High-power-density miniaturized packed-bed thermal energy storage unit via phase change material capsules

Miniaturized thermal energy storage (TES) units with phase change materials (PCMs) are promising for the production of portable thermal management devices. In this work, a 100 mm-scale miniaturized packed-bed thermal energy storage (PBTES) unit based on homemade PCM capsules fabricated via the microfluidic method is established. The thermohydrodynamic characteristics of this unit are experimentally studied and analyzed based on a comparison with a traditional shell-and-tube thermal energy storage (STTES) unit. A modified Ergun equation is obtained for predicting the pressure drop of the PBTES unit with good accuracy. The results indicate that with increasing heat transfer fluid (HTF) flow rate, the charging and discharging processes are shorter, and the charging and discharging rates are much higher. The increasing inlet temperature of the HTF produces a large temperature gradient along the axial direction of the PBTES unit and enhances the performance of the PBTES unit. Generally, the average charging rate and overall efficiency of the PBTES unit with an HTF flow rate of 0.5 L/min can reach 30.09 W and 76.99%, respectively. The average charging and discharging power densities of the PBTES unit at a flow rate of 0.5 L/min are 81.94 kW/m3 3 and 47.79 kW/m3, 3 , respectively, which are 39.8% and 242.8% higher than those of the STTES unit. This work demonstrates high-power-density PBTES technology for normal-temperature applications.