Numerical study of jet impingement cooling methods for improving heat transfer in a flywheel energy storage system

Flywheel energy storage systems (FESS) have garnered a lot of attention because of their large energy storage and transient response capability. Due to the limited space and vacuum, heat produced by FESS is typically not adequately dispersed, which can lead to demagnetization and severe thermal stress and compromise the ability of equipment to operate safely. Since the engine is the primary generator/motor of heat, the heat dissipation problem cannot be ignored. To evaluate the cooling efficiency of FESS, three types of water-cooling structures are constructed: axial jet, the opposite-hole-arrangement jet and the staggered-hole-arrangement jet nozzles. Using the Ω vortex identification method, a large number of vortices can be observed in the reflow channel of both the opposite-hole-arrangement jet and the staggered-hole-arrangement jet structure. The turbulent kinetic energy of staggered-hole-arrangement jet nozzle is higher than that of the opposite-hole-arrangement jet nozzle. It is found that raising the inlet velocity of coolant in the staggered-hole-arrangement jet structure can decrease the temperature of motor components. The staggered-hole-arrangement jet cooling nozzle with coolant applied to provide passive liquid cooling for FESS is the best cooling method described in the study. The heat dissipation effect is greatly influenced by the environmental conditions, and in order to ensure the safe operation of FESS during the winter, it is required to consider adding 50 % antifreeze.