Experimental measurements on the effect of a modulating ejector in a transcritical CO2 system.

The success of CO2 as a refrigerant in commercial refrigeration is due to several factors, including the technological evolution of carbon dioxide refrigeration systems. One of the most recent developments is the use of an ejector in on/off and modulating versions. The present paper studies a refrigeration unit equipped with double technology: modulating ejector and traditional booster system. Experimental tests were carried out to measure and analyze the effect of the modulating ejector in the transcritical CO2 booster compressor rack. The tests were performed by measuring the external conditions, the main thermodynamic parameters of the unit and the power absorbed by the unit. The main objective of the investigation is the study of the energy efficiency comparison between the standard transcritical operation mode with parallel compression and the ejector operation mode. Measurements of the energy consumption for the two technologies were performed for more than five months. An estimation of the annual energy saving was calculated based on measured data. A theoretical model was developed to simulate the cycles with and without ejector.