Design and validation of a transcritical CO2 mobile refrigerated container system for military applications.

This paper describes the design and analysis of a transcritical CO2 (R744), multi-temperature, mobile refrigerated container system. The use of CO2 as a refrigerant has been widely applied to supermarket refrigeration systems in recent years and shown to be promising for other applications as well. However, the extreme operating conditions of this application (up to 57°C ambient temperature and frozen temperature of -20°C) make using CO2 as a refrigerant a unique challenge here. In order to achieve reasonable efficiency at the extreme conditions of this application, several improvements have been implemented: Multi-stage compression with intercooling, improved gas cooler performance with a microchannel heat exchanger, internal heat exchange, and expansion work recovery with an ejector. The results presented in this paper show that the very high ambient temperature of this system allows for very significant COP improvement using each of the above improvements methods (over 50 % combined improvement).