Effect of parameters on the melting performance of triplex tube heat exchanger incorporating phase change material

Abstract

In this study, a two-dimensional mathematical model of a phase change material (PCM) melting in a triplex tube heat exchanger (TTHX) unit was developed. Based on two parameters, exergy efficiency and heat storage rate, the effects of the operating conditions and unit configurations on the thermal storage performance of the investigated TTHX unit were numerically studied. The results indicate that the increase in heat transfer fluid (HTF) inlet temperature improves the heat storage rate but reduces the exergy efficiency. The HTF mass flow rate in the inner and outer tubes should be minimized under the premise that the flow states in both tubes are turbulent. If the flow states in both tubes are turbulent and the HTF mass flow rate remains unchanged, then the HTF mass flow rate in the inner tube should be decreased for higher exergy efficiency. When the PCM radius varies from 30 mm to 70 mm under the same operating conditions, the exergy efficiency increased by 15.6%, while the heat storage rate decreased by 36.8%. If the HTF mass flow rate is large, the variation in TTHX length has a slight influence on the exergy efficiency, but it significantly affects the heat storage rate.