Heat exchanger design can improve the performance of PCMs
According to a recent review article, optimising the design of heat exchangers in latent heat thermal energy storage systems (LHTES) is one way of improving the thermal conductivity of phase change materials (PCMs).
The main advantage of phase change materials (PCMs) is their high heat capacity per unit volume and their almost constant phase change temperature. However, low thermal conductivity is one of the main drawbacks of PCMs, resulting in slow heat transfer. This may restrict the potential applications of PCMs in thermal energy storage. According to a recent review article, the time-consuming phase change of PCMs could be shortened by using various methods such as: increasing the temperature difference between the PCM’s melting point and the inlet temperature of the heat transfer fluid, increasing the flow rate of the heat transfer fluid, using multiple PCMs, and using appropriately constructed heat exchangers.
Heat exchangers are an integral part of PCM-based thermal energy storage systems, i.e. latent heat thermal energy storage (LHTES) systems. The authors of the literature review present the different types of heat exchangers used in LHTES and their parameters that influence the phase change time.
The various types of heat exchangers used in LHTES systems include: plate heat exchangers, helical-coil heat exchangers, double-tube heat exchangers, triple-tube heat exchangers, multi-tube heat exchangers, heat exchangers with encapsulated PCMs, enclosure-type heat exchangers.
The following table presents the impact of these different types of heat exchangers (HX) on the performance of PCMs. Modifications in the construction of heat exchangers reduce the melting time of the phase change materials but increase the solidification time.
Radomska, E.; Mika, L.; Sztekler, K.; Lis, L. The Impact of Heat Exchangers’ Constructions on the Melting and Solidification Time of Phase Change Materials. Energies 2020, 13, 4840. https://doi.org/10.3390/en13184840