Experimental Research on a Novel Solar Water Heating System by Using Loop Heat Pipe

Abstract

In this paper, a novel solar water heating system will be proposed by applying the loop heat pipe to a conventional split solar hot water system, which will have the characteristics of high efficiency, low cost, appearance appealing and building integration. Three types of the system, i.e., the system with evacuated tubes, with single flat-plate glazing cover, and without glazing, will be experimentally investigated and compared on the influence to the dynamic performance of the system. It was found that the system’s operating temperature increased significantly during the start-up stage and gently after until reach relatively constant. The instantaneous efficiency was found to be fluctuated, although it reached stable eventually during the operations for all three types. By using the moving average calculating method, every 10 minutes were applied for the calculation of the average efficiency which had a negative linear relation with the combined factor of (Tmean-Tamb)/I. In general, the solar system with evacuated tubes performed the best with the highest water temperature output, highest system efficiency and lowest heat loss coefficient among the three systems.