Vehicle-level evaluation of an R290 secondary-loop integrated thermal management system with a CFD-calibrated 14-way valve model

Refrigerant regulations and the increasing adoption of multiport-valve-based integrated thermal management systems (ITMSs) have made architecture selection an important issue for battery electric vehicles (BEVs). This study evaluates the vehicle-level performance of an R290 secondary-loop ITMS employing a 14-way coolant valve on a common BEV platform. The valve hydraulics were characterized by computational fluid dynamics (CFD) and embedded into a one-dimensional model with mode-dependent pressure-drop characteristics. A reference R1234yf octovalve-based architecture and the proposed R290-based architecture were compared under hot and cold driving and DC fast-charging conditions, and an additional FV(R1234yf) case was included in the driving analysis to distinguish the structural effect of the secondary-loop architecture from the refrigerant effect of R290. The results show that the proposed architecture improved HVB thermal response under both hot- and cold-climate driving, reducing the HVB reference-temperature attainment time by 56.0% and 42.3%, respectively, compared with the reference architecture. The vehicle electric efficiency also increased by 13.0% under hot-climate driving and by 14.6% under cold-climate driving. Under DC fast-charging conditions, the proposed architecture shortened the charging time by 11.2% and 17.5% under hot- and cold-climate conditions, respectively, while slightly increasing charging efficiency. These improvements were further reflected in reduced annual operating cost and use-phase CO₂ emissions. Overall, the results indicate that the proposed secondary-loop architecture provides meaningful structural advantages in coolant-side thermal-path formation, with the greatest vehicle-level benefit achieved when it is combined with R290.