Analysis of heat transfer in latent heat thermal energy storage using a flexible PCM container

Latent heat thermal energy storage (LHTES) affords superior thermal energy capacity and compactness but has limited applications due to the low thermal conductivity of phase change materials (PCMs). Several researches have focused on the improvement of heat transfer and reducing the total melting time of PCMs in LHTES system. Few researches, however, have used flexible PCM containers for this purpose. This study used a flexible elliptical container as a PCM container for improving LHTES heat transfer performance. The effects of the axis ratio (AR) and temperature difference on the thermal charging performance were numerically studied within a single container. Smaller AR values improved the heat transfer performance by promoting heat conduction and natural convection inside the containers. The enhancement rate was increased by 1.1–2.7 times for an AR range of 0.05–0.20 compared to a classic circular container (AR = 1). In addition, the elliptical container showed superior in terms of energy density reduction. Therefore, the elliptical container with optimum AR range (0.05–0.20) can be considered a suitable configuration for effective heat transfer enhancement of PCM containers.