Numerical simulations of the solar transmission process for a pressurized volumetric receiver

A three-dimensional optical model for a pressurized volumetric receiver (PVR) is developed and corresponding solar radiation propagation process within the PVR is simulated by the Monte Carlo Ray Tracing (MCRT) method. In the computation, the complicated photon transmission process in the SiC porous absorber is simplified as the transmission process in the statistically homogeneous and isotropic turbid medium. Meanwhile, the non-uniform cylindrical coordinate grid is applied in the statistics of energy distribution, which could greatly reduce the number of cells in the computational grid and time compared with normal uniform grid. Based on the above model, the energy distribution in the irregular macro scale porous absorber is determined and then the effects of system parameters, including the incidence angle, the shape of absorber and the optical property of absorber, on the local heat flux of the absorber are investigated. The results show that, under the given operating condition, the radiation heat flux is mostly concentrated at the top area of the absorber and the maximum heat flux value is up to 2.73 × 109 W m−3, but it quickly decreases in the sideward locations. The incidence angle and a relative narrow shape of absorber are helpful to reduce the maximum heat flux in the absorber. Furthermore, as the ratio of absorption coefficient/extinction coefficient decreases, the absorbed radiation energy distribution is more uniform and the max heat flux in the absorber decreases greatly.