Experimental and numerical investigation of the latent heat thermal storage unit with PCM packing at the inner side of a tube

Latent heat thermal storage systems (LHTS) are widely studied for solving the mismatch between the energy supply and demand in time and space. Most of the previous studies are focusing on the systems with the phase change material (PCM) packing outside the tube. The characteristics of a LHTS with the PCM packing at the inner side of a tube has been rarely reported. In this paper, a visible experiment with a horizontal circular tube filled with PCM has been presented. The phase interface as well as the temperature of the PCM could be monitored varying with time. The performance of the LHTS system with the PCM packed at the inner side or outer side of the tube are compared at different filling rates (40-90%). The results show that the tube with PCM packing inside has a better comprehensive performance when the filling rate is more than 62%, as compared to the tube with the PCM packing outside. Furthermore, an enthalpy-porosity method verified by the experimental data is adopted to simulate the charging and discharging processes of the LHTS systems with other different tube shapes. The horizontal and vertical ellipse units and triplex tube units with three different shapes of inner tube are simulated to enhance the performance of basic circular unit. The performance evaluation indicators including charging and discharging time and power per mass of PCM in charging (POC), discharging (POD) and circulation (POA) are chosen to compare the performance. The triplex tube with an inner horizontal ellipse shaped tube (TTHE) reveals the best performance with a 118.3% increased POA. (C) 2020 Elsevier Ltd. All rights reserved.