In present work, a cavity receiver with quartz glass cover is presented for the dish concentrating system. The quartz glass cover can separate the receiver cavity from the ambient air and its selective coating layer can intercept the infrared radiation emitted from the inner-surface of the cavity receiver, which greatly reduce the natural convection and surface radiation heat losses. To fundamentally understand this design, a two-dimensional model for the heat transfer process that combines the natural convection and the surface radiation is proposed and developed. The simulation results show that the total heat flux of the covered receiver at 0° inclination is only about 36% of that for uncovered receiver. The model is then used to investigate the effects of various system parameters, such as orientation, temperature and emissivity of inner surface, on the heat transfer and fluid flow performance. It is found that, comparing with the natural convection, the surface radiation is the dominant heat transfer pattern. The orientation has significantly influence the convection heat transfer. However, the surface radiation keeps constant for different inclination angles. In addition, it is also found that the radiation heat transfer is significantly affected by the temperature and emissivity of the inner surface. The increase in the surface temperature and emissivity enhances the surface radiation proportion in the total heat loss. However, for the convection heat loss, it changes little and even decreases as the surface temperature and emissivity increases.
Fuqing Cui;雅玲 何;Zedong Cheng;印实 李