Heat transfer and entropy generation optimization of forced convection in a porous-saturated duct of rectangular cross-section

We investigate analytically the first and the second law characteristics of fully developed forced convection inside a porous-saturated duct of rectangular cross-section. The Darcy-Brinkman flow model is employed. Three different types of thermal boundary conditions are examined. Expressions for the Nusselt number, the Bejan number, and the dimensionless entropy generation rate are presented in terms of the system parameters. The conclusions of this analytical study will make it possible to compare, evaluate, and optimize alternative rectangular duct design options in terms of heat transfer, pressure drop, and entropy generation. (c) 2006 Elsevier Ltd. All rights reserved

Comments on “Flow, thermal, and entropy generation characteristics inside a porous channel with viscous dissipation” by S. Mahmud and R.A. Fraser [Int. J. Thermal Sciences 44 (2005) 21–32]

Hoomen, Merrikh and Ejlali presents comment on the paper on 'Flow, thermal, and entropy generation characteristics inside a porous channel with viscous dissipation' by S. Mahmud and R.A. Fraser. The paper presents closed form solutions to the velocity and temperature distributions that would be very useful for checking numerical computations. The authors have applied the fluid thermal conductivity kf in all of the equations, that should be replaced by the effective thermal conductivity. They have presented the temperature distribution and the Nusselt number as a function of the Darcy number only, inspite of the fact that Re, Pr, and Ec will affect the temperature profile. The authors have applied a clear-fluid compatible term in the entropy production term that has not been already considered in the thermal energy equation. The reliability of the numerical results is questionable though the authors have applied a previously tested numerical scheme

Theoretical analysis of natural convection in an enclosure filled with disconnected conducting square solid blocks

Two different approaches have been Implemented to interpret the existing data in Merrikh and Lage (2005a, in Pop, Ingham, Transport Phenomena in Porous Media, Elsevier, Oxford) pertinent to the pore-scale simulation of natural convection in a laterally heated square enclosure filled with a fluid bathing discrete, disconnected and conducting solid blocks Mathematical analysis of the problem based on the least squares method leads us to a Nu-Ra correlation with the solid-to-fluid thermal conductivity ratio and the porous medium permeability as the controlling parameters In this study, while the porosity is fixed, the permeability is varied by changing either the block size or the number of blocks Hence, three independent variables N, Ra, and K being the number of blocks, Rayleigh number, and the conductivity ratio between the solid and the fluid, respectively, affect the overall heat transfer process Based on a simplified thermal resistance approach, an alternative correlation is proposed to predict the Nusselt number as a function of the aforementioned parameters Detailed analysis of the results and the expected errors are presente

Analytical solution of forced convection in a duct of rectangular cross-section saturated by a porous medium

A theoretical analysis is presented to investigate fully developed (both thermally and hydrodynamically) forced convection in a duct of rectangular cross-section filled with a hyper-porous medium. The Darcy-Brinkman model for flow through porous media was adopted in the present analysis. A Fourier series type solution is applied to obtain the exact velocity and temperature distribution within the duct. The case of uniform heat flux on the walls, i.e. the H boundary condition in the terminology of Kays and Crawford [1], is treated. Values of the Nusselt number and the friction factor as a function of the aspect ratio, the Darcy number, and the viscosity ratio are reported