Pore-scale study of gas natural convection in confined porous media based on lattice Boltzmann method

Gas natural convection is one common phenomenon in industrial applications, especially for the thermal management of electronic devices. In this study, a numerical model for gas natural convection in a confined porous cavity is constructed based on the lattice Boltzmann (LB) method, which predicts the density-difference-induced flow using a multiple relaxation time (MRT) collision operator. At the gas-solid interfaces, the microscale flow and heat transfer effects are formulated using an effective slip boundary condition. The established LB model is applied to investigate the Nusselt number for heated obstacles arranged in a staggered formation in the cavity. Based on the calculated data, the Nusselt number values obtained for a five-cylinder pore-scale (single pore, SP) domain are analyzed and compared to those for a 13-cylinder (multipore, MP) one. The Nusselt number shows a sharp decrease as soon as the microscale effect is considered at the obstacle walls. It was also observed that the Nusselt number for MP domain achieved lower values than that of SP one. The findings in this work can contribute to the design of thermal management device with confined porous media.