Heat Transfer Simulation and Analysis of Thermal Battery

Abstract

This study aimed to establish thermal analysis conditions and techniques for thermal batteries used as special-purpose power sources through comparisons with experimental data. Grid independence was realized, and grids with an error rate of less than 1% were applied. For heat transfer analysis, an unsteady analysis was conducted from 0 to 1,000 s by using commercial software. To apply the experiment results of the housing surface temperature to the analysis, the convective heat transfer coefficient that represents an equivalent temperature tendency was obtained through thermal analysis; its value was 19.2 W/m2·K. Heat transfer analysis was conducted by applying this coefficient to a 2° full model. Through the analysis, the temperature distribution inside the thermal battery and its heat dissipation characteristics were investigated. For an operating time of 870 s, the total averaged electrolyte temperature, top and bottom electrolyte temperature, and middle electrolyte temperature were found to be 457 °C, 441 °C, and 466 °C, respectively. Assuming a minimum operating temperature of 450 °C for the electrolyte, the amount of power generated decreases sharply from the top and bottom electrolyte layers of the housing of the thermal battery. This is because rapid heat release occurs at the top and bottom of the housing compared to the sides. Therefore, improving the insulation performance of the top and bottom of the housing could significantly enhance the operational performance of the thermal battery; reinforcement of the side insulator would also be required. The obtained results could serve as significant basic data for improving the performance of thermal batteries and extending their operating time.