Enhancing the charging performance of the latent heat storage unit by gradient straight fins

Abstract

To improve the charging performance of the latent heat storage units, this paper performs a numerical simulation study of the melting of phase change material under various gradient straight fins employing the enthalpy-porous medium model. Based on the evolution of phase interface and temperature distribution, along with the variation of liquid phase fraction and Nusselt number, we analyze the sole effects of gradient-length and gradient-angle on the melting of the phase change material. Further, we gain the optimized-gradient fins by cooperatively adjusting the geometrical parameters of both the gradient-length and gradient-angle using response surface methodology. The introduction of natural convection of the formed liquid divides the melting process into three stages. Optimizing the geometrical parameters of straight fins could facilitate the fast second stage containing natural convection, leaving no (or less) room for the slow third stage without natural convection. Compared with the uniform fin structure, gradient-length and gradient-angle could reduce the total melting time at most by 48.9% and 8%, respectively. The largest reduction (56.6%) exists in the optimized straight fin structure with the gradient-length of 5.56 mm and the gradient-angle of 5.36°, involving only the first two melting stages without the third stage.