Effects of plumbing attachments on heat losses from solar domestic hot water storage tanks

Thermal storage tanks are widely applied in most solar domestic water heating systems sold in the United States. Study of the heat loss mechanism of the storage tanks is necessary to develop more accurate tank heat loss models for solar domestic water heater system. Such models will enhance the accuracy of system ratings published by the Solar Rating and Certification Corporation and lead towards improved system efficiency via better design. Previous heat loss studies have shown that the actual losses are about twice the predicted values using {dollar}Q = U cdot A cdot Delta T.{dollar} This thesis addresses heat losses from a residential size solar storage tank. Experiments were designed for two system configurations: a reference tank heat loss with no plumbing attachment, and the tank with typical shaped plumbing attachments. Efforts are made to understand the parameters that affect the overall heat loss of the system. About 200 tank heat loss measurements were completed for six different pipe arrangements under several test conditions.; The salient results were: (1) The stratification and the decay are linear with vertical height and time, respectively. (2) The heat transferred via the pipe fittings and dissipated to ambient is significantly increased when the pipe is filled with water compared to pipe with no water. (3) The heat losses from the plumbing fittings attached to the thermal storage tank are relatively small compared to the heat loss from the tank itself. (4) A thermal heat trap using two U-turns was ineffective in reducing heat losses from plumbing attachments.