Januar 2026
Although oil spray cooling is a promising cooling concept for electrical engines with high power density, there is a lack of universal measurement data and correlations for design purposes. In this work, an experiment is designed specifically for this application using similarity theory in a generic spray-wall situation. The comprehensive investigation shows a clear dependence of the heat transfer on the oil mass flow density and the droplet energy on impact into the oil film formed on the heated windings. Additionally, the thermal interaction between the spray droplets and the surrounding air is found to be an essential mechanism in oil spray cooling heat transfer. The experimental results are eventually used to derive a Nusselt number correlation, which is valid for a large range of spray Reynolds numbers, oil Prandtl numbers as well as nozzle Weber numbers.
The details can be found in our new article, which was published in the journal "Experimental Thermal and Fluid Science". The full paper is available here:
https://doi.org/10.1016/j.expthermflusci.2025.111656
We thank Dr. Nicolas Brossardt and Dr. Sebastian Hoelle for planning and conducting the experiments, data analysis and simulations.
