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Optimal heat rejection pressure of CO2 heat pump water heaters based on pinch point analysis.

Author(s) : CHEN Y. G.

Type of article: Article, IJR article

Summary

The control of heat rejection pressure is of great importance for transcritical CO 2 heat pump water heaters. However, almost all the existing correlations of optimal heat rejection pressure are based on an assumption of constant CO 2 exit temperature from gas cooler when changing the high-side pressure. Actually, pinch effect occurring in CO 2 gas cooler would have great impacts on CO 2 exit temperature as the high-side pressure varies, which in turn affects overall system performance. A cycle simulation model was developed in the present study incorporating pinch point analysis for gas cooling process. The model is independent on heat exchanger geometry parameters, which guarantees the generality of the model. Sensitivity analyses of main impact factors were conducted in detail including inlet and outlet water temperature, refrigerant evaporation temperature and superheat degree, pinch temperature difference and isentropic efficiency of compressor. Furthermore, a new correlation of optimal heat rejection pressure was proposed.

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Pages: 592-603

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Details

  • Original title: Optimal heat rejection pressure of CO2 heat pump water heaters based on pinch point analysis.
  • Record ID : 30027025
  • Languages: English
  • Source: International Journal of Refrigeration - Revue Internationale du Froid - vol. 106
  • Publication date: 2019/10
  • DOI: http://dx.doi.org/10.1016/j.ijrefrig.2019.04.003

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