Numerical Thermal Modelling of Multiphase Spray Cooling of Hairpin Windings

This paper describes the methodology adopted for the numerical thermal modelling of both submerged jets (single phase) and nebulized jets (multi-phase) used for the cooling of hairpin type end-windings. The work highlights the challenges arising when modelling discrete phases using computational fluidynamics (CFD) and proposes a setup for effectively capturing the physics whilst maintaining an acceptable level of computational cost of the simulations involving multi-phase cases. Additionally, a comparison of the cooling performance of the two strategies is carried out by observing the convective phenomena. Indeed, despite the overall lower fluid velocity achieved, the single-phase case shows an heat transfer rate double compared to the spray cooling and more uniform temperature distribution all over the winding surface thanks to the bigger level of penetration through the gaps in between the conductors.