Multiple-Relaxation-Time Lattice Boltzmann Simulation of Flow and Heat Transfer in Porous Volumetric Solar Receivers

The flow and heat transfer (FHT) in porous volumetric solar receiver was investigated through a double-distributed thermally coupled multiple-relaxation-time (MRT) lattice Boltzmann model (LBM) in this study. The MRT-LBM model was first verified by simulating the FHT in Sierpinski carpet fractal porous media and compared with the results from computational fluid dynamics (CFD). Three typical porous structures in volumetric solar receivers were developed and constructed, and then the FHT in these three porous structures were investigated using the MRT-LBM model. The effects of pore structure, Reynolds (Re) number based on air velocity at inlet, the porosity, and the thermal diffusivity of solid matrix were discussed. It was found that type-III pore structure among the three typical porous structures has the best heat transfer performance because of its lowest maximum temperature of solid particles at the inlet and the highest average temperature of air at the outlet, under the same porosity and heat flux density. Furthermore, increasing the thermal diffusivity of solid particles will lead to higher averaged air temperature at the outlet. It is hoped that the simulation results will be beneficial to the solar thermal community when designing the solar receivers in concentrated solar power (CSP) applications.