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Flow patterns and heat transfer characteristics of flow boiling of CO2 and oil mixtures in horizontal smooth and micro-fin tubes.

Author(s) : GAO L., ONO T., HONDA T.

Summary

Experiments on flow patterns and flow boiling heat transfer of pure CO2 and CO2-oil mixtures in horizontal smooth and helical grooved micro-fin tubes have been carried out. The smooth tube is a stainless steel tube, 3.76 mm in inner diameter, and the micro-fin tube is a copper tube, 3.75 mm in mean inner diameter. Experiments were conducted at mass velocities from 100 to 380 kg/(m2s), saturation temperature of 10°C, heat fluxes from 10 to 30 kW/m2, and oil circulation ratio from 0 to 1.0 mass%. For the smooth tube, the flow patterns were observed, and the results were compared with the flow pattern map developed by Cheng et al., and the heat transfer coefficient in pre-dryout region increases with the increase in heat flux in case of pure CO2. These results indicate that the flow boiling heat transfer is dominated by nucleate boiling. The heat transfer coefficient decreases slightly with the increase in vapour quality at high heat flux conditions. This tendency is considered due to the partial dryout occurred on the upper perimeter of the tube. In case of CO2-oil mixtures, the heat transfer coefficient in pre-dryout region decreases significantly than that of pure CO2. The flow patterns and heat transfer coefficients in the micro-fin tube were compared with those for the smooth tube.

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Pages: 2008-2

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Details

  • Original title: Flow patterns and heat transfer characteristics of flow boiling of CO2 and oil mixtures in horizontal smooth and micro-fin tubes.
  • Record ID : 2009-0079
  • Languages: English
  • Source: 8th IIR-Gustav Lorentzen Conference on Natural Working Fluids (GL2008)
  • Publication date: 2008/09/07

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