Energetic and exergetic analysis of a transcritical N2O refrigeration cycle with an expander

Ze Zhang; Yu Hou; Francis A. Kulacki

doi:10.3390/e20010031

Energetic and exergetic analysis of a transcritical N₂O refrigeration cycle with an expander

Ze Zhang, Yu Hou, Francis A. Kulacki

Mechanical Engineering

Research output: Contribution to journal › Article › peer-review

5 Scopus citations

Abstract

Comparative energy and exergy investigations are reported for a transcritical N₂O refrigeration cycle with a throttling valve or with an expander when the gas cooler exit temperature varies from 30 to 55 °C and the evaporating temperature varies from -40 to 10 °C. The system performance is also compared with that of similar cycles using CO₂. Results show that the N₂O expander cycle exhibits a larger maximum cooling coefficient of performance (COP) and lower optimum discharge pressure than that of the CO₂ expander cycle and N₂O throttling valve cycle. It is found that in the N₂O throttling valve cycle, the irreversibility of the throttling valve is maximum and the exergy losses of the gas cooler and compressor are ordered second and third, respectively. In the N₂O expander cycle, the largest exergy loss occurs in the gas cooler, followed by the compressor and the expander. Compared with the CO₂ expander cycle and N₂O throttling valve cycle, the N₂O expander cycle has the smallest component-specific exergy loss and the highest exergy efficiency at the same operating conditions and at the optimum discharge pressure. It is also proven that the maximum COP and the maximum exergy efficiency cannot be obtained at the same time for the investigated cycles.

Original language	English (US)
Article number	31
Journal	Entropy
Volume	20
Issue number	1
DOIs	https://doi.org/10.3390/e20010031
State	Published - Jan 1 2018

Bibliographical note

Funding Information:
Acknowledgments: This work was supported by a scholarship from the China Scholarship Council while the first author was a visiting scholar at the University of Minnesota-Twin Cities and the Fundamental Research Funds for the Central Universities of China.

Publisher Copyright:
© 2018 by the authors.

Keywords

COP
Exergy analysis
NO
Transcritical refrigeration cycle

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abstract = "Comparative energy and exergy investigations are reported for a transcritical N2O refrigeration cycle with a throttling valve or with an expander when the gas cooler exit temperature varies from 30 to 55 °C and the evaporating temperature varies from -40 to 10 °C. The system performance is also compared with that of similar cycles using CO2. Results show that the N2O expander cycle exhibits a larger maximum cooling coefficient of performance (COP) and lower optimum discharge pressure than that of the CO2 expander cycle and N2O throttling valve cycle. It is found that in the N2O throttling valve cycle, the irreversibility of the throttling valve is maximum and the exergy losses of the gas cooler and compressor are ordered second and third, respectively. In the N2O expander cycle, the largest exergy loss occurs in the gas cooler, followed by the compressor and the expander. Compared with the CO2 expander cycle and N2O throttling valve cycle, the N2O expander cycle has the smallest component-specific exergy loss and the highest exergy efficiency at the same operating conditions and at the optimum discharge pressure. It is also proven that the maximum COP and the maximum exergy efficiency cannot be obtained at the same time for the investigated cycles.",

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