Numerical Analysis on Thermal Efficiency of Hybrid Solar Collector with Fin-and-Tube Heat Exchanger

Abstract

A solar assisted heat pump system uses solar thermal energy as a heat source for evaporator in the heat pump by applying solar collector. The COP (coefficient of performance) of the heat pump can be increased when the evaporating temperature increases. The efficiency of the solar collector can be increased because it has lower operating temperature compare to traditional solar collector. Thus, as a part of these researches, a hybrid solar collector that has fin-and-tube heat exchanger has been developed. This collector is flat plat solar collector that can get thermal energy from ambient air for heating the circulating water in the collector by heat exchanging between the air and water side in fin-and-tube heat exchanger. This heated water can be used as heat source of the evaporator in the heat pump even if the solar energy is not enough. So, in this study, an numerical analysis was conducted for confirming the heat gain and pressure drop of water in the collector when the solar energy was provided. As a result, lower thermal efficiency and higher overall heat loss coefficient were obtained when the air channel of the fin-and-tube heat exchanger was opened. But, in case of the closed air channel type, similar maximum thermal efficiency and slightly higher overall heat loss coefficient was obtained. Thus, the significant effect of open and close of the air channel on thermal efficiency was confirmed, and the lower pressure drop of the water side was confirmed with similar thermal efficiency on two row distribution type tube compared to the traditional series type tube. So, it is confirmed that the closed air channel with two row distribution tube can be regarded as proper type.