Impact of using triple adiabatic obstacles on natural convection inside porous cavity under non-darcy flow and local thermal non-equilibrium model

Abstract

This work displays a numerical investigation on free convection inside non-Darcy porous cavity having a vertical triple adiabatic obstacles under conditions of Local thermal non-equilibrium (LTNE). Interesting has been focused on how the obstacles lengths arrangements manipulates the enhancement of free convection. Based on obstacles lengths, seven cases have been tested under large ranges of heat transfer coefficient (0.1 ≤ H ≤ 100), ratio of thermal conductivity (0.1 ≤ Kr ≤ 100), obstacles length (0.25 L ≤ Z ≤ 0.75 L), modified Rayleigh number (200 ≤ Ra* ≤ 1000) and inertia coefficient (10−4 ≤ Fs/Pr* ≤ 10−2). Results indicate that the optimum improvement in Nu can be obtained when using small length of all obstacles or the obstacle length should be set in ascending order. The presence of obstacles reduces the heat transfer as compared to its absence. Therefore, the case that has a minimum obstacles length is advised to be used for applications of porous heat exchangers that involved adiabatic obstacles. A significant improvement in Nu is obtained with rising in Ra*, H and Kr and reducing in Fs/Pr*. The density of LTNE region is extremely reduced with rising in H, Kr and Ra* and reducing in Z and Fs/Pr*. The thermal equilibrium case can be reached when using large values of H and Kr.