Numerical analysis of heat transfer characteristics in a flywheel energy storage system using jet cooling

A flywheel energy storage system (FESS), with its high efficiency, long life, and transient response characteristics, has a variety of applications, including for uninterrupted power supplies and renewable energy grids. The heat produced by the system as a result of power loss has a significant negative impact on the long-term stability in a vacuum environment. This paper proposes an impingement jet cooling structure with rotating axis to facilitate the heat dissipation of FESS. The implications of the cooling medium, nozzle length, cavity zone diameter, and nozzle diameter of the impingement jet cooling structure on flow and heat transfer performance are studied by field synergy theory. Additionally, the structural parameters are optimized using the response surface method. The Nusselt number, friction coefficient, field synergy angle, comprehensive coefficient of heat transfer, and temperature field are analyzed. Heat transfer can be improved by decreasing the diameter of the cavity zone, lengthening the nozzle, and increasing the nozzle diameter. The pressure drop of the optimized structure is at least 62.48% less than that of the unmodified structure, while the temperature increase of the cooling medium is nearly 3.5 times higher.