Quantitative evaluation of the evaporator configuration’s implications on the performance enhancement in CO₂ thermal management system for electric vehicle.

Enhancing the cooling performance of CO2 thermal management systems in electric vehicles remains a critical research focus. Although multi-path evaporators improve thermal efficiency by increasing the evaporative temperature, their associated pressure drop reduces compressor suction pressure, presenting a key trade-off in system performance. To investigate this coupled problem, a mathematical model of CO2 thermal systems with varying evaporator configurations was developed, and an experimental test bench was established to analyze their impact on comprehensive performance. The effect of the evaporator pass on the cooling performance under different operating conditions was firstly studied, which both involved the influence of the heat transfer enhancement and pressure drop. Moreover, the evaporative pressure, suction pressure and the mean temperature were analyzed to reveal the dominating parameters under different conditions. An optimized heat exchanger configuration was concluded (which gained a 34.5 % COP increment with a 9.4 % bigger cooling capacity at 35 ◦C ambient), and it was further validated by the experimental investigations. Finally, experimental comparison was conducted for thermal management systems with different exchanger configurations. The results showed that the evaporator had an optimal pass under larger cooling capacities requirement, but the performance was always increased with the evaporator pass under a smaller cooling capacity. The pressure drop had a dominating effect for the larger cooling capacities operation conditions, and the evaporator required different design for a better performance according to the maximum cooling demand. It could provide a reference of the better system design for different types of electric vehicles.