CO2, Ejector, Vapor Injection
In the recent years, Transcritical CO2 refrigeration is gaining popularity. However, operation above critical point at higher ambient temperatures results in significant reduction of CO2 refrigeration cycle efficiency. Vapor injection and ejector are probably the mostly widely applied transcricial cycle enhancement options. The proposed paper includes a description of a simple transcritical one dimensional model of an ejector, based on real gas properties (accessible through Refprop), as well as integration of this model in a refrigeration cycle. Vapor injection cycle is analyzed based on compressor performance and its ability to digest vapor injection stream. An enhancement of traditional compressor performance approximation, enabling to include the vapor injection stream, is presented and vapor injection cycle is analyzed based on that compressor model. Comparison of CO2 cycle performance between two outlined methods at different operation conditions is presented.