Effect of Position of Upper Connecting Pipe on the Tank on Thermal Performance of Domestic Solar Water Heaters with a Vertical Storage Tank and Flat-plate Collectors

In this paper, the domestic solar water heater with a vertical storage tank and a flat-plate collector, which is commercially available and popular in the market, was experimentally investigated. Firstly, natural circulation experiment platform of flat plate domestic solar water heater was set up. The effect of two different positions of upper connecting pipe on temperature variation in the water tank during the heating stage in the daytime and thermal performances was measured. Through the analysis of test data, the difference of temperature stratification in the water tank with upper connecting pipe at high position and at low position were studied respectively. Also the instantaneous efficiency in 10 minutes was defined and compared. The results showed that there was better temperature stratification in the water tank when it's upper connecting pipe at high position during heating stage. In addition, the instantaneous efficiency of solar water heater, which water tank with upper connecting pipe at high location under the natural circulation condition was superior to the water tank with upper circulation pipe at low position.