Enhancing latent heat storage systems: The impact of PCM volumetric ratios on energy storage rates with auxiliary fluid assistance

The present study investigates the effect of different volume ratios of PCM on the melting process and energy storage in the improved thermal energy storage (TES) system using auxiliary fluid. The purpose of using the auxiliary fluid is to benefit from the density difference between the auxiliary fluid and the PCM, which improves the convection heat transfer in the auxiliary fluid and increases the melting speed of the PCM. The auxiliary fluid, which has a higher density, is placed on the solid PCM at the beginning of the melting process and takes the place of the melted PCM during the melting process. This displacement causes better heat transfer between auxiliary fluid, PCM, and hot wall. Five different PCM/auxiliary fluid volume ratios are studied, including 30, 40, 50, 60, and 70% of PCM. The rate of energy storage in the system increases to 0.341 kW/kg, the highest rate of energy stored in the system and in PCM, corresponding to a volume ratio of 30% of PCM. Although the total energy stored in the system increases with an increase in the PCM volume ratio, the energy storage rate in the system increases with a decrease in the PCM volume ratio. Therefore, the optimal use of the most appropriate volume ratio of PCM is of great importance