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Entropy 2018, 20(1), 31;

Energetic and Exergetic Analysis of a Transcritical N2O Refrigeration Cycle with an Expander

State Key Laboratory of Multiphase Flow in Power Engineering, Xi’an Jiaotong University, Xi’an 710049, China
Department of Mechanical Engineering, University of Minnesota, Minneapolis, MN 55455, USA
Author to whom correspondence should be addressed.
Received: 6 December 2017 / Revised: 31 December 2017 / Accepted: 4 January 2018 / Published: 18 January 2018
(This article belongs to the Special Issue Phenomenological Thermodynamics of Irreversible Processes)
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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. View Full-Text
Keywords: N2O; transcritical refrigeration cycle; COP; exergy analysis N2O; transcritical refrigeration cycle; COP; exergy analysis

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Zhang, Z.; Hou, Y.; Kulacki, F.A. Energetic and Exergetic Analysis of a Transcritical N2O Refrigeration Cycle with an Expander. Entropy 2018, 20, 31.

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