balance equations was solved numerically using a finite element techniques. A two-component system was included in the model. Different models were investigated to demonstrate the importance of the Soret effect with the presence of gravity vector. We do not take into consideration the pressure effect in the thermal diffusion. Even with such simplification to the problem, results reveal that the thermal diffusion is important and drives a strong convection. A series of convection cells are observed and steady-state solutions are obtained. Asymmetric solutions are obtained for various cases of dual-porosity porous media. Variations in the gravity vector indicated that the convection patterns, as well as the role of Soret coefficient, are profoundly impacted. Finally, the importance of including thermal diffusion in petroleum reservoir simulation is discussed. 相似文献
17.
18.
The effect of the presence of an isotropic solid matrix on the forced convection heat transfer rate from a flat plate to power-law non- Newtonian fluid-saturated porous medium, has been investigated. Numerical results are presented for the distribution of velocity and temperature profiles within the boundary layer. The effects of the flow index, first-order and second-order resistance on the velocity, and temperature profiles are discussed. The missing wall values of the velocity and thermal functions are tabulated. 相似文献
19.
Fethi Kamışlı 《Transport in Porous Media》2009,80(2):345-371
The flow of an incompressible Newtonian fluid confined in a planar geometry with different wall temperatures filled with a
homogenous and isotropic porous medium is analyzed in terms of determining the unsteady state and steady state velocities,
the temperature and the entropy generation rate as function of the pressure drop, the Darcy number, and the Brinkman number.
The one-dimensional approximate equation in the rectangular Cartesian coordinates governing the flow of a Newtonian fluid
through porous medium is derived by accounting for the order of magnitude of terms as well as accompanying approximations
to the full-blown three-dimensional equations by using scaling arguments. The one-dimensional approximate energy and the entropy
equations with the viscous dissipation consisting of the velocity gradient and the square of velocity are derived by following
the same procedure used in the derivation of velocity expressions. The one-dimensional approximate equations for the velocity,
the temperature, and the entropy generation rate are analytically solved to determine the velocity, the temperature, and the
entropy distributions in the saturated porous medium as functions of the effective process parameters. It is found that the
pressure drop, the Darcy number, and the Brinkman number affect the temperature distribution in the similar way, and besides
the above parameters, the irreversibility distribution ratio also affects the entropy generation rate in the similar way. 相似文献
20.
A numerical study is performed to analyze steady laminar forced convection in a channel in which discrete heat sources covered
with porous material are placed on the bottom wall. Hydrodynamic and heat transfer results are reported. The flow in the porous
medium is modeled using the Darcy–Brinkman–Forchheimer model. A computer program based on control volume method with appropriate
averaging for diffusion coefficient is developed to solve the coupling between solid, fluid, and porous region. The effects
of parameters such as Reynolds number, Prandtl number, inertia coefficient, and thermal conductivity ratio are considered.
The results reveal that the porous cover with high thermal conductivity enhances the heat transfer from the solid blocks significantly
and decreases the maximum temperature on the heated solid blocks. The mean Nusselt number increases with increase of Reynolds
number and Prandtl number, and decrease of inertia coefficient. The pressure drop along the channel increases rapidly with
the increase of Reynolds number. 相似文献