Melting performance assessments on a triplex-tube thermal energy storage system: Optimization based on response surface method with natural convection

The low thermal conductivity of phase change materials significantly affects the heat storage and release performance for a phase change energy storage system. To alleviate this issue, a novel triplex-tube latent heat thermal energy storage system is designed and the melting behavior of phase change materials is studied numerically. On the premise of a fixed total volume of phase change material, the multi-parameter optimization design of the system is carried out by the response surface method. The fluid-structure coupling function of each parameter is fitted. Compared with the original model for the triplex tube, the melting performance of the optimized model is improved by 23.87%. The internal temperature fluctuation is found by dynamic temperature response, and the mechanism is explained by dynamic flow rate study. The improvement of melting performance by natural convection after optimization is also studied. The influences of the physical parameters (fin length, initial temperature of phase change material, inner and outer tube wall temperature, and fin material) of the optimization model on the melting performance of the system are quantified, as well. The effect of fin length (30-35-40 mm) on melting performance is found to be less than 11.47% and the effect of thermal conductivity of fin on the melting process is not obvious.