THE EFFECT OF FREEZING AND MELTING ON THE EFFICIENCY OF LATENT-HEAT STORAGE-SYSTEMS

This paper presents a thermodynamic analysis of latent heat storage sy stems (LHSSs). The study is based on a model that, although simplified , takes full account of the physics of the phase-change process that t akes place in the LHSS during charge and discharge. The model characte rizes an LHSS with only two parameters and four operating temperatures , This simplicity allows a detailed study of the unit. Two different s ituations are analyzed, The first is an LHSS in which the phase-change material (PCM) is stored in a single container. The second is an LHSS with many small cells containing the phase-change material. The simpl ified model presented in this paper is successful in describing the ef fects of the physics of the phase-change process on the performance of LHSSs. Optimum efficiencies and phase change temperatures in the LHSS s related to the inlet temperature of the charge fluid are obtained ba sed on exergy analysis. The results also indicate that the insulating effect of the solid layer during the discharge process reduces both th e exergetic efficiency and the storage capacity of the unit. On the ot her hand, the study points to enhanced heat transfer inside the unit a s very important for improving LHSSs performance.