Abstract
The continuous derivation of the ambient temperature and cooling demand in CO2 refrigeration and air-conditioning systems equipped with multi-ejector modules for supermarkets requires the analysis of the fixed ejector utilisation in a very wide range of the operational envelope. Therefore, performance mapping of the four R744 ejectors installed in the multi-ejector pack was performed. The investigations of a single ejector's work were performed based on the proposed hybrid reduced-order model to predict the performance of each ejector under arbitrary operating conditions. The proposed model was validated and generated by use of the experimental data together with the computational fluid dynamic model results. The ejector efficiency mapping indicated the area of the best ejector performance in the range from approximately 50 bar–100 bar. The mass entrainment ratio of all four ejectors was presented for different ambient temperatures and the pressure lift. An area of the mass entrainment ratio greater than 0.3 was obtained by each ejector at ambient temperature above approximately 15 °C for pressure lift below 10 bar. The approximation functions of the ejector pressure lift in terms of the ambient temperature for air-conditioning operating conditions to reach the best efficiency of each ejector are proposed.