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The cooling system of an electric vehicle adopts an electric water pump. Since the lifespan of the battery is very sensitive to a very narrow temperature band, the cooling system provides key solutions. The electric water pump is a core component of the cooling system which satisfies performance and durability criteria. Since, a local hot spot of motor casing results in the degradation of motor lifespan, it is necessary to design the motor casing for effective heat rejection. In this study, two different motor casing designs are applied to reject the joule heating of the motor efficiently. The temperature distribution of each casing is investigated with an IR camera. The IR camera was used to identify the local hot spot where the heat was most generated in the pump. Since the joule heating is proportional to pump power, it is necessary to understand the operating characteristics of the electric water pump. The experimental apparatus includes a water reservoir, a bypass valve, pressure and temperature sensors, DAQ, and IR camera. The operating temperature is ranged from atmospheric temperature to 50°C. When the pump is operated with 25°C coolant, each experiment takes 1 hour for the steady-state conditions and maximum temperature up to 55 °C. Three different pump performance are investigated with two different pump casing. The coolant temperature is also changed from 25 °C to 50 °C. As a result, the local hot spot is strongly dependent to pump load and it is mainly observed near the cable connector. Since temperature distribution on the casing surface is also affected by local hot spots, it is necessary to optimize heat rejection by extended surface.

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