Novel high heat flux thermal management with combined supercritical CO2 and a microjet heat sink

The limited operational range of electric vehicles (EVs) continues to be a significant hurdle to their advancement. The Insulated Gate Bipolar Transistor (IGBT) embedded in the inverters of these vehicles generates significant amounts of heat while operating and greatly impacts the vehicle’s overall performance. To improve the efficiency of EVs, the present study puts forward a new thermal management system comprising a multi-layer microjet heat sink with supercritical carbon dioxide (sCO2) as the working fluid for cooling IGBTs with high heat fluxes. The IGBTs and diode pairs are modeled based on the motor inverter of the Toyota Prius. Each IGBT with its diode pair is embedded on a direct bound copper beneath the baseplate of the heat sink, generating heat fluxes between 120–360 W/cm2. Inlet temperatures ranging from 25 to 35 °C and mass fluxes ranging from 500–2000 kg/m2 s were used in this study. The numerical simulations are performed using the finite volume method, and the numerical procedure is validated against the experimental and numerical data. Results show that the maximum global heat transfer coefficient of sCO2 is 60.4 kW/m2 °C and that the higher inlet temperature can positively or negatively affect the thermohydraulic behavior of sCO2 depending on operating conditions. Increasing the inlet temperature at q“ < 360 W/cm2 enhances the heat transfer coefficient over different layers up to 33 %, while at q” ≥ 360 W/cm2, the convective heat transfer coefficient is reduced using a higher inlet temperature. Despite a higher convective heat transfer coefficient and lower IGBT temperature with water at higher heat fluxes, sCO2 exhibits 5 times better temperature uniformity, showing promising potential as an advanced coolant for future cutting-edge cooling systems.