Examination and optimization of the design parameters for the thermal hysteresis phenomenon of the phase change material

Abstract

The current paper examines the influence of the thermal hysteresis phenomenon on the results of the simulation and optimization of the design parameters for a modelled Phase Change Material (PCM) sphere and for a large scale Thermal Energy Storage (TES) system integrated with PCMs. It first investigates the accuracy of the simulation results with and without taking into account the thermal hysteresis by relying on the effective heat capacities of the heating and cooling enthalpy-temperature curves compared to the equivalent heat capacity in accordance with the melting time, energy output and usage temperature. In addition, the paper assesses the influence of the design parameters and capsule envelope material variation when the the thermal hysteresis phenomenon is exhibited by the spherical PCM capsule. Second, the study examines the impact of the thermal hysteresis phenomenon on the accuracy of the design parameters optimization for the large scale TES system by applying the adaptive simulated annealing algorithm to seek for the optimal parameters. The study highlights that the thermal hysteresis contributes to a variation in the simulation outputs for the modelled sphere by increasing the amount of recovered energy from 3.03 to 4.5 kJ and reduces the melting time from 8 to 5 min. The difference in the simulation results is not observed during the optimization of the energy content, hence, considering, or not the hysteresis phenomenon during the optimization process, contributes to similar optimum design parameters.