Discharge improvement of a phase change material-air-based thermal energy storage unit for space heating applications using metal foams in the air sides

This study examines the energy discharge of a phasechanging material (PCM)-based air heat exchanger using a metal foam inside the heat transfer fluid (HTF) channel. Such systems have various potential applications in the heating space and building ecosystem. Thermal energy storage (TES) often utilizes air as the HTF, which limits the heat transfer performance due to the low thermal conductivity. This paper aims to address this drawback via incorporating a metal foam into the HTF channel to enhance the thermal performance between the heat transfer fluid (air) and the PCM, which is considered as the novel side of this study. The combined system is mathematically modeled with an symmetrical, three-dimensional computational fluid dynamics method for various flow rates and inlet temperatures of the HTF with different geometric parameters of the metal foam. This study indicates the advantage of utilizing the porous medium in the air channel. The results show the HTF flow rate has a great influence on the discharging rate. The presence of the porous medium in the system improves the discharging process by 116% compared with a nonporous medium system at the same flow rate. The discharging time decreases by increasing the porosity, and the value of 90% is found as the best porosity value at the flow rate of 0.005 kg/s in this system. The solidification rate is proportional to the pore density because of the surface area impacts of the porous medium, also the pressure-drop and the pumping required are highly affected by the mentioned dependent parameters.