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Cooling heat transfer characteristics of CO2 and a CO2-oil mixture under supercritical pressure conditions.

Author(s) : MORI K., ONISHI J., SHIMAOKA H., et al.

Summary

In order to obtain the data for designing and optimizing air-conditioning systems using a CO2 refrigerant, the cooling heat transfer characteristics of CO2 were examined at a supercritical pressure condition of 9 MPa and temperatures between 20 and 70°C. The data obtained revealed that the heat transfer coefficient increased with mass flux and the maximum heat transfer coefficients were obtained at 45°C. Two layer models for flow field near the tube wall were proposed: the model was found to be valid according to the comparison of the predicted values with the measured data. A CO2-oil mixture was also investigated, and was found to exhibit lower heat transfer coefficients than CO2 alone, particularly in the range of 40-55°C. A visualization experiment revealed that the oil near the tube wall became an obstacle for heat transfer coefficient and the distribution of oil changed according to the CO2 density variation due to its temperature variation.

Details

  • Original title: Cooling heat transfer characteristics of CO2 and a CO2-oil mixture under supercritical pressure conditions.
  • Record ID : 2006-1141
  • Languages: English
  • Source: Green breeze from Asia: frontiers of refrigerants, heat transfer and system.. ACRA-2002. Proceedings of the Asian conference on refrigeration and air conditioning.
  • Publication date: 2002/12/04

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