Thermal analysis of a three-layered radiant porous heat exchanger including fluid flow simulation

Abstract

Based on an effective energy conversion method between flowing gas enthalpy and thermal radiation, a three-layered type of porous heat exchanger (PHE) has been proposed. The PHE has one high temperature (HT) and two heat recovery (HR1 and HR2) sections. In HT section, the enthalpy of gas flow converts to thermal radiation and the opposite process happens in HR1 and HR2. In each section, a 2-D rectangular porous medium which is assumed to be absorbing, emitting and scattering is presented. For theoretical analysis of the PHE, the gas and solid phases are considered in non-local thermal equilibrium and separate energy equations are used for these two phases. Besides, in the gas flow simulation, the Fluent code is used to obtain the velocity distribution in the PHE from inlet to outlet section. For thermal analysis of the PHE, the coupled energy equations for gas and porous layer at each section are numerically solved using the finite difference method. In the computation of radiative heat flux distribution, the radiative transfer equation (RTE) is solved by the discrete ordinates method (DOM). The effects of scattering albedo, optical thickness, particle size of porous medium and inlet gas temperature on the efficiency of PHE are explored. Numerical results show that this type of PHE has high efficiency especially when the porous layers have high optical thickness. The present results are compared with those reported theoretically by other investigators and reasonable agreement is found.

Regularized lattice Bhatnagar–Gross–Krook model for the thermal flow in porous media

“…The problem of flow and heat transfer in the porous media is ubiquitous and of great importance in many fields of science and engineering, such as groundwater, crude oil exploration and extraction, radioactive waste management, improvement of performance of heat transfer systems, hydrogeology, etc. 1–4 There has been many literature issued focusing on such kind of flow using various traditional numerical methods, such as the finite volume (FV) method, the finite difference (FD) method, and the finite element (FE) method. In recent two decades, the lattice Boltzmann (LB) method has evolved into an alternative tool for computational fluid dynamics.…”