An Integrated Cooling System for Hybrid Electric Vehicle Motors: Design and Simulation

Hybrid electric vehicles offer the advantages of reduced emissions and greater travel range in comparison to conventional and electric ground vehicles. Regardless of propulsion strategy, efficient cooling of electric motors remains an open challenge due to the operating cycles and ambient conditions. The onboard thermal management system must remove the generated heat so that the motors and other vehicle components operate within their designed temperature ranges. In this article, an integrated thermal structure, or cradle, is designed to efficiently transfer heat within the motor housing to the end plates for transmission to an external heat exchanger. A radial array of heat pipes function as an efficient thermal connector between the motor and heat connector, or thermal bus, depending on the configuration. Cooling performance has been evaluated for various driving cycles. Numerical results show that 1.3 kW of peak heat wattage can be accommodated with free convection while 3.2 kW is obtained by adding forced convection using 13.7 W of electric power. The internal motor temperature is maintained within the prescribed limits of 75°C and 55°C values, respectively.