The heat generated by an electric motor is due to losses in the stator or rotor windings. A promising cooling technique is to inject a dielectric liquid directly onto the hot solid parts. To design such a cooling system, it is necessary to estimate the heat transfer coefficients between the solid parts and the cooling liquid film that flows over them. The main objective of the project is to improve heat transfer modelling for direct injection of coolant into electric motors. To achieve this, we propose to develop a multi-scale modelling strategy based on both numerical and experimental studies. We will study the heat transfer when a cold liquid jet impacts and then flows as a film over a hot solid with a complex surface. We will also develop a modelling strategy to handle the two-phase flow regime transitions resulting from the interactions between the liquid injection and the rotor motion. Finally, we will apply this new modelling strategy to estimate the heat transfer in a real electric motor.