Simulation of Optical Performance for a Solar Cavity Receiver Arranged With Spiral Tubes

Using TracePro optical software, the differences in optical performance of solar cavity receivers with or without spiral tubes were simulated, and the effects of the reflectivity of inner wall of cavity and the outer diameter and pitch of the spiral tubes on the optical performance of receivers were investigated. Besides, the optical performance of four different receiver shapes were also compared. The results show that it is not proper to approximate the inner wall of the receivers as the outer surface of the spiral tubes, because this approximation cannot truly reflect the heat flux absorbed by the spiral tubes. When the pitch is constant, the reflectivity of the inner wall of the cavity is proportional to the amount of heat flux absorbed by the outer surface of the spiral tubes and the optical efficiency of the system. As the reflectivity is less than 0.8, the increase of the pitch can improve the optical performance of the receiver, while the opposite is true when the reflectivity exceeds 0.8. In addition, the truncated-cylindrical receiver has the best optical performance among the four different shapes of receivers, and its optical efficiency can reach as high as 85.42%. This research can provide theoretical guidance for the design and optimization of receivers, and lay a foundation for the analysis of heat transfer performance of receivers.