Effect of Internal Flow Channels on Encapsulated PCM with Constant Volume

A numerical study is presented to analyze the effect of internal flow channels on latent heat thermal energy storage (LHTES) systems with encapsulated phase change materials (PCMs) while maintaining constant PCM volume. A 3D cubical domain is modeled with a PCM capsule located at its center subjected to hot heat transfer fluid (HTF). Internal channels are made into the PCM capsules to improve the melting rate. Maintaining a constant volume makes the total latent energy stored constant although the rate of energy storage varies with change of internal radius. The model also captures the natural convection within the capsules. Coupled fluid flow and enthalpy model is used to solve the flow of HTF and phase change process of PCM. Capsules with base radii of 4 mm and 8 mm are studied under four different configurations with the ratio of the channel to the base radius (r/R0) varying as 0.250, 0.333, 0.416, and 0.500. The results show that the melting duration reduces by 42.58% for the capsule with a 4 mm base radius when r/R0 is 0.500. Similarly, the melting duration reduces by 51.15% with an 8 mm base radius when r/R0 is 0.500. For all r/R0 ratios, it is found that the effect of internal channels on energy storage rates and melting time are considerably more for the larger capsule size.