Fluid flow, heat transfer and entropy generation analyses of turbulent forced convection through isotropic porous media using RANS models

Turbulent fluid flow, heat transfer and entropy generation through isotropic porous media were investigated utilizing two RANS models, i.e., RNG k-epsilon and SST k-omega. Circular, longitudinal elliptical and transverse elliptical cross-sectional configurations were analyzed with symmetrical boundary conditions for the upper and lower lines and periodic boundary conditions for the back and front lines. Evaluation of the temperature contours indicated two low-temperature regions behind the solid rods of the transverse elliptical cross-sectional configuration exist. For a given specific normalized pressure gradient, dimensionless turbulence kinetic energy, Nusselt number, and heat transfer efficiency, the RNG k-epsilon model resulted in more reliable results for the dimensionless turbulence kinetic energy at low Reynolds numbers when compared with the SST k-omega model. Using the thermal analysis of the three cross-sectional configurations investigated, the longitudinal elliptical resulted in higher heat transfer efficiencies when compared with the circular and transverse elliptical cross-sectional configurations. When the influence of the turbulence effects were included in the entropy generation rate, a second law of thermodynamics analysis indicated that the longitudinal elliptical cross-sectional configuration resulted in a lower entropy generation rate when compared with the circular and transverse elliptical cross-sectional configurations. Combining the results of the first and second law analyses for the three cross-sectional configurations, it is apparent that isotropic porous media consisting of the longitudinal elliptical cross-sectional configuration can simultaneously result in a high heat transfer efficiency and low entropy generation rate. (C) 2018 Elsevier Ltd. All rights reserved.