A novel and efficient CO2 gas cooler/condenser for a refrigeration application: A case study on supermarket refrigeration

A CO2 gas cooler/condenser integrated with an indirect evaporative cooler (dewpoint cooler) (DPCO2) has been installed into a CO2 refrigeration and air-conditioning system in one of the major supermarkets in Adelaide. The DPCO2 coolers along with the transcritical CO2 (TCO2) refrigeration rack were fitted with monitoring equipment and the data were monitored for a period of nine months, from June 2023 to April 2024.

This presentation details the findings of the monitoring, comparison with the validated model, and comparison with a system with a chill-boost adiabatic gas cooler/condenser. Over the nine-month test period, the DPCO2 cooler effectively allowed the refrigeration system to operate in its subcritical cycle almost all the time. The outliers were when the DPCO2 cooler was deactivated for baseline testing, and when the moisture content was high and the dewpoint temperature depression was very low.

On January 23, 2024, a maximum temperature of 41.5oC was recorded in Adelaide. On this day, the DPCO2 system remained subcritical and operated at the maximum condensing temperature of 26oC. The chill-boost adiabatic gas cooler would have operated in a transcritical cycle for the majority of the time on the same date.

The monitored data are found to be in line with the predicted outcome; the difference between modeled and monitored energy consumption is less than 1 per cent. The monitored data demonstrated that using a DPCO2 system instead of a chill-boost gas cooler results in annual energy savings of 11 per cent and a 20 per cent peak demand power reduction.

This monitoring outcome shows that the integration of a dewpoint cooler into a refrigeration system in supermarkets helps the system run efficiently in its subcritical cycle for the majority of the time if dewpoint temperatures are below 22oC.