Thermodynamic optimization of the thermal process in energy storage using multiple phase change materials

This article presents a thermodynamic analysis of the energy charge/discharge processes in a latent heat thermal storage system using multiple phase change materials (PCMs). This analysis is based on a lumped model for the PCMs which assumes that a PCM is a thermal reservoir with a constant temperature of its melting point and a distributed model for the heat transfer fluid which assumes that the temperature of the fluid Varies in its flow path. Analysis is carried out for thermal storage systems using two, three, as well as five PCMs. Analytical results show that the exergy efficiency can be enhanced dramatically using multiple PCMs compared with a single PCM. Illustrative results are presented and discussed in terms of their potential applications in efficient thermal storage devices. (C) 1997 Elsevier Science Ltd.