THERMODYNAMIC OPTIMIZATION OF THE THERMAL-PROCESS IN ENERGY-STORAGE USING MULTIPLE PHASE-CHANGE MATERIALS

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