Numerical investigation on melting and energy storage density enhancement of phase change material in a horizontal cylindrical container

摘要

Thermal energy storage (TES) plays a significant role in storing heat energy during the availability of a source. The phase change material (PCM) storage density is high, but its meager thermal conductivity leads to ineffective heat transfer. This mathematical modeling work simulates two different heat transfer tube (HTT) arrangements in a horizontal cylindrical container to melt the PCM using the enthalpy-porosity method. Case-1 with a single HTT at the centroidal axis and Case-2 with multiple tubes spread radially. Cases-1 and 2 are observed with melting and solidification duration of 39.8 and 184 minutes, and 69.83 and 292.5 minutes respectively. Case-1 has a shorter melting and solidification time because of the optimal HTT location. Case-2 is observed with a high heat storage density of 224.95 MJ/m(3), compared to Case-1 with 224.571 MJ/m(3). Nusselt number is higher for Case-2 (385.86) during charging and higher for Case-1 (208) during discharging. Nusselt number initially varies for both cases due to effective heat convection at the start; however, Case-1 has a shorter melting duration with its energy density lower than the Case-2. Based on the obtained results, it could be suggested that Case-1 could be applicable when simultaneous heat transfer requires less energy storage and a faster melting rate, while Case-2 could be used in places that demand a higher storage density.