A PERFORMANCE COMPARISON OF FIXED EJECTORS WITH AND WITHOUT A SWIRL GENERATOR AND CONTROLLABLE EJECTORS IN A CO_2 REFRIGERATION SYSTEM

摘要

This paper provides a performance comparison ejector technology to be installed in a CO_2 supermarketrnrefrigeration system. Namely, the fixed ejectors with and without swirl flow at the inlet of the motive andrnsuction nozzles and the fixed and controllable ejectors equipped with convergent and convergent-divergentrnnozzles and were analysed. The Coefficient of Performance (COP) of the ejector-based refrigeration system isrndependent on the design and control of the mass flow rate through this device. The literature suggests that onernof the possible ejector efficiency improvements can be performed using a swirl generator at the inlet of thernmotive nozzle. Therefore, a swirl generator was simulated for different size CO_2 ejectors under typicalrnoperating conditions in a supermarket and for a range of rotational speeds. In addition, the performance of arngroup of fixed ejectors working in parallel was compared with two controllable ejectors with a needle. Tornanalyse the potential of the considered approaches, the device performance was numerically simulated usingrnthe validated Homogeneous Equilibrium Model (HEM) model for the same typical transcritical parameters.rnFor all the fixed ejectors with and without the swirl generator, devices of various sizes were simulated andrncompared with the corresponding controllable ejector performance at a few needle positions. For both ejectorrntypes, a global efficiency as a function of the mass flow rate was presented and discussed.