Effect of Capsule Shape on Melting and Energy Storage Rates for Encapsulated PCM-Based Systems

Latent heat thermal energy storage using phase change materials (PCM) has become a topic of interest as it has the advantages of high energy storage density. Encapsulated PCM energy storage systems are being widely studied as they have large heat transfer area available for charging by the heat transfer fluid (HTF). The shape of the capsules can considerably affect the melting rate and thus the energy charging characteristics. In this work, a numerical analysis of encapsulated PCM system with a single capsule but with different shapes has been carried out by developing a 3D finite volume-based model. The developed model is used to predict the melting and energy storage rates of spherical, cuboidal, cylindrical and triangular prism-shaped capsules keeping the PCM volume constant. It is observed that the time required for melting is reduced by 3, 10.39, 22.64, 11.68% for cubical, horizontal cylinder, horizontal prism and vertical prism capsules as compared to the spherical capsule having the same volume. Thus, the horizontal prism capsule has the best melting and energy storage rates among all the considered shapes.