Numerical Investigation of the Tube Layout Effects on the Heat Losses of Solar Cavity Receiver

The effects of tube layout on the heat losses of solar cavity receiver were numerically investigated. Two typical tube layouts were analyzed. For the first tube layout, only the active surfaces of cavity were covered with tubes. For the second tube layout, both the active cavity walls and the passive cavity walls were covered with tubes. Besides, the effects of water–steam circulation mode on the heat losses were further studied for the second tube layout. The absorber tubes on passive surfaces were considered as the boiling section for one water–steam circulation mode and as the preheating section for the other one, respectively. The thermal performance of the cavity receiver with each tube layout was evaluated according to the previous calculation model. The results show that the passive surfaces appear to have much lower heat flux than the active ones. However, the temperature of those surfaces can reach a quite high value of about 520 °C in the first tube layout, which causes a large amount of radiative and convective heat losses. By contrast, the temperature of passive surfaces decreases by about 200–300 °C in the second tube layout, which leads to a 38.2–70.3% drop in convective heat loss and a 67.7–87.7% drop in radiative heat loss of the passive surfaces. The thermal efficiency of the receiver can be raised from 82.9% to 87.7% in the present work.