Performance and optimisation of a novel phase change thermal storage device

Abstract

To apply phase-change thermal storage in heat-pump systems, a low heat-transfer temperature difference is required. The typical temperature material requirements for phase change limit the application of its thermal storage in heat pump energy supply systems. This study introduces a novel phase-change thermal storage device suitable for a renewable energy supply system composed of multichannel flat tubes and closed rectangular fins. Performance experiments and optimisation of the connection geometry of the thermal storage units under low heat-transfer temperature differences were carried out. When the inlet temperature of the heat transfer fluid was 55 °C (the melting point of the phase change material is 50 °C), the energy storage density and gravimetric specific power can reach 175.16 kJ/kg and 27.93 W/kg respectively, which has obvious advantages compared to relevant devices in the literature. A dimensionless energy-efficiency ratio was used to optimise the device. It was shown that the series type can significantly increase pressure loss while improving heat storage performance, and optimising the structure and operation design parameters of parallel components is more beneficial in terms of device performance improvement. The optimal operating flow corresponding to different heights of the novel thermal storage unit in parallel was provided, thus laying a theoretical foundation for practical applications.