Flow Boiling Visualization of R-134a in a Vertical Channel of Small Diameter
2010 (English)In: Journal of heat transfer, ISSN 0022-1481, Vol. 132, no 3, 031001- p.Article in journal (Refereed) Published
The present work reports on flow boiling visualization of refrigerant R-134a in a vertical circular channel with an internal diameter of 1.33 mm and 235 mm in heated length. A quartz tube with a homogeneous Indium Tin Oxide coating is used to allow heating and simultaneous visualization. Flow patterns have been observed along the heated length with the aid of high-speed complementary metal oxide semiconductor (CMOS) digital camera. From the flow boiling visualization, seven distinct two-phase flow patterns have been observed: isolated bubbly flow, confined bubbly flow, slug flow, churn flow, slug-annular flow, annular flow, and mist flow. Two-phase flow pattern observations are presented in the form of flow pattern maps. The effects of the saturation temperature and the inlet subcooling degree on the two-phase flow pattern transitions are elucidated. Finally, the experimental flow pattern map is compared with models developed for conventional sizes as well as to a microscale map for air-water mixtures available in literature, showing a large discrepancy.
Place, publisher, year, edition, pages
2010. Vol. 132, no 3, 031001- p.
boiling, flow visualisation, microchannel flow, pattern formation, refrigerants, two-phase flow, undercooling
Engineering and Technology
IdentifiersURN: urn:nbn:se:kth:diva-29077DOI: 10.1115/1.4000012ISI: 000273365100001ScopusID: 2-s2.0-77954538869OAI: oai:DiVA.org:kth-29077DiVA: diva2:391864
QC 201101252011-01-252011-01-252011-01-25Bibliographically approved