Investigation of the charging and discharging cycle in a thermal energy storage system

Phase change materials (PCMs) are the most suitable for storing thermal energy, as they store latent heat with a high storage energy density per unit volume. PCMs are a proven scheme of thermal management in the context of cooling electronic devices. This paper focuses on enhancing the efficiency as well as reducing the time during charging and discharging of the PCMs. Various aluminum fin structures in contact with PCM are analyzed using the finite volume method. Lauric acid-PCM is employed for the analysis in applications at low and mid-temperature ranges. The analysis was carried out with a 40 mm x 40 mm 2D vessel, a heat flux of 180 W/m2 from the top surface, and a 3 mm-thick aluminum plate; the other sides are insulated with glass wool. Three cases are considered to contrast efficiency: vessels with no fins, vessels with 3 mm-diameter straight aluminum fins, and vessels with 1 mm-diameter periodic-structured aluminum fins (mesh fins) with a 10 mm cell base size. The three cases are analyzed in Ansys Fluent for charging time; the straight and periodic structured fins are also analyzed for discharging time. It was inferred from the results that vessels with straight fins had a 58% decrease in charging time as compared to vessels with no fins. Vessels with periodic structured fins had a 82% decrease in charging time as compared to vessels with no fins. Also, the periodic structured tubes required 61.5% less time to discharge than the straight tube structure. Hence, Periodic Structured fins and tubes could overcome the problem of a long time taken for charging and discharging PCM.