CFD Study of Optimal Under-hood Flow for Thermal Management of Electric Vehicles

Abstract

To improve fuel economy of conventional vehicles and the driving range of electric vehicles, reducing the aerodynamic drag is of particular interest. As electric vehicles typically have lower cooling power requirement, reducing the aerodynamic drag induced by cooling air is of utter importance. This study investigates alternative under-hood cooling flow solutions, with the target of reducing cooling drag for battery electric vehicles (BEV). Two different approaches of positioning the vehicle’s heat exchangers (in series and in parallel) with a number of different air inlet and outlet configurations have been evaluated using CFD simulations. The geometry of the open grille DrivAer Model have been used to a large extent in this work, including a simplified electric powertrain and an alternative cooling module. For this work, a Reynolds-Averaged Navier-Stokes (RANS) method utilizing the k-" turbulence model have been implemented in the commercial CFD software STAR-CCM+. The results show that a similarly low cooling drag can be obtained from positioning heat exchangers both in series and in parallel. When heat exchangers are positioned in parallel, the results indicate high mass flow rate and low drag potential for side positioned inlets including air outlets located at the front arc of the wheel houses. Furthermore, results indicate that low positioned air inlets are more drag efficient than those positioned higher on the front bumper. The results of this study should serve as an suggestion towards under-hood cooling flow solutions for battery electric vehicles.