A special type of tube receiver unit for solar thermal power generation towers

摘要

Generating power from solar thermal systems is an effective method for realizing grid-scale dispatchable power generation and replacing conventional energy. The central receiver plays a vital function in the entire power generation system. A special type of tubular receiver was proposed in this study. The proposed receiver was intensively investigated to decrease the tube wall temperature and improve the receiver efficiency and working life. In the proposed design, the panels consist of bayonet tubes instead of circular ones. The new bayonet tube consists of two concentric tubes with different diameters, which are connected by a bayonet end cap. The heat transfer performances of the traditional, inner bayonet, and outer bayonet tubes were compared by establishing a 3D model of the tube. When no boundary heat loss is incurred, the wall temperature of the traditional tube and the molten salt temperature of the outer bayonet tube are the highest among the three. The molten salt and tube wall temperatures of the inner bayonet are the lowest, which is the desired outcome. When the boundary heat loss is considered, the outer wall temperature of the inner bayonet tube is lower than that of the traditional straight one. When the flow rate is 4.4 kg/s, the thermal efficiencies of the straight and inner bayonet tubes are 91.5 % and 96.7%, respectively. When the heat flux is non-uniform, the tube wall temperature is uneven because of the cosine effect of the heating surface. The maximum temperature of the outer wall of the inner bayonet tube is lower than that of the straight one, which indicates that the proposed design is promising in the perspective of thermal efficiency. Further simulations were performed to investigate the influence of flow rate and heat flux variations.