Effect of periodic heat source conditions on melting performance of composite phase change energy storage tank: A numerical optimization

To improve the low thermal conductivity challenge of phase change materials (PCM) in energy storage applications, this study introduces a composite thermal energy storage (TES) unit integrating PCM with water. Numerical simulations are employed to examine the influence of a fluctuating heat source on the heat charging dynamics of the unit. Results derived from Taguchi analysis indicate that increasing the amplitude, half-period, and initial temperature of the fluctuating heat source consistently reduces the melting time. The initial temperature exhibited the most significant effect on accelerating the charging process. Furthermore, elevating the amplitude and initial temperature led to a corresponding increase in the mean energy storage rate of the PCM while extending the half-period initially enhanced, then diminished, the mean energy storage rate. The optimal heat source parameters are identified as Case 4, characterized by an amplitude of 6.5 K, a half-period of 15 s, and an initial temperature of 352 K. Compared to the baseline heat source conditions, this configuration demonstrated a 33.7 % improvement in the mean energy storage rate within the PCM, a 48.9 % increase in water, and a 21.2 % reduction in charging time. These findings indicate that the heat source fluctuation has a significant influence on the energy storage process of the complex energy storage unit.