R134a vapour-liquid two-phase flow patterns were studied in vertical small-diameter tubes. The observed flow patterns include bubbly, dispersed bubble, slug, churn, annular, and mist flow. Six integrated flow pattern maps, derived for two internal diameters (2.01 and 4.26 mm) and three different pressures (6.0, 10.0, 14.0 bar), are presented. Some transition boundaries, such as slug-churn and churn-annular, were found to be very sensitive to diameter and pressure. In contrast the boundaries of dispersed bubble-churn and bubbly-slug are less affected. The transition boundaries are compared with the existing models for normal size tubes showing significant differences.
FukanoT.KariyasakiA.Characteristics of gas-liquid two-phase flow in a capillary tubeNuclear Engineering and Design, 1993, 141, 59–68.
2.
ZietlowD. C.PedersenC. O.Flow regime mapping and analysis of R-134a in a small-channel cross-flow condenserASHRAE Transactions, 1998, 104 (2), 540–547.
3.
WongwisesS.DisawasS.KaewonJ.OnuraiC.Two-phase evaporative heat transfer coefficients of refrigerant HFC-134a under forced flow conditions in a small horizontal tubeInt. Commun. Heat Mass Transfer, 2000, 27 (1), 35–48.
4.
OyaT.Upward liquid flow in small tube into which air streams (1st Report, Experimental apparatus and flow patterns), 1971, 14 (78), 1320–1329.
5.
BarneaD.LuninskiY.TaitelY.Flow pattern in horizontal and vertical two phase flow in small diameter pipesCan. J. Chem. Engng, 1983, 61 (5), 617–620.
6.
LinS.KewP. A.CornwellK.Two-phase flow regimes and heat transfer in small tubes and channels. In Proceedings of 11th IHTC, Heat Transfer1998, Vol. 2, August 23-28, Kyongju, Korea, 1998, pp. 45–50.
7.
KewP. A.CornwellK.Correlations for the prediction of boiling heat transfer in small-diameter channelsAppl. Therm. Engng, 1997, 17 (8-10), 705–715.
8.
BraunerN.Moalem-MaronD.Identification of the range of small diameter conduits, regarding two-phase flow pattern transitionsInt. Commun. Heat Mass Transfer, 1992, 19, 29–39.
MishimaK.HibikiT.Some characteristics of air-water two-phase flow in small diameter vertical tubesInt. J. Multiphase Flow, 1996, 22 (4), 703–712.
11.
DamianidesD. A.WestwaterJ. W.Two-phase flow patterns in a compact heat exchanger and in small tubes, In Second UK National Conference on Heat Transfer, Volume 11, Sessions 4A-6C, 1988, pp. 1257–1268.
12.
ColemanJ. W.GarimellaS.Characterization of two-phase flow patterns in small diameter round and rectangular tubesInt. J. Heat Mass Transfer, 1999, 42, 2869–2881.
13.
TaitelY.BarneaD.DuklerA. E.Modelling flow pattern transitions for steady upward gas-liquid flow in vertical tubesAIChE, 1980, 26, 345–354.
14.
MishimaK.IshiiM.Flow regime transition criteria for upward two-phase flow in vertical tubesInt. J. Heat Mass Transfer, 1984, 27 (5), 723–737.
15.
McQuilianK. W.WhalleyP. B.Flow patterns in vertical two-phase flowInt. J. Multiphase Flow, 1985, 11 (2), 161–175.
16.
TaitelY.Flow pattern transition in two phase flow. Keynote lecture, 9th International Heat Transfer Conference, Jerusalem, Israel, 19-24 August, pp. 237–254, 1990.
17.
TaitelY.DuklerA. E.A model for predicting flow regime transitions in horizontal and near-horizontal flowAIChE, 1996, 22, 47–55.
18.
SuoM.GriffithT.Two-phase flow in capillary tubesJ. Basic Engng, 1964, 86, 576–582.
19.
LinS.KewP. A.CornwellK.Characteristics of air/water flow in small tubesHeat and Technol., 1999, 17 (2), 63–70.
20.
ColemanH.W.SteeleW. G.Experimentation and Uncertainty Analysis for Engineers, 2nd Edition, 1999 (John Wiley & Sons, New York).
21.
BarneaD.An unified model for predicting flow-pattern transitions for the whole range of pipe inclinationsInt. J. Multiphase Flow, 1987, 13 (1), 1–12.
22.
BarneaD.BraunerN.Hold-up of the liquid slug in two phase intermittent flowInt. J. Multiphase Flow, 1985, 11 (1), 43–49.
