Thermal performance of triplex-tube latent heat storage exchanger: simultaneous heat storage and hot water supply via condensation heat recovery

Abstract

In refrigeration system, refrigerant condensing will release a lot of heat. Using condensation heat from cold storage refrigeration system to provide heat for domestic hot water preparation and industrial hot water supply promotes energy conservation, and latent heat thermal energy storage (LHTES) has unique advantages. Compared with the shell-and-tube heat exchanger, the triplex-tube heat exchanger (TTHE) can achieve simultaneous heat storage and hot water preparation, but few studies have investigated the thermal performance. A mathematical model of TTHE is established by enthalpy method, and the dynamic characteristics has been studied. The results show that liquid sensible heat transfer, latent heat transfer and solid sensible heat transfer are three stages experience in the whole process. The heat storage rate increases and the heat release rate decreases gradually with the opposite trend, but finally reaches to balance with a stable value. The higher the HTF inlet temperature is, the higher the outlet temperature is, but the temperature difference in stable stage is smaller. With the increase of mass flow rate, its effect on heat release gradually weakened. Under the calculation conditions, phase change material with 80 °C transformation temperature for cold storage refrigeration system condensing heat recovery is reasonable.