Role of orientation of fins in performance enhancement of a latent thermal energy storage unit

In this paper, the role of orientation of fins in performance enhancement of a horizontal Latent Thermal Energy Storage Unit (LTESU) is investigated. Stearic acid is used as a phase change material (PCM) that is placed in the annulus of isothermal copper tube and adiabatic steel shell. Two-dimensional, transient, buoyancy driven numerical computations based on enthalpy porosity method are performed after validating against experimental results. Five different angular positions of the fins are investigated by varying 0 degrees <= theta <= 90 degrees. The fin angle theta = 90 degrees produces lambda-fin arrangement while theta = 30 degrees yields Y-fin arrangement. The melting rate significantly increases in case of Y-fins and substantially reduces in case of lambda-fins. The overall melting time of the system is reduced while energy accumulation is increased by Y-fins arrangement. Moreover, the thermophysical effects of fins and shell are studied in detail. The high fin length to thickness ratio and high thermal diffusivity of the shell significantly enhances the melting performance of LTESU. The increase in HTF temperature also increases the heat transfer rate and reduces melting time. Lastly, two important correlations are proposed which can accurately predict the melting and heat transfer performance of LTESU for a large range of HTF temperatures.