Electric Vehicle Cooling System. Comparison of Ethylene Glycol-Water and Fluorinert FC72

The cooling conditions of electric vehicles are completely different when compared to the cooling conditions of internal combustion engines for passenger cars, particularly the liquid flow rate and the coolant temperature. The electric vehicle has a flow rate of approximately 500 L/h at low coolant temperatures and the internal combustion engine may have a flow rate as high as 5 000 L/h at high coolant temperature. Without optimization the same size radiator for the heat dissipation for an internal combustion engine of 30 kW can only satisfy 3 kW of heat dissipation for the electric vehicle.

We have developed two solutions to cool the electric vehicle:

• A conventional cooling solution by using the same cooling liquid mixture, Ethylene Glycol-water 50-50%, that is to say, we adapted and optimized the cooling radiator for low flow rate and low coolant temperature.
• An evaporative cooling solution by using a new fluid, called, Fluorinert FC72. This new fluid has the boiling temperature of 56 °C at atmospheric pressure and is compatible with the electric vehicle specification.