Effect of iron scrap additives in stearic acid as PCM for thermal energy storage system

The thermal energy storage (TES) system is used to store the heat energy for longer periods and retrieve the heat energy as and when required. Experiments were conducted on the TES system with stearic acid (SA) as phase change materials (PCM) with and without iron scrap additives (IS) filled in spherical capsules. The PCM was filled in high-density polyethylene (HDPE) capsules of spherical shape. The process of charging, discharging, and the heat energy retrieved for the aforementioned PCMs were investigated and compared with various heat sources. The TES tank performance was studied with a variable/constant heat source at different flow rates, i.e. 2, 4, and 6 LPM. The results showed that the TES tank is charged to 70 °C in 204 min with 6 LPM flow rate, whereas for 2 LPM flow rate, the TES tank was charged to 70 °C in 254 min for the variable heat source. In the case of a constant heat source, to reach 70 °C, it took 54 min, 43 min, and 33 min for 2 LPM, 4 LPM, and 6 LPM flow rates, respectively. The total heat capacity of the TES tank at 70 °C was around 10,400 kJ. The output hot water at an average of 45 °C was found to be around 164 litres which means that the heat energy recovered from the TES tank was around 32%. The system with IS along PCM filled in spherical capsules was able to give 25% of hot water in extra than the same capacity of the sensible heat storage system. The results obtained reveal that heating and cooling processes were taking place at a faster rate of 13% with the addition of IS particles to the PCM when compared to pure PCM in the spherical capsules.