Performance of a CO2 based transcritical air conditioning system under summer and winter conditions

• Published in: Thermal science and engineering progress Vol. 41; p. 101847
• Main Authors: Kumar Sharma, Devendra, Saikiran Pegallapati, Aaditya, Ramgopal, Maddali
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.06.2023
• Subjects: Air conditioning system; Compact VCRS; Experimental results; Transcritical/subcritical CO2 cycle; Transcritical/subcritical CO2 cycle; Air conditioning system; Compact VCRS; Experimental results
• ISSN: 2451-9049; 2451-9049
• DOI: 10.1016/j.tsep.2023.101847

•CO2 based summer air conditioning unit is studied under low ambient temperature, winter conditions.•Effect of gas cooler air flow rate on transition of cycle is studied.•Gas cooler/condenser exit temperature variation is marginal with air flow rate.•System designed for summer conditions performs well under winter conditions also.•Gas cooler air flow rate can be used as a control parameter for transition. Experimental studies are carried out on a CO2 based transcritical system designed for air conditioning applications. A fully instrumented test rig that consists of a semi-hermetic compressor, finned tube evaporator and gas cooler, electronic expansion valve, accumulator and receiver is developed for this purpose. The system is designed for 35 °C ambient temperature as per the standards. Same system is tested under low ambient temperature for cooling performance. Results show that depending upon the available low ambient air temperature, the system operates either in subcritical mode or transcritical mode near critical point. Further, heat rejection process can be shifted across critical point with the help of gas cooler/condenser air flow rate. This can help in developing control strategy for high side pressure for the application of simultaneous space heating and cooling in low temperature ambient conditions. Evaporator temperature is found to drop significantly in low ambient temperature conditions indicating that frosting of evaporator could be a practical issue. Cooling performance of the system in low ambient temperature conditions is found to be better than the summer season cooling performance.