THERMAL PERFORMANCE OF STEAM RECEIVER IN TOWER-TYPE SOLAR POWER PLANTS

摘要

In this paper, the thermal performance of steam receiver in tower-type solar power plants has been performed using the tower-type solar receiver design program developed by Shanghai boiler works Co Ltd. In the program, the integrated effect of three types of heat transfer, i.e. heat conduction, convection and radiation, in the process of heat transfer of receivers has been considered. With integrating the characteristics and the working conditions of receivers of both steam and molten salt, the developed program can be used to perform the thermal performance calculations for the receivers of both working fluids. The proposed program was validated through Solar Two project and the satisfactory results achieve. A steam receiver in a tower-type solar power plant with double superheats is selected as an example for thermal performance calculation. In view of the receiver operating in subcritical status, the thermal performance calculation is carried out for two sections, the one for evaporation and that for superheat. In evaporation section, the working fluid is circulated with a circulating pump at a very high circulating ratio. At the outlet of panels, the qualities of working fluid can reach to maximum about 0.35. Besides, the great difference of qualities of working fluid at the outlet of panels is observed. Even for some pipes of some panels, the working fluid at the outlet is in liquid phase. The distribution of metal temperature at fin end of panels in the evaporation region varies dramatically from place to place and reaches to over 520 °C. In superheat region, the temperature of the outer front crown of tubes is concerned. The highest front point temperature of pipe, which reaches to maximum over 660 °C, is in the middle region of the last parts of the primary superheat pass. The thermal efficiency distribution of the receiver, including the evaporation and the superheat regions, are also performed. The results show that the averaged efficiency is about 86%. Besides, the phenomenon of negative thermal efficiency happens in both two regions. That is because the solar incidence cannot compensate the natural heat loss due to incident radiation reflection, the pipe wall infrared radiation and convective heat loss.