The comprehensive research on the transcritical CO₂ thermal management system used in thermostatic transport vehicles

Natural fluid CO₂ has become the preferred target of refrigerant alternative in the electrified transportation field in recent years to replace positive temperature coefficient (PTC) heaters, reduce energy consumption, and respect the international ban on Hydrofluorocarbons (HFCs) refrigerants. Thermostatic transport vehicles (TTVs) are well suited to exploit the benefits of CO₂ due to their working conditions with a broad range of ambient temperatures, extensive transit distances, and substantial heating capacity requirements in cold climates. In this paper, a transcritical CO₂ heat pump air-conditioning system used in TTV was constructed initially with proper control logic. Then following the assessment of the system's steady-state performance, the dynamic operation process under high thermal inertia was thoroughly examined and analyzed in detail. Ultimately, the optimization of the dynamic response process was realized under varying heat flow boundary conditions. The primary results demonstrated that the rationally designed CO₂ thermal management system performed admirably in various operating conditions, particularly in the heating mode where the coefficient of performance (COP) exceeded 3.2. Addressing the high-frequency fluctuation caused by the cargo thermal inertia, the temperature could be maintained with only two starts and stops within 3×10⁵ seconds when the system control logic was refined. The optimized thermal management system of TTV efficiently allowed cargo to achieve the proper temperature as quickly as possible and sustain stability. This study provides an effective theoretical basis for the promotion of the transcritical CO₂ thermal management system in the field of TTVs.