E X P E R I M E N T A L S T U D Y O F T H E R M A Lp E R F O R M A N C E O N T H E E N D O T H E R M I C O F H E M I S P H E R I C A L C A V I T Y O F D I S H S O L A R

The solar energy is taken as one of the richest reserves of renewable and clean energy resource, which has broad prospects to take the place of other energies. Solar power generation is a good way to use solar energy high efficiently and on a large scale. The thermal use of solar energy and the photo-voltaic generation are two mian ways currently to research it. No matter by which way, the purpose is to improve the use efficiency according to gathering the solar radiation with low density on the earth surface by means of concentration light. Trough type, tower type and dish type are the main ways of solar concentration presently. Dish type has low start-up loss and high potentiality of the system cost compared with trough type and tower type. And what is more, the photoelectric efficiency could come to 29.4%, which is highest of the three types of system. Therefore, the dish-type solar collector system has become the research hotspot for domestic and foreign scholars. The heat receiver is the core component in the solar collector system, which function is to absorb the solar energy to a maximum extent from the condenser’s reflection and convert it into the heat energy, and then pass the heat energy to the circulating working fluid for further heat utilization. So the performance of heat receiver directly affect the photo thermal conversion efficiency of heat system, and further affect the heat efficiency of the whole heat system. Therefore, the research is carried out on the heat receiver turns out to be significant.According to the experimental test on the temperature field of focal plane of the condenser, the spot shape on the focal plane turns not to be a regular disk type but an irregular shape of approximate ellipse. There is a certain distance between the factual focus and the theoretical focus. Refer to the results of the numerical simulation and the tests of the temperature field for the cavity receiver done by the previous researchers, a semi-spherical cavity receiver is designed in this paper and installed on the focus position of the solar condenser. The experimental results show that the receiver has good thermal property and the solar direct radiation has obvious effect on the thermal power and the thermal efficiency of the solar collector. The thermal power increases with the solar direct radiation increasing, but the thermal efficiency decreases with the solar direct radiation increasing. The increasing of the working medium flow of the heat collector system leads to decreasing of the temperature of the inner wall in the heat receiver. The thermal power and the thermal efficiency increase with the flow increasing, and this kind of influence appears to be evident under the condition of low flow. As the seasons change, if the ambient temperature become lower, the thermal power and the thermal efficiency of the collector improve to some extent. In the late research, the intracavity of the cavity receiver is covered with the selective absorbing coating. According to analyze the comparative statistics, adding the selective absorbing coating contributes to increasing of the thermal power and the thermal efficiency of the collector.A certain amount of experimental researches on the influence of the solar collecting system after ash deposition of the condenser have also been carried out in this paper. According to analyze the comparative statistics, the result shows that the ash deposition on the surface of the condenser leads to decreasing of the temperature of the inner wall in the heat receiver, which reduces the thermal power and the thermal efficiency of the collector evidently.