Adiabatic gas-liquid two-phase flow patterns and void fractions in micro-channels were experimentally investigated. Using nitrogen gas and water, experiments were conducted in near-square micro-channels with hydraulic diameters of 0.209mm, 0.412mm and 0.622 mm, respectively. The main objective was focused on the effects of micro-scale channel sizes. Gas and liquid superficial velocities were varied from 0.06-72.3 m/s and 0.02-7.13 m/s, respectively. Four defined flow patterns including bubbly-slug flow, slug-ring flow, dispersed-churn flow and annular flow were observed in both micro-channels of 0.412 mm and, 0.622 mm in hydraulic diameter. In the micro-channel of 0.209 mm, the bubbly-slug flow turned into the slug-flow and the dispersed-churn flow was not observed. The current flow regime maps showed that the transition lines shifted towards higher gas superficial velocity due to the stronger surface tension effect as the channel size was reduced. The micro-channel flow regime maps were found to be quite different from those of mini-channels. Measured time-averaged void fractions in our micro-channels held a non-linear relationship with the homogeneous void fraction as oppose to the relatively linear trend for the mini-channels. A new correlation was proposed to predict the non-linear relationship that fits most of the experimental data of the current three micro-channels and those of the 0.1 mm diameter tube reported by Kawahara et al. within ± 15%.

1.
Mandhane
J. M.
,
Gregory
G. A.
,
Aziz
K.
,
1974
, “
Flow pattern map for gas-liquid flow in horizontal pipes
,”
Int. J. Multiphase Flow
,
1
, pp.
537
537
.
2.
Taitel
Y.
,
Dukler
A. E.
,
1976
, “
A model for predicting flow regime transitions in horizontal and near horizontal gas-liquid flow
,”
AIChE J.
,
22
, pp.
47
47
.
3.
Triplett
K. A.
,
Ghiaasiaan
S. M.
,
Abdel-Khalik
S. I.
,
Sadowski
D. L.
,
1999
, “
Gas-liquid two-phase flow in micro-channels Part I: two-phase flow patterns
,”
Int. J. Multiphase Flow
,
25
, pp.
377
377
.
4.
Chen
W. L.
,
Twu
M. C.
,
Pan
C.
,
2002
, “
Gas-liquid two-phase flow in micro-channels
,”
Int. J. Multiphase Flow
,
28
, pp.
1235
1235
.
5.
Kawahara
A.
,
Chung
P. M. Y.
,
Kawaji
M.
,
2002
, “
Investigation of two-phase flow pattern, void fraction and pressure drop in a microchannel
,”
Int. J. Multiphase Flow
,
28
, pp.
1411
1411
.
6.
Qu
W.
,
Yoon
S. M.
,
Mudawar
I.
,
2004
, “
Two-phase flow and heat transfer in rectangular micro-channels
,”
J. Electronic Packaging
,
126
, pp.
288
288
.
7.
Zuber
N.
,
Findlay
J. A.
,
1965
, “
Average volumetric concentration in two-phase flow systems
,”
ASME J. Heat Transfer
,
87
, pp.
453
453
.
8.
Mishima
K.
,
Hibiki
T.
,
Nishihara
H.
,
1991
, “
Some characteristics of gas-liquid flow in narrow rectangular ducts
,”
Proc. of Int. Conf. on Multiphse Flows
,
2
, pp.
485
485
.
9.
Ali
M. I.
,
Sadatomi
M.
,
Kawaji
M.
,
1993
, “
Two-phase flow in narrow channels between two flat plates
,”
Can. J. Chem. Eng.
,
71
, pp.
657
657
.
10.
Chung
P. M. Y.
,
Kawaji
M.
,
Kawahara
A.
,
Shibata
Y.
,
2004
, “
Investigation of two-phase flow pattern, void fraction and pressure drop in a microchannel
,”
J. Fluids Eng.-Trans. ASME
,
126
, pp.
546
546
.
11.
Serizawa
A.
,
Feng
Z. P.
,
Kawara
Z.
,
2002
, “
Two-phase flow in microchannels
,”
Exp. Therm Fluid Sci.
,
26
, pp.
703
703
.
12.
Taitel
T.
,
Barnea
D.
,
Dukler
A. E.
,
1980
, “
Modeling flow pattern transitions for steady upward gas-liquid flow in vertical tubes
,”
AIChE J.
,
26
, pp.
345
345
.
13.
Mishima
K.
,
Ishii
M.
,
1984
, “
Flow regime transition criteria for upward two-phase flow in vertical tubes
,”
Int. J. Heat Mass Transfer
,
27
, pp.
723
723
.
14.
Tabatabai
A.
,
Faghri
A.
,
2001
, “
A new two-phase flow map and transition boundary accounting for surface tension effects in horizontal miniature and micro tubes
,”
J. Fluids Eng.-Trans. ASME
,
123
, pp.
958
958
.
15.
Akbar
M. K.
,
Plummer
D. A.
,
Ghiaasiaan
S. M.
,
2003
, “
On gas-liquid two-phase flow regimes in microchannels
,”
Int. J. Multiphase Flow
,
29
, pp.
855
855
.
16.
Damianides, C.A., Westwater, J.W., 1988, “Two-phase flow in a compact heat exchanger and in small tubes,” In: Proc. Second UK National Conf. On Heat Transfer, pp.1257.
17.
Yang
C. Y.
,
Shieh
C. C.
,
2001
, “
Flow pattern of air-water and two-phase R-134a in small circular tubes
,”
Int. J. Multiphase Flow
,
27
, pp.
1163
1163
.
This content is only available via PDF.
You do not currently have access to this content.