Modelling the performance of a new cooling unit for refrigerated transport using carbon dioxide as the refrigerant

This paper provides a theoretical assessment of the thermal performance of a new CO 2 vapour- compression system for refrigerated transport applications. Three different configurations are investi- gated: the standard back-pressure with low pressure receiver lay-out and two arrangements integrating a two-phase ejector. In particular, the use of an auxiliary evaporator in the outlet line of the ejector is considered, to extend the ejector operating range. A numerical model of the system is developed and its theoretical performance is discussed for different values of internal space temperature and external am- bient temperature. Simulations’ results show that the ejector cycle configuration is convenient when the system is operating in a hot climate with a maximum COP increase (compared to the traditional config- uration) equal to 15.9%, at 42 °C ambient temperature and -5 °C internal space temperature. The use of an auxiliary evaporator can extend the operating range of the ejector to lower values of ambient tem- perature, with a maximum COP improvement (over the traditional configuration) equal to 21.0% at 25 °C ambient temperature and 5 °C internal cargo space.