numerical investigation of melting-freezing cycle of phase change material pcm contained in finned cylindrical heat storage systems integrated with nano-particles additives

Thermal energy storage systems containing phase change materials are widely used in industry. this investigation was done to improve the heat transfer performance of the charging and discharging processes (melting/freezing cycles) for heat exchangers containing phase change materials (paraffin wax) with nano-particles ( ), based on the total required time to complete the charging and discharging processes during the cycle. using the enthalpy porosity technique to analyze the phase change phenomenon during the charging and discharging processes, a numerical model has been developed to study the heat transfer performance of the cycle in contrast, the influencing parameters, such as the geometric, thermophysical, and hydraulic parameters, are changed. the study was carried out in four arrangements: a base case, a reversed chamber, and each with two flow directions. for each arrangement, the effects of the volume fraction of the nano-particles (0, 2, and 5%) on the melting/freezing average have been studied. the results show that by changing the above parameters, the total charge and discharge cycle time of the heat exchanger improves from 101 hours to 56 hours, which means 44.5% for the inversed chamber and the direction of flow, and 5% for nano-particles.