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Flow boiling heat transfer characteristics of CO2 and CO2-oil mixtures in a horizontal smooth thin tube.

Number: pap. D2-035

Author(s) : GAO L., WATANABE Y., SATO M., et al.

Summary

Experiments on flow boiling heat transfer of pure CO2 and CO2-oil mixtures in a horizontal smooth thin tube were carried out. The test tube is a stainless steel smooth tube, which is 2.0 mm in inner diameter and 1 m in length. Experiments were conducted at mass velocities from 380 to 1500 kg/(m2s), a saturation temperature of 10°C, heat fluxes from 10 to 40 kW/m2, and the oil circulation ratios from 0 to 0.97 mass%. The measured heat transfer coefficients, dryout inception and completion qualities were compared with those calculated from the prediction model developed by Cheng et al. in both cases of pure CO2 and CO2-oil mixtures. As the results, in both cases of CO2 and CO2-oil mixtures, the observed flow patterns correspond well with the flow pattern map presented by Cheng et al. In the case of pure CO2 at pre-dryout region, the measured local heat transfer coefficients were slightly lower than predicted values calculated from prediction model presented by Cheng et al., and prediction methods agree with 87.6% of the experimental results within ± 30 %. In the case of CO2-oil mixtures, the measured local heat transfer coefficients were much lower than those of pure CO2. The result is considered due to the nucleate boiling being suppressed by the oil film. And it found that the dryout inception and completion qualities decrease with the increase in mass velocity. On the other hand, the dependence of the dryout qualities on heat flux is not clear.

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Pages: 6 p.

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Details

  • Original title: Flow boiling heat transfer characteristics of CO2 and CO2-oil mixtures in a horizontal smooth thin tube.
  • Record ID : 30005395
  • Languages: English
  • Source: ACRA2010. Asian conference on refrigeration and air conditioning: Tokyo, Japan, June 7-9, 2010.
  • Publication date: 2010/06/07

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