Theoretical and experimental studies are carried out on a transcritical CO₂ based air-conditioning unit. Two configurations– a system with single-stage expansion (SSE) and a system with two-stage expansion (TSE) have been considered. Detailed numerical models have been developed for both configurations. Results obtained from numerical simulations are compared with experimental results. The performance of the system with single-stage expansion is compared with two-stage expansion under different conditions of refrigerant charge, receiver volume, and ambient temperature. Both numerical and experimental results show that the SSE configuration is highly sensitive to refrigerant charge as compared to the TSE configuration. The TSE configuration offers better system controllability provided the receiver is sized properly. Besides, it is found that for the same performance, the required charge can be reduced by about 15% for the TSE configuration as compared to the SSE configuration.

在跨临界CO ₂上进行了理论和实验研究基地的空调机组。已经考虑了两种配置-具有单阶段扩展（SSE）的系统和具有两阶段扩展（TSE）的系统。已经针对这两种配置开发了详细的数值模型。从数值模拟获得的结果与实验结果进行比较。在制冷剂进料，接收器体积和环境温度不同的条件下，将单级膨胀系统的性能与两级膨胀进行了比较。数值和实验结果均表明，与TSE配置相比，SSE配置对制冷剂充注高度敏感。如果接收器尺寸合适，TSE配置可提供更好的系统可控制性。此外，发现对于相同的性能，