The paper describes the experimental evaluation of a transcritical R744 system designed to serve in amulti-temperature refrigerated container unit. The high ambient temperatures often encountered in thisapplication, especially for a fluid like CO_2, require careful attention to compressor selection and gas coolerdesign. To evaluate different compressor options, a laboratory breadboard CO_2 system was used to test asingle-stage compressor compared to an enhanced system with multi-stage compression and intercoolerplus an ejector for improved evaporator performance and pressure lift. The results of the experimentalevaluation show that the single-stage compression system is limited to an ambient temperature of about40°C, while the multi-stage compression system is able to operate with sufficient capacity at ambienttemperature in excess of 50°C. Also presented is the actual prototype CO_2 refrigerated container unit to beevaluated.
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