Investigation on the adaptivity of the transcritical CO2 refrigeration system with a capillaryÉtude sur l'adaptabilité d'un système frigorifique au CO2 transcritique équipé d'un tube capillaire

•A capillary tube based transcritical CO2 refrigeration system was theoretically and experimentally discussed.•The studied system behaved similar to an EEV based system on performance comparison.•The performance in the capillary based system reached up to 98% of that in the EEV based system.•The studied system showed that the capillary is promising under test conditions.

In order to research the adaptivity of the capillary tube in the transcritical CO2 refrigeration system, a separated flow model of a CO2 capillary in which the metastable phenomenon was taken into consideration was built in the simulation of transcritical CO2 refrigeration system, and related experiments were carried out by a plant under different gas-cooler outlet temperatures. The performances of the capillary based system were further compared with that of the EEV (electronic expansion valve) based system. The results showed that the relative COP ranged from 82% to 98% when there was a 10 °C deviation between the real gas-cooler outlet temperature and the design value. Thus the capillary based transcritical CO2 system is promising and could achieve performance close to that of EEV based system in a wide range of gas-cooler outlet temperature.