Visualization of two-phase refrigerant and refrigerant-oil flow in a microchannel

Brandon S. Field, Pega Hrnjak

Research output: Chapter in Book/Report/Conference proceedingConference contribution


Visualizations of adiabatic two-phase refrigerant flow in a glass channel of diameter 0.5 mm have been made for three refrigerants: R134a, Propane (R290), and Ammonia (R717), representing a wide span of fluid properties, which covers most of the refrigerants commercially in use. In these visualizations four flow regimes were observed: Bubble-slug, slug, slug-annular, and annular. These flow regimes were compared to various flow maps, including some developed for small channels. Flow visualizations were also made with mixtures of R134a and 68-weight POE oil at oil circulation rates of approximately 0.5, 1.5 and 3 percent. This is of interest when considering refrigeration systems, which have a small percentage of oil in circulation that travels through system and through the heat exchangers. When the refrigerant is in a liquid state, this presents little variation in fluid properties, because the concentration is so small. However, when the refrigerant is partly vapor, the oil concentration in the remaining liquid can have significant effect on the fluid properties. In addition, the saturation temperature and pressure of the oil-refrigerant mixture changes with concentration, where a single-phase vapor is never observed in flows of oil-refrigerant mixtures, even at temperatures exceeding the saturation temperature of the pure mixture. This effect is known as "apparent superheat."

Original languageEnglish (US)
Title of host publicationHeat Transfer, Fluid Flows, and Thermal Systems
PublisherAmerican Society of Mechanical Engineers (ASME)
Number of pages10
ISBN (Electronic)0791843025
StatePublished - 2007
EventASME 2007 International Mechanical Engineering Congress and Exposition, IMECE 2007 - Seattle, United States
Duration: Nov 11 2007Nov 15 2007

Publication series

NameASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE)


OtherASME 2007 International Mechanical Engineering Congress and Exposition, IMECE 2007
Country/TerritoryUnited States

ASJC Scopus subject areas

  • Mechanical Engineering
  • General Engineering


Dive into the research topics of 'Visualization of two-phase refrigerant and refrigerant-oil flow in a microchannel'. Together they form a unique fingerprint.

Cite this