Theoretical evaluation of cooling and heat-pump operation of an environmental test chamber using CO2 as refrigerant.

The introduction of the EU F-Gas Regulation results in a strict schedule for phase-down and a ban of synthetic high-GWP refrigerants. Small industry sectors like environmental simulation are affected as well. The refrigerants R404A and R507 will be banned for new installations in 2020. Recent announcements of supply constraints and a massive price increase led to the question whether or not new drop-in alternatives are available. CO2 is a well-known and future reliable alternative in various applications and comes into focus for the environmental test industry. This work proposes a concept for an environmental test chamber using CO2 as refrigerant. Typical test procedures require temperatures below and above ambient. Cooling as well as heating is therefore necessary. The proposed concept allows both cooling and heat-pump mode. Furthermore a system simulation was used for a comparison of the total energy consumption for a specific test procedure between a baseline electrically heated environmental test chamber with R452A and the proposed concept. The results show reduced energy consumption for heat-pump mode which allows heating in wide range of the temperature requirements. However, an additional electrical heater is still necessary to cover temperature above 60°C. The cooling mode of the proposed concept is comparable to the baseline cooling cycle with respect to energy consumption.