Effect of Metallic Shell on Energy Storage Characteristics of Macro-Encapsulated PCM System

Macro-encapsulated phase change material (PCM) is widely used in energy storage applications for its high energy storing ability without high temperature rise. The effect of shell thickness on energy storage performance of multiple encapsulated PCM systems subjected to flow of hot heat transfer fluid (HTF) is numerically studied by developing a 3D model. The model considers different phases present in the domain such as solid PCM, liquid PCM, metallic shell and HTF. The geometry of the capsules is resolved and the fluid flow between the capsules and also natural convection within the capsules are also captured. Coupled fluid flow and enthalpy model are used to solve the flow of HTF and phase change process of PCM. Melting and energy storage of three different multi-capsule systems with paraffin encapsulated in aluminum shells subjected to heat transfer by flow of high temperature water are studied. The 3 cases have large shell thickness (1 mm), intermediate shell thickness (0.5 mm) and negligible shell thickness (0 mm). The results show that total energy stored in the 0 mm shell system is 5.87 and 14.66% higher than that of 0.5 and 1 mm shell system, respectively. But the melting in 0 mm shell system takes 60.22 and 87.09% more time than that of 0.5 and 1 mm shell system.