Abstract
The cooling performance and reliability of a transcritical CO2 cycle can be significantly improved by using a multi-stage compressor with gas injection because the CO2 cycle has a large pressure difference across a compressor. The objective of this study is to investigate the performance and operating characteristics of a two-stage CO2 cycle with gas injection. In this study, the performances of a two-stage CO2 cycle with gas injection (called as "two-stage gas injection cycle") were measured as the amount of refrigerant charge, first- and second-stage compressor frequencies, and first- and second-stage EEV openings were varied in the cooling mode operation. The cooling COP of the two-stage gas injection cycle was maximally enhanced by 16.5% over that of the two-stage non-injection cycle in the experiments. In addition, when the first- and second-stage EEV openings were increased, the compression ratio decreased and this in turn, improved the cooling COP of the two-stage gas injection cycle. However, when the first-stage EEV opening was increased, the mass flow rate through the evaporator decreased, and this in turn, decreased the cooling capacity of the two-stage gas injection cycle. Therefore, in the two-stage gas injection cycle, an optimum control of both EEV openings is required.
Original language | English |
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Pages (from-to) | 40-46 |
Number of pages | 7 |
Journal | International Journal of Refrigeration |
Volume | 32 |
Issue number | 1 |
DOIs | |
Publication status | Published - 2009 Jan |
Bibliographical note
Funding Information:This work was supported by the Ministry of Commerce, Industry and Energy.
Keywords
- Carbon dioxide
- Compression system
- Injection
- Measurement
- Performance
- Refrigeration system
- Transcritical system
- Two-stage system
ASJC Scopus subject areas
- Building and Construction
- Mechanical Engineering