Entropy generation of viscous dissipative flow in thermal non-equilibrium porous media with thermal asymmetries

• Effects of thermal asymmetries on convection in porous-medium are studied.
• Exergetic effectiveness of porous media with thermal asymmetries is investigated.
• 2-D temperature, Nusselt number and entropy generation contours are analyzed.
• Significance of viscous dissipation in entropy generation is scrutinized.
• Significance of thermal non-equilibrium in entropy generation is studied.

The effect of thermal asymmetrical boundaries on entropy generation of viscous dissipative flow of forced convection in thermal non-equilibrium porous media is analytically studied. The two-dimensional temperature, Nusselt number and entropy generation contours are analysed comprehensively to provide insights into the underlying physical significance of the effect on entropy generation. By incorporating the effects of viscous dissipation and thermal non-equilibrium, the first-law and second-law characteristics of porous-medium flow are investigated via various pertinent parameters, i.e. heat flux ratio, effective thermal conductivity ratio, Darcy number, Biot number and averaged fluid velocity. For the case of symmetrical wall heat flux, an optimum condition with a high Nusselt number and a low entropy generation is identified at a Darcy number of 10−4, providing an ideal operating condition from the second-law aspect. This type of heat and fluid transport in porous media covers a wide range of engineering applications, involving porous insulation, packed-bed catalytic process in nuclear reactors, filtration transpiration cooling, and modelling of transport phenomena of microchannel heat sinks.