Numerical study on Phase-change thermal storage for thermal management of intermittent High-Power devices

Abstract

Latent heat thermal energy storage (LHTES) is an effective approach for the thermal management of intermittent high-power output electronics. The limited heat absorption power due to the low conductivity of phase change material is an urgent problem for LHTES, besides, the thermal resistance at the coolant side also plays an important role in the heat transfer performance enhancement of LHTES. This paper investigates a finned tube heat exchanger with dual-side phase change heat transfer, i.e., LHTES of paraffin RT60 on the fin side and condensation of low-pressure water on the tube side. The proposed model couples the three-dimension enthalpy-porosity model on the fin side with the one-dimension homogeneous flow model on the tube side, yielding the solutions of the dynamic process of the LHTES. The heat-charging power and storage effectiveness of LHTES with single-phase and two-phase heat transfer fluids (HTFs) on the tube side are compared and discussed under different condensation pressures and mass flow rates. Heat transfer on both the fin and tube sides is critical for the LHTES performance, and the use of two-phase HTF on the tube side can enhance the heat-charging power by 210.5 % and raise the storage effectiveness by 33.5 %. The storage effectiveness decreases with the increase of condensation pressure while the mass flux of tube-side HTF does not have an obvious effect on the storage effectiveness. The maximum power density (1.3 kW/L) of LHTES is obtained when the condensing pressure is 90 kPa and the mass flow rate is 0.045 kg/s. It is indicated that dual-side phase change heat transfer to store energy can provide a compact and efficient thermal management solution for intermittent high-power devices. The fin density has more significant effects than fin thickness on the heat transfer at the PCM side of the heat exchanger. The average heat-charging power can be increased by 7.0 % as the fin number increases from 60 to 80.