Flow and heat transfer simulation in porous volumetric solar receivers by non-orthogonal multiple-relaxation time lattice Boltzmann method

Abstract

Flow behavior and heat transfer (FBHT) process within porous volumetric solar receivers (VSR) were studied numerically by the non-orthogonal Multiple-Relaxation Time Lattice Boltzmann Method (NO-MRT-LBM). Three types of porous structures within VSR were distributed and studied. A non-uniform Gaussian heat influx distribution was adopted to approximate the actual conditions. The effects of pore structure (types 1-3) and heat flux distribution (w) on flow behavior and heat transfer process were studied. It was found that the effect of heat flux distribution on the internal heat transfer process of VSR with different porous structure types was mainly determined by the inlet distribution of solid particles. In type 1 and type 2, the instantaneous temperature growth rate of solid particles increased with decreasing w at the inlet area of the model, thus the maximum temperature, the average temperature of the solid particles within the receiver and the air at the outlet increased rapidly. The average temperature of solid particles and air at the outlet in type 3 both increased with the increase of w. Compared with type 2 and type 3, type 1 showed the best effect of heat transfer when heat flux distribution tended to be uneven, which, however, needs to be reduced to avoid the local temperature becoming excessively large. When heat flux distribution tended to be uniform, type 3 showed better heat transfer performance where any excessive local temperature was eliminated.