Numerical study on the effect of fin geometry on the solidification characteristics of water-based cold storage cavity

Water-ice latent heat storage is of vital importance for aerospace thermal management. However, the substantial volume expansion accompanying the water to ice phase transition can induce the ice spike formation during solidification in the cold storage cavity, threatening the integrity of the package shell and causing leakage of phase change material. To improve the solidification characteristics of a cold storage cavity with reserved space, a numerical simulation method was employed to investigate the effects of the fin height ratio (the ratio between the near-wall fin height and the central fin height), the distance between fin tip and the liquid level, and the fin thickness on the phase interface morphology and solidification time of a water-based cold storage cavity during the solidification process. Furthermore, the safety cold storage efficiency index is proposed to evaluate the actual effect of the cold storage cavity. The results show that when the total area of fins is fixed, compared with the bare square cavity, the fin structure with a height ratio of 1 achieves a superior ice spike suppression effect, reducing the ice spike height by 5.73%. By contrast, a fin height ratio below 1 is more conducive to improving the cold storage performance, yielding a 66.09% reduction in the solidification time. Under the condition of fixed initial liquid level in the square cavity, further adjusting the height of the fin structure with a height ratio below 1, it is found that increasing the fin height can reduce the solidification time by 69.16%, while reducing the fin height can reduce the ice spike height by 5.53%. Additionally, by adjusting the thickness of the fin structure with a height ratio below 1, it is found that the fin thickness of 0.2 mm limits improvement in solidification performance. In summary, the proposed SCSEI establishes a synergistic balance between structural safety and heat transfer efficiency, thereby providing clear geometric design criteria for water-based cold storage units. These findings offer a practical and broadly applicable strategy for developing high-performance, reliable thermal management systems across aerospace and industrial energy storage applications.