Discharging performance evaluation and optimization of a latent heat thermal energy storage unit with helm-shaped fin

Latent heat thermal energy storage with phase change materials can help mitigate the imbalance between the energy supply and demand. Improving the discharging efficiency is crucial to the performance of thermal energy storage units. This paper explores the enhancement performance of helm-shaped fin on phase change materials solidification in a vertical shell-tube storage unit. Numerical model was built to examine the solidification performance of the thermal energy storage unit and its effectiveness was validated by experimental data from literature. The effect of the dimensionless offset (O, O , defined as the ratio of the minimum distance between the rectangular part of helm-shaped fin and the tube to the distance between the shell and the tube) on the thermal performance was firstly investigated. Results showed that an O of 0.458 is optimum, which shortens the solidification time by 23.9% compared to the O of 0. With this offset, the effects of volume, thickness and height ratios of the annular part to the rectangular part of the helm-shaped fin were further investigated. Results showed that the phase change materials solidification rate increases as the thickness ratio increases and height ratio decreases. The optimum thickness and height ratios are 8 and 0.473 respectively, which reduces the solidification and melting times by 54.5% and 22.1% respectively compared to the traditional annular fin at the same fin volume.