The Efficacy Of Flat-plate Solar Collector During Special States

The collector has direct and important influence on the efficacy of solar heatingsystem. During an especial cold winter or some special conditions, such as leakagestage, the efficacy of solar heating system is not clear and it is necessary to study.The performance parameters in different time are measured when the solarcollector is operated during ordinary time and the measure parameters included thesurface temperatures of the collector, the temperatures of water flowing into andflowing out the heat storage tank and so on. According to the experimental results, thevariation of the cloud thickness has clearer influence than the variation of ambienttemperature on the surface temperatures of the collector during transitional periodbetween the autumn and the winter, and the transitional period between the winter andthe spring. when some special states are set, such as the antifreeze leakage state, Theperformance parameters in different time are measured and the measure parametersincluded the surface temperatures of the collector, the temperatures of water flowinginto and flowing out the heat storage tank and so on. Some comporations between theparameters of normal situation and the parameters of leakage sate are conducted. Withthe increasing of solar irradiance and leakage rate, the difference of the temperaturebetween water flowing into and flowing out the heat storage tank is also increasingclearly. The maximum rate of antifreeze stored in the collector is only8L. The majoringredient of antifreeze is ethylene glycol and the disodium hydrogen phosphate is oftenadded into the antifreeze to avoid the corrosive action on metals. During the experiment,different leakage states are studied. Dring a period of small leakage amount (theweeping rate is28%of the maximum rate of antifreeze) and a period of big leakage amount (the weeping rate is60%of the maximum rate of antifreeze), the performanceof the solar collector is discussed. The studied paramenters include the temperaturesvariation of antifreeze and water. When the leakage amount is small, the heatingefficacy of the collector degrade slowly and the temperature of the hot water decreaseslightly. However, when the leakage amount is small, the heating efficacy of thecollector degrade fastly and the temperature of the hot water decrease significant.It is important to note that during the leakage state, the difference of thetemperature between water flowing into and flowing out the heat storage tank isincreasing clearly, but the amount of the storaged heat is decreasing, which woulddegrade performance of the solar heating system.