IIR document

Optimization of a transcritical N2O refrigeration/heat pump cycle.


Thermodynamic analyses as well as optimization studies based on the maximum cooling COP of transcritical nitrous oxide (N2O) refrigeration/heat pump cycle are presented in this article and the system performance is compared with that of a transcritical carbon dioxide (CO2) cycle. The performance improvement through the use of an internal heat exchanger and its effect on the optimum parameters for both cycles are also reported. In spite of the property similarity between the two natural refrigerants, the performances are modestly dissimilar. Transcritical N2O cycle yields moderately greater COP than a corresponding CO2 cycle (a maximum difference of 15.7% for the given range of study) and this performance improvement is more significant at lower gas cooler exit temperature and higher evaporator temperature. The transcritical N2O cycle is better than the CO2 cycle with respect to optimum system high side pressure, which is significantly lower with a maximum reduction of 19%. Transcritical N2O cycle also exhibits a lower discharge temperature and a lower compressor pressure ratio; however the volumetric capacity on an average is 9% lower than that of CO2. Effect of internal heat exchanger on both optimum discharge pressure and cooling COP is marginally more pronounced for the CO2 cycle (maximum COP improvement is 20.1% for N2O whereas it is 23.8% for CO2 and optimum discharge pressure reduces by 16.3% for the N2O system with a reduction of 19.4% for the CO2 system within the given operating range). This study concludes that the transcritical N2O cycle is better than its CO2 counterpart although the use f internal heat exchanger is less profitable. This could be an importantly favourable finding in the hunt for natural refrigerants which have reasonably good performance characteristics.

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Pages: 2008-2


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  • Original title: Optimization of a transcritical N2O refrigeration/heat pump cycle.
  • Record ID : 2009-0051
  • Languages: English
  • Source: 8th IIR-Gustav Lorentzen Conference on Natural Working Fluids (GL2008)
  • Publication date: 2008/09/07


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