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

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

Type of article: Article

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 9.5 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 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. A visualization experiment revealed that the oil near the tube wall became an obstacle for the heat transfer coefficient and the distribution of oil changed according to the CO2 velocity and density variation due to its temperature variation.

Details

  • Original title: Cooling heat transfer characteristics of CO2 and CO2-oil mixtures under supercritical pressure conditions.
  • Record ID : 2004-2112
  • Languages: English
  • Source: Transactions of the Japan Society of Refrigerating and Air Conditioning Engineers - vol. 20 - n. 3
  • Publication date: 2003
  • Document available for consultation in the library of the IIR headquarters only.

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