LAUSR

In cascaded latent heat storage (CLHS) systems, the phase change processes of phase change materials (PCMs) can hardly sync due to different parameters in each stage. Hence, the thermodynamic analyses based on the static state hypothesis have limitations. In this study, a dynamic heat transfer model, which can describe the transient variation of the PCM temperature, was developed. Based on the model, six objective functions were defined to evaluate the CLHS system performance. The differential evolution (DE) algorithm was used to optimize the melting temperatures and mass of PCMs under different conditions. The results indicate that the objective functions based on the discharging process are superior to those based on the charging process, and they can be selected as optimization criteria according to specific design purposes. The switching operation can effectively improve the CLHS system performance for the unsteady heat sources that include a drop in temperature. The more extensive the temperature fluctuation range, the more significant the improvement. Furthermore, the stage number and the maximum discharging time have an important impact on the system efficiencies, and the former should be longer than the maximum charging time. This study provides theoretical guidance for practical applications of CLHS systems.