Magnetically- regulated close contact melting for high-power-density latent heat energy storage

Abstract

Rapid melting of solid-liquid phase change materials (PCMs) is critical to the high-power-density latent heat energy storage and efficient thermal management. The pressure-enhanced close contact melting is seen as a promising method because of the suppressed heat transfer resistance between the heating surface and the melt front during thermal charging, but it remains a key challenge how to tactfully apply external pressure for a practical device. Herein, we present a magnetically-regulated close contact melting strategy for rapid melting of PCMs from the perspective of the practical application. In this method, a PCM and a permanent magnet are contained inside a highly thermally conductive vessel, and the magnet regulated by another one can push the solid PCM toward the heating surface. Consequently, the superheated molten PCM can be instantly removed from the heating surface due to the magnetic force so as to achieve the suppressed thermal resistance. The temperature-control performance of paraffin wax is evaluated under various applied external forces and heat loads. Experimental results indicate that the heating surface temperature can be controlled near the melting temperature of PCM even under a relatively high heating flux. With applying the external pressure of 900 Pa, the average heat transfer resistance is reduced to lower than 4.5 × 10−4 K·m2·W−1. Finally, a closed thermal management device is fabricated and measured by using a graphite vessel to encapsulate the magnet and the PCMs such as paraffin and low-melting-point alloy. This device demonstrates good recyclability for repeated thermal charging/discharging. Our work provides a new method to develop the practical thermal management device based on pressure-enhanced close contact melting.