Exergy Analysis and Optimal Removal Time for a Lithium-Fluoride Phase Change Material

In this study we consider the transient analysis of a thermal energy storage system modeled as a rectangular thermal system. The working fluid is assumed to be incompressible, which passes through a pipe. The energy transfer from the higher temperature surrounding domain to the working fluid is due to conduction through the phase change material and by convection to the working fluid. We apply an integral technique to determine the behavior of the different temperature profiles as a function of time. In addition we consider second law aspects of the system and isolate those irreversibilities which reduce the availability. Lastly, we propose a normalized figure of merit characterizing the optimal ratio of exergy extraction to exergy change of the storage system as a function of removal time.