Comparison of Thermal Performance between Annular Fins and Longitudinal Fins in Latent Heat Storage Unit

As a simple and effective method of heat transfer enhancement,fins are widely used in latent heat storage systems.However,the choice of annular fins and longitudinal fins has always been controversial.In this paper,the melting process of phase change material(PCM) in annular fins and longitudinal fins latent heat storage units with the same volume is numerically simulated.To ensure the same thermal penetration,three-dimensional spaces occupied with fins are specially controlled to be the same.Combined with finned structures,the effects of natural convection(NC),placement mode and heat transfer fluid(HTF) inlet direction on the melting process are studied.The results show that the melting time in annular finned structure is always 10%less than that in longitudinal finned structure,which demonstrates the superior of the annular fins in the latent heat storage unit.The melting time is the shortest in vertical unit with annular fins and HTF inlet at the bottom.Additionally,the correlation formulas of the liquid fraction are proposed in the vertical unit with HTF inlet at the bottom.