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Two-phase flow pattern, heat transfer, and pressure drop in microchannel vaporization of CO2.

Author(s) : PETTERSEN J.

Summary

The heat-transfer coefficient and pressure drop were measured for flow vaporization of CO2 in an extruded microchannel tube with 25 channels that were 0.81 mm in diameter and 0.5 m in length. The test section was heated by a water jacket, and a regression method was used to derive the internal heat-transfer coefficient based on the measured overall heat-transfer coefficient. Two-phase flow patterns were visualized in a separate test rig, using a 0.98 mm heated glass tube and a high-speed digital camera. Wavy annular flow with entrainment dominated at high mass flux. Flow pattern observations did not fit generalized maps. Heat-transfer measurements were conducted at varying mean vapour fractions at temperatures of 0 to 25 °C, mass flux of 190 to 570 kg/m.s, and heat flux of 10 and 20 kW/m. Heat-transfer results show significant influence of dryout, particularly at high mass flux and high temperature. Nucleate boiling dominates prior to dryout. Frictional pressure drop data were correlated with a mean deviation of 16% using an existing model developed for vertical flow. Heat transfer data were correlated with a combination of models for nucleate boiling, convective evaporation, dryout incipience, and post-dryout heat transfer.

Details

  • Original title: Two-phase flow pattern, heat transfer, and pressure drop in microchannel vaporization of CO2.
  • Record ID : 2005-1135
  • Languages: English
  • Source: ASHRAE Transactions. 2003 Winter Meeting, Chicago, Illinois. Volume 109, part 1 + CD-ROM.
  • Publication date: 2003

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