Influence of fluctuating heat sources on multiphase thermal storage process: Thermal performance optimization utilizing the Taguchi method

Abstract

The application of thermal energy storage technology in scenarios requiring rapid heat storage and release is of critical importance. This study introduces a novel composite thermal energy storage configuration, comprising a solid-phase change material (PCM) in the lower half and water in the upper section. By utilizing density variations induced by PCM phase change, the design facilitates natural convection between the two media, thereby enhancing heat transfer efficiency. The investigation focuses on the impact of unsteady pulsating heat fluxes on heat and mass transfer dynamics during the charging process. A comparative analysis of experimental and numerical results delineates the evolution of the solid–liquid interface within the PCM and the total melting time, validating the proposed thermal model. The findings demonstrate that the amplitude of the pulsating heat flux significantly influences the mean energy storage rate (ESR), while having a negligible effect on the total thermal energy absorbed by both water and PCM. Compared to a reference configuration with a heat source amplitude of 2.5 K, a half-period of 25 s, and a base temperature of 334.15 K, the Taguchi-optimized thermal storage structure exhibits a 28 % and 30 % improvement in the average ESR for the PCM and water, respectively, along with a 20 % reduction in the total melting time.