Flow boiling in confined spaces under spatially and temporally varying heat flux conditions

Increasing the power density and efficiency of electric motors is crucial for electrification in automotive or aerospace applications. This has initialized a shift from traditional physically separated motor and drive systems to more compact and power dense integrated motor drives, where power electronics and motor share a common enclosure. A major issue for this integration is cooling, as conventional cooling techniques are insufficient to reach high power densities with associated high heat losses per volume. In this project proposal, flow boiling is investigated as a new cooling technique, as it achieves higher cooling rates at lower temperature differences than conventional techniques. However, hot spots in the machine are a significant risk as they may create locally a too high concentration of vapor, leading to a very low local heat evacuation. Understanding the formation of hot spots in electric machines and power electronics is very challenging, because of the complex heat dissipation rates that vary both spatially and temporally. This is a new and fundamental research area, which will be studied in a separate experimental setup with well defined geometry, making it easier to investigate. The results of the experimental study will be used to derive correlations and models, which will enable the design of integrated motor drive with flow boiling cooling. The proposal is a collaboration between a heat transfer research group and an electric drive research group.