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Entropy 2015, 17(4), 2544-2555; doi:10.3390/e17042544

Thermodynamic Analysis of Double-Stage Compression Transcritical CO2 Refrigeration Cycles with an Expander

Institute of Architecture and Civil Engineering, North China University of Science and Technology, Tangshan 063009, China
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Author to whom correspondence should be addressed.
Academic Editor: Kevin H. Knuth
Received: 17 March 2015 / Revised: 13 April 2015 / Accepted: 15 April 2015 / Published: 22 April 2015
(This article belongs to the Section Thermodynamics)
View Full-Text   |   Download PDF [941 KB, uploaded 22 April 2015]   |  

Abstract

Four different double-compression CO2 transcritical refrigeration cycles are studied: double-compression external intercooler cycle (DCEI), double-compression external intercooler cycle with an expander (DCEIE), double-compression flash intercooler cycle (DCFI), double-compression flash intercooler cycle with an expander (DCFIE). The results showed that the optimum gas cooler pressure and optimum intermediate pressure of the flash intercooler cycles are lower than that of the external intercooler cycle. The use of an expander in the DCEI cycle leads to a decrease of the optimum gas cooler pressure and little variation of the optimum intermediate pressure. However, the replacement of the throttle valve with an expander in the DCFI cycle results in little variation of the optimal gas cooler pressure and an increase of the optimum intermediate pressure. The DCFI cycle outperforms the DCEI cycle under all the chosen operating conditions. The DCEIE cycle outperforms the DCFIE cycle when the evaporating temperature exceeds 0 °C or the gas cooler outlet temperature surpasses 35 °C. When the gas cooler exit temperature varies from 32 °C to 48 °C, the DCEI cycle, DCEIE cycle, DCFI cycle and DCFIE cycle yield averaged 4.6%, 29.2%, 12.9% and 22.3% COP improvement, respectively, over the basic cycle. View Full-Text
Keywords: CO2 transcritical refrigeration cycle; double-stage compression; expander; coefficient of performance; intercooler CO2 transcritical refrigeration cycle; double-stage compression; expander; coefficient of performance; intercooler
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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MDPI and ACS Style

Zhang, Z.; Tong, L.; Wang, X. Thermodynamic Analysis of Double-Stage Compression Transcritical CO2 Refrigeration Cycles with an Expander. Entropy 2015, 17, 2544-2555.

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