Pore scale numerical simulation of heat transfer and flow in porous volumetric solar receivers

Highlights: • Coupled pore scale models based on a structured packed bed are established. • Influence factors of reflection loss and radiation propagation are analyzed. • The pore diameter and porosity have strong impacts on the pressure drop. • A combined packed bed is introduced to design volumetric solar absorbers. - Abstract: Volumetric receivers used in concentrated solar power (CSP) plants consist of porous media and transfer energy to the working fluid passing through after being heated by concentrated solar flux. Pore scale models based on structured packed bed volumetric solar receivers with three packed types are investigated in this work. The Monte Carlo Ray Tracing (MCRT) method is employed to analyze the radiation propagation in the volumetric receiver. Then the absorbed flux is used as the boundary heat source in pore scale models, and the heat transfer and flow in pore scale models are analyzed. The influences of porosity, incident angle and receiver absorptivity on the reflection loss and radiation propagation are analyzed. It is demonstrated that the sphere surface absorptivity has a great influence on the absorption process. Smaller incident angle and higher porosity can promote the radiation propagation. The pore diameter and packed type have strong impacts on the pressure drop, while the inlet velocity greatly affects the temperature distribution. Finally, a hybrid packed bed volumetric solar receiver is introduced to optimize the heat transfer and flow in the receiver.