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Optical investigation of R134a two-phase flows in a microchannel.

Author(s) : REVELLIN R., THOME J. R.

Summary

An optical measurement method for two-phase flow characterization in microtubes has been applied to determine the frequency of bubbles exiting a micro-evaporator, the coalescence rates of these bubbles and their lengths as well as their mean two-phase vapour velocity. The tests were run in a 0.5 mm diameter glass channel using R134a at 26, 30 and 35 °C saturation temperatures. Four flow patterns (bubbly flow, slug flow, semi-annular flow and annular flow) with their transitions (bubbly/slug flow and slug/semi-annular flow) were detected. The two-phase flow pattern transitions observed with R134a did not compare well to a leading microscale flow map for refrigerants nor to a microscale map for air-water flows. No significant influence of the inlet subcooling (2, 3, 5 °C) nor the saturation pressure has been observed on the flow pattern transitions. Furthermore, changing the heated length from 70 to 30 mm before the glass tube did not influence the location of the transition lines.

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Pages: 2005-3

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Details

  • Original title: Optical investigation of R134a two-phase flows in a microchannel.
  • Record ID : 2006-0666
  • Languages: English
  • Source: Commercial Refrigeration. Thermophysical Properties and Transfer Processes of Refrigerants. Proceedings of the IIR International Conferences.
  • Publication date: 2005/08/02

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