Energy analysis of CO2 refrigeration systems using measured values of compressor efficiency.

The strong demand for phasing out high GWP refrigerants has pushed research towards the study of other sustainable alternatives like natural refrigerants and in particular carbon dioxide. Because of CO2 low critical point, when the ambient temperature is high the cycle has to work in a transcritical configuration. This leads to a different operation mode, potentially with higher losses and consequently lower performances. The purpose of this paper is to study two different solutions and their performance during the transcritical operation and see which one can perform better from the yearly analysis point of view. Transcritical booster system and transcritical booster with parallel compression system will be analysed, with and without heat recovery for sanitary hot water production and space heating. Temperature data in Milano (Italy) and Valéncia (Spain) are considered for the external conditions; measured values of compressor efficiency are used for the analysis.