An Innovative Hybrid Nanofluid Spray Cooling Based Thermal Management System for Efficient Cooling of Electric Vehicle High Power Electronics

In recent years, as electric vehicles gained popularity and countries introduced policies for clean energy and clean environment, thermal management of electric vehicle (EV) high power electronics became a research focus due to high power density, chip miniaturization, dense packaging and increased vehicle speeds and mileages. Heat dissipation in high power electronics of current electric vehicles (EVs) can reach up to 500 W/cm2, and it may exceed 1000 W/cm2 in future EVs. Such a high heat flux may not be removed by even efficient cooling technologies (for instance, spray cooling) due to the limited heat removal capacity of existing thermal fluids, such as water and dielectric fluids. To address this issue, the spray cooling potential of the next generation thermal fluid, called the hybrid nanofluid, is proposed in this research.
Research suggests that the hybrid nanofluid (dispersion of two different nanoparticle types in the base fluid) possesses synergistic thermal properties, where its thermal conductivity is higher than that of the base fluid and single-particle nanofluids. In this proposed research, the hybrid nanofluid will be used in spray cooling applications that may address heat dissipation challenges in high power electronics of current and future electric vehicles. Each spray droplet will comprise hybrid nanoparticles that can extract a large amount of heat due to its synergistic thermal behavior. The preliminary results of this research show that the hybrid nanofluid spray cooling can remove the heat dissipation flux of EV high power electronics modules while keeping them within safe temperature levels. On the other hand, spray cooling using traditional fluids (such as water and dielectric fluids) cannot remove the heat dissipation flux of EV high power electronics resulting in temperatures higher than the device failure temperature. This is because existing thermal fluids exhibit low heat transfer coefficients due to their poor thermophysical properties. This project will investigate both one-sided and two-sided cooling approaches for the hybrid nanofluid spray cooling of EV high power electronics. Furthermore, the package thermal resistance of EV high power electronics will be reduced using a thickness optimization approach for different layers of EV power electronics module. The preliminary results of this proposed research indicate that a ceramic material used in a power electronics module contributes a great deal of total package thermal resistance. In this proposed research, the thickness of the ceramic material will be optimized such that it can withstand high voltages while adding a minimum thermal resistance to power electronics packaging. Also, the temperature effects will be considered in the thickness optimization study, as power electronics modules operate at high temperatures that may affect the dielectric strength of a ceramic material used in it. Moreover, new materials with even better dielectric and thermal properties than currently used ceramic materials (such as alumina and aluminium nitride) will also be investigated in this proposed research. Furthermore, the cleaning and re-suspension mechanisms for hybrid nanofluid spray residue will be investigated in this project. This research will reveal the spray cooling potential of the hybrid nanofluid for effective thermal management of high power electronics of both current and future electric vehicles. Although hybrid nanofluids proposed in this research may pose potential threat to aquatic and terrestrial environments, it will be used in the closed loop confined space once integrated into EVs and will not be exposed to the environment.