Experimental investigation of a transcritical CO2 system for simultaneous heating and cooling performance

To analyze the refrigeration and heating performance of the transcritical CO2 system, an experimental study was carried out. The effect of the operating conditions on heating and cooling performance was investigated. The experimental results showed that the mass flow rate significantly increased with the compressor rotational speed, while the both heating coefficient of performance and refrigeration coefficient decreased with the compressor rotational speed. It was because the compressor power, cooling and heating capacity all increased with the compressor rotational speed, while the growth rate of compressor power was greater than that of cooling and heating capacity. Besides, the heating coefficient of performance became smaller in cold conditions, as the mass flow rate decreased because of the reduction in suction refrigerant density. Even so, when the heat source temperature in the evaporator side was equal to -18 degrees C, not only the heating coefficient of performance is greater than 2.5, but also the system could provide enough heat. A new correlation of optimal discharge pressure was developed in this paper. Therefore, CO2 is suitable for replacing traditional refrigerants, and the experimental results can provide some guidance for designing a transcritical CO2 system.