핀-튜브 열교환기를 갖는 집열기 내 V-그루브 핀에 의한 열교환 성능에 관한 수치해석 연구

Abstract

Solar assisted heat pump is one of solar thermal system that can increase system performance of traditional heat pump. In this system, solar thermal energy obtained from solar collector is used as a heat source for evaporation of refrigerant in heat pump system. Thus the performance of heat pump system can be enhanced by higher evaporating temperature than traditional heat pump without solar collector for same condensing temperature and thermal efficiency of solar collector also can be increased because of the lower operating temperature. But traditional solar assisted heat pump system could not working when the solar radiation is not enough such as cloudy day and at night and extra outdoor unit is needed as evaporator of heat pump system for using air source. Therefore, hybrid solar collector that has fin-and-tube heat exchanger have been developed. This collector has a fin-and-tube heat exchanger under absorbing plate. Thus the collector can get a thermal energy not only from solar energy but also air source when the solar radiation is not enough. At this time, quantity of heat gain is one of important things and it is depend on the structure of fin-and-tube heat exchanger. So, in this study, heat gain from air was investigated by various V-groove fin of fin-and-tube heat exchanger in hybrid solar collector. As a result, heat transfer rate was increased from 18.44% to 48% according to length of V-groove edge than plate type fin. But pressure drop was also increased with increment of heat transfer rate. Thus the JF factor considering both heat transfer rate and pressure drop was also confirmed and higher JF factor was shown when the V-groove width was 4mm different with heat transfer rate. Thus the 4mm V-groove fin was considered as a proper type for applying to real hybrid solar collector. But JF factor can be changed by the other geometric conditions of V-groove fin. Thus, it is also confirmed that optimal geometric condition is need to be found in the further study with more various geometric conditions of V-groove fin.