Experimental study and performance evaluation of R744 thermal management systems with enhanced parallel cooling for electric vehicles

As worldwide environmental concerns grow, R744 (CO₂) has become one of the preferred refrigerants in electric vehicle (EV) thermal management system due to its environmentally friendly characteristics. This study presents the development and evaluation of an Enhanced Parallel Cooling (EPC) system, a novel advancement designed to optimize the performance of R744 thermal management systems in EVs. A series of experiments are carried out to investigate the effects of key operating variables such as the coolant flow rate, and air velocity on the system efficiency. Meanwhile, Response Surface Methodology (RSM) is employed to determine the optimal control contour map under various environmental conditions. The maximum cooling capacity of the EPC system in supercharging mode is experimentally evaluated. Furthermore, a comparative analysis of driving range improvement under the Urban Dynamometer Driving Schedule (UDDS) and the Highway Fuel Economy Test (HWFET) cycles is carried out. With the help of the Series Cooling Unit (SCU) in the EPC system, the maximum cooling capacity increases by 27.8 % to 9.89 kW, and the driving range increases by up to 14.6 km. The findings underscore the potential of the innovative R744 thermal management system architecture to improve operational efficiency and extend the driving range of EVs.