Dynamic trade-off balancing and energy savings in battery-cabin coupled CO₂ EVTMS via semi-series refrigerant direct cooling architecture

With the rapid adoption of electric vehicles, electric vehicle thermal management systems (EVTMS) face pressing challenges in dynamic battery temperature uniformity control and coupling with the passenger compartment. Based on the vehicle thermal demands, a transient model of the EVTMS that uses refrigerant direct cooling for the battery was developed and validated. The dynamic cooling performance and cell-to-cell temperature uniformity of two system architectures with unequal evaporation pressure (UEP) and equal evaporation pressure (EEP) were compared under different control schemes. The suitability of each architecture and control approach was then analyzed. The performance degradation caused by branch mixing under fixed constraints and the corresponding mechanisms are elucidated. Furthermore, the trade-off between battery cooling and cabin thermal management was characterized, and the extent of the mutual influence was quantified. To address branch mixing-induced performance degradation and the trade-off between battery uniformity and cabin comfort, a novel semi-series direct cooling architecture with a temperature following control strategy is proposed. Simulation results indicate that this approach can reduce the battery’s maximum temperature difference by 60%, lower average power consumption by 3%, and maintain cabin comfort. The findings offer new theoretical and methodological guidance for co-optimizing architecture and control in CO₂ direct cooling EVTMS for engineering applications.