Numerical investigation of coil cross-section geometry on ice thermal energy storage performance

• 2D enthalpy–porosity model simulates ice solidification. • Coil shape alters freezing time up to 11.2% (equal area). • Equilateral triangle solidifies in 9100 s, best baseline case • Higher triangular aspect ratio (AR) enhances freezing performance. • AR = 2 reduces solidification time by 17.1% vs circular. Ice thermal energy storage (ITES) systems are widely employed to shift cooling demand from peak to off-peak hours, thereby improving energy efficiency and reducing operational costs. Enhancing the charging performance, defined here as the rate and effectiveness of thermal energy storage during the freezing process, remains a key challenge due to the inherently low thermal conductivity of ice. In this study, a comprehensive numerical investigation is performed to examine the influence of heat-transfer coil cross-sectional geometry on the solidification behavior of water in a square ice-storage enclosure. Circular, equilateral triangular, square, hexagonal, and both vertically and horizontally oriented elliptical coil geometries are analyzed under identical thermal and geometric conditions using the enthalpy–porosity method. The results demonstrate that coil geometry has a pronounced impact on ice-making time. Among the investigated configurations, the equilateral triangular cross-section exhibits the best performance among the investigated geometries, achieving complete solidification in 9100 s, which is 11.22% faster than the conventional circular coil. Furthermore, the effect of the height-to-base aspect ratio (AR) of triangular coils systematically investigated for AR values of 0.5, 1, 1.5, 2 and with the equilateral triangle corresponding to AR ≈ 0.67. Increasing AR significantly accelerates the freezing process, with AR= 2 yielding the shortest total solidification time of 8500 s representing a 17.07% reduction relative to the circular geometry. These findings highlight the potential of coil cross-sectional geometrical shaping as a simple and passive design strategy to enhance the charging efficiency of ITES systems without increasing PCM volume or system complexity.