Study on melting process of latent heat energy storage system by nano-enhanced phase change material under rotation condition

The utilization of phase change material in latent heat thermal energy storage technology is hindered by its limited thermal conductivity. This research aims to enhance the melting properties of a triplex-tube latent heat thermal energy storage unit through active strengthening (rotation mechanism) and passive strengthening (nanoparticle, longitudinal fin) heat transfer methods. A numerical investigation is conducted to examine the influence of nanoparticle percentage and rotation speed on various melting properties, including melting time, liquid fraction, heat absorption rate, and temperature response. The results demonstrate that the inclusion of 2.5 % and 5 % Al2O3 nanoparticles can significantly reduce the melting time by 58.49 % and 57.59 % respectively, while also increasing the average heat absorption rate by 126.53 % and 123.37 % at a rotation speed of 0.1 rpm. The findings from the Taguchi method suggest that rotation speed has a greater impact on melting duration and heat absorption rate compared to nanoparticle concentration. Moreover, maintaining a constant rotation speed, and a higher nanoparticle proportion can lead to an increase in dynamic viscosity and the settling of nanoparticles, which adversely affects the melting process efficiency.