Numerical simulation study on optimizing charging process of the direct contact mobilized thermal energy storage

Mobilized thermal energy storage (M-TES) system is considered as an attractive alternative to supply heat to distributed heat users, especially when the waste heat from industries is used as a heat source. From our previous study it was known that the charging time of M-TES system was more than four times of the discharging time, which was a critical issue for the application of M-TES. To improve the charging performance of the system and further understand the mechanism of melting process, a 2-dimensional (2D) numerical simulation model was developed in ANSYS FLUENT. The model was validated by the experimental measurements. The results showed that the model could be used for the engineering analysis. With the validated model, different options to shorten the charging time were investigated including increasing flow rate of thermal oil, creating channels before charging and adding wall heating. Correspondingly, around 25%, 26% and 29% of the charging time could be reduced respectively compared to the experiment with a thermal oil flow rate of 9.8 L/min, according to the numerical simulation. In addition, if the last two options could be applied simultaneously, more than half of the melting time might be shortened without changing the flow rate of thermal oil.