Optimization and numerical investigation on phase change energy storage structures with eccentric rotation using gradient metal foams

The study integrates active and passive enhanced heat exchange technologies by utilizing gradient metal foams and specific rotation conditions in the phase change energy storage process. The research evaluates the impact of various unit eccentricities, foam structures, and rotation speeds on the melting process, employing numerical models based on the non-thermal equilibrium model and the enthalpy hole method. Results indicate that a positive pore gradient structure, as opposed to uniform or negative gradients, enhances heat source diffusion, leading to improved overall heat exchange uniformity and temperature response. For cases with the same gradient structure, the melting time for Case 6 and Case 9 decreases by 20.07 % and 23.99 %, respectively, compared to Case 3 when the rotation center distance is increased. Moreover, the total heat storage increases by 0.45 % and 0.46 %, respectively. Furthermore, the research utilizes the Taguchi method to optimize parameters such as porosity combination, PPI, rotation center distance, and rotation speed. The study highlights that the pore gradient has the most significant influence on the average heat storage rate and heat storage time, accounting for 49 % and 48.7 %, respectively. Additionally, the interaction among rotation center distance, porosity combination, and rotation speed is notably significant. The optimal configuration for achieving the highest average heat storage rate and lowest heat storage time involves a positive gradient foam structure with a center distance of 200 mm, rotation speed of 0.20 rpm, and PPI of 10.