It is well known that heat transfer in dropwise condensation (DWC) is superior to that in filmwise condensation (FWC) by at least one order of magnitude. Surfaces with larger contact angle (CA) can promote DWC heat transfer due to the formation of “bare” condensation surface caused by the rapid removal of large condensate droplets and high surface replenishment frequency. Superhydrophobic surfaces with high contact angle (> 150°) of water and low contact angle hysteresis (< 5°) seem to be an ideal condensing surface to promote DWC and enhance heat transfer, in particular, for the steam-air mixture vapor. In the present paper, steam DWC heat transfer characteristics in the presence of noncondensable gas (NCG) were investigated experimentally on superhydrophobic and hydrophobic surfaces including the wetting mode evolution on the roughness-induced superhydrophobic surface. It was found that with increasing NCG concentration, the droplet conducts a transition from the Wenzel to Cassie-Baxter mode. And a new condensate wetting mode—a condensate sinkage mode—was observed, which can help to explain the effect of NCG on the condensation heat transfer performance of steam-air mixture on a roughness-induced superhydrophobic SAM-1 surface.

References

References
1.
Schmidt
,
E.
,
Schurig
,
W.
, and
Sellschopp
,
W.
, 1930, “
Versuche über die Kondensation von Wasserdampf in Film-und Tropfenform
,”
Forsch. Ingenieurwes.
,
1
(
2
), pp.
53
63
.
2.
Rose
J. W.
, 2002, “
Dropwise Condensation Theory and Experiment: A Review
,”
Proc. IME J. Power Energy
,
216
, pp.
115
128
.
3.
Lan
,
Z.
,
Ma
,
X. H.
,
Zhou
,
X. D.
, and
Wang
,
M. Z.
, 2009, “
Theoretical Study of Dropwise Condensation Heat Transfer: Effect of the Liquid-Solid Surface Free Energy Difference
,”
J. Enhanced Heat Transfer
,
16
, pp.
61
71
.
4.
Kim
,
S.
, and
Kim
,
K. J.
, 2011, “
Dropwise Condensation Modeling Suitable for Superhydrophobic Surfaces
,”
ASME Trans., J. Heat Transfer
,
133
, pp.
081502
.
5.
Sikarwar
,
B. S.
,
Battoo
,
N. K.
,
Khandekar
,
S.
, and
Muralidhar
,
K.
, 2011, “
Dropwise Condensation Underneath Chemically Textured Surfaces: Simulation and Experiments
,”
ASME Trans., J. Heat Transfer
,
133
, pp.
021501
.
6.
Gao
,
L. C.
, and
McCarthy
,
T. J.
, 2006, “
The ‘Lotus Effect’ Explained: Two Reasons Why Two Length Scales of Topography Are Important
,”
Langmuir
,
22
, pp.
2966
2967
.
7.
Wenzel
,
R. N.
, 1936, “
Resistance of Solid Surfaces to Wetting by Water
,”
Ind. Eng. Chem.
,
28
, pp.
988
994
.
8.
Cassie
,
A. B. D.
, and
Baxter
S.
, 1944, “
Wettability of Porous Surfaces
,”
Trans. Faraday Soc.
,
40
, pp.
546
551
.
9.
Marmur
,
A.
, 2003, “
Wetting on Hydrophobic Rough Surfaces: To be Heterogeneous or Not to Be?
,”
Langmuir
,
19
, pp.
8343
8348
.
10.
Patankar
,
N. A.
, 2003, “
On the Modeling of Hydrophobic Contact Angles on Rough Surfaces
,”
Langmuir
,
19
, pp.
1249
1253
.
11.
Wier
,
K. A.
, and
McCarthy
,
T. J.
, 2006, “
Condensation on Ultrahydrophobic Surfaces and Its Effect on Droplet Mobility: Ultrahydrophobic Surfaces Are Not Always Water Repellant
,”
Langmuir
,
22
, pp.
2433
2436
.
12.
Herminghaus
,
S.
, 2000, “
Roughness-Induced Non-Wetting
,”
Europhys. Lett.
,
52
, pp.
165
170
.
13.
Miljkovic
,
N.
,
Enright
,
R.
,
Maroo
,
S. C.
,
Cho
,
H. J
, and
Wang
,
E. N.
, 2011, “
Liquid Evaporation on Superhydrophobic and Superhydrophilic Nanostructured Surfaces
,”
ASME Trans., J. Heat Transfer
,
133
, pp.
080903
.
14.
Kim
,
T. J.
,
Glass
,
P.
, and
Hidrovo
,
C. H.
, 2011, “
Thermo-Wetting and Friction Reduction Characterization of Microtextured Superhydrophobic Surfaces
,”
ASME Conf. Proc.
,
38921
, pp.
T30055
–T30055-
6
.
15.
Ng
,
C. O.
, and
Wang
,
C. Y.
, 2011, “
Oscillatory Flow Through a Channel With Stick-Slip Walls: Complex Navier’s Slip Length
,”
J. Fluids Eng.
,
133
, pp.
014502
.
16.
Cheng
,
Y. T.
,
Rodak
,
D. E.
,
Angelopoulos
,
A.
, and
Gacek
,
T.
, 2005, “
Microscopic Observations of Condensation of Water on Lotus Leaves
,”
Appl. Phys. Lett.
,
87
, pp.
194112
194113
.
17.
Narhe
,
R. D.
, and
Beysens
,
D. A.
, 2007, “
Growth Dynamics of Water Drops on a Square-Pattern Rough Hydrophobic Surface
,”
Langmuir
,
23
, pp.
6486
6489
.
18.
Yung
,
C. C.
, and
Bushan
,
B.
, 2008, “
Wetting Behavior During Evaporation and Condensation of Water Microdroplets on Superhydrophobic Patterned Surfaces
,”
J. Microsc.
,
229
, pp.
127
140
.
19.
Dorrer
,
C.
, and
Rühe
,
J.
, 2009, “
Some Thoughts on Superhydrophobic Wetting
,”
Soft Matter
,
5
, pp.
51
61
.
20.
Lau
,
K. K. S.
,
Bico
,
J.
,
Teo
,
K. B. K.
,
Chhowalla
,
M.
,
Amaratunga
,
G. A. J.
,
Milne
,
W. I.
,
McKinley
,
G. H.
, and
Gleason
,
K. K.
, 2003, “
Superhydrophobic Carbon Nanotube Forests
,”
Nano Lett.
,
3
, pp.
1701
1705
.
21.
Chen
,
C.-H.
,
Cai
,
Q.
, and
Chen
,
C.-L.
, 2008, “
Evaporation and Condensation on Two-Tier Superhydrophobic Surfaces
,”
ASME Conf. Proc.
,
42924
, pp.
1021
1022
.
22.
Boreyko
,
J. B.
, and
Chen
,
C.-H.
, 2009, “
Self-Propelled Dropwise Condensate on Superhydrophobic Surfaces
,”
Phys. Rev. Lett.
,
103
(
18
), pp.
184501
.
23.
Lan
,
Z.
,
Ma
,
X. H.
,
Wang
,
S. F.
,
Wang
,
M. Z.
, and
Li
,
X. N.
, 2010, “
Effect of Surface Free Energy and Nanostructures on Dropwise Condensation
,”
Chem. Eng. J.
,
156
, pp.
546
552
.
24.
Kim
,
M. H.
, and
Kang
,
H. C.
, 1993, “
Condensation Phenomena With Wavy Interface in the Presence of a Noncondensable Gas
,”
Proceedings of the Engineering Foundation Conference on Condensation and Condenser Design, St. Augustine, Florida
,
ASME
, pp.
219
230
.
25.
Park
,
S. K.
,
Kim
,
M. H.
, and
Yoo
,
K. J.
, 1996, “
Condensation of Pure Steam and Steam-Air Mixture With Surface Waves of Condensate Film on a Vertical Wall
,”
Int. J. Multiphase Flow
,
22
, pp.
893
908
.
26.
Sundararaman
,
T. G.
, and
Venkatram
,
T.
, 1976, “
Heat Transfer During DWC of Steam in the Presence of Non-Condensable Gases Effects of Geometrical Shape of the Surface Reversal of Cooling of Water Flow and Orientation
,”
Ind. J. Technol.
,
14
, pp.
313
321
.
27.
Abdulhadi
,
M.
, 1987, “
Estimation of Air Traces in Steam-Air Mixtures Subjected to Dropwise Condensation
,”
Int. Commun. Heat Mass Transfer
,
14
, pp.
347
351
.
28.
Jackson
,
J. D.
,
An
,
P.
, and
Ahmadinejad
,
M.
, 2002, “
Effects of Non-Condensable Gas on the Condensation of Steam
,”
Proceedings of 12th International Heat Transfer Conference, Heat Transfer 2002
,
3
, pp.
911
916
.
29.
Ma
,
X. H.
,
Zhou
,
X. D.
,
Lan
,
Z.
,
Li
,
Y. M.
, and
Zhang
,
Y.
, 2008, “
Condensation Heat Transfer Enhancement in the Presence of Non-Condensable Gas Using the Interfacial Effect of Dropwise Condensation
,”
Int. J. Heat Mass Transfer
,
51
, pp.
1728
1737
.
30.
Ma
,
X. H.
,
Zhou
,
X. D.
,
Lan
,
Z.
,
Song
,
T. Y.
, and
Ji
,
J.
, 2007, “
Experimental Investigation of Enhancement of Dropwise Condensation Heat Transfer of Steam-Air Mixture: Falling Droplet Effect
,”
J. Enhanced Heat Transfer
,
14
, pp.
295
305
.
31.
Kline
,
S. J.
, and
McClintock
,
F. A.
, 1953, “
Describing Uncertainties in Single-Sample Experiments
,”
Mech. Eng.
,
75
, pp.
3
8
.
32.
Ma
,
X. H.
,
Wang
,
S. F.
,
Lan
,
Z.
,
Wang
,
A. L.
, and
Peng
,
B. L.
, 2010, “
Dropwise Condensation Heat Transfer on Superhydrophobic Surface in the Presence of Non-Condensable Gas
,”
ASME Conf. Proc.
,
49378
, pp.
71
79
.
33.
Bormashenko
,
E.
,
Pogreb
,
R.
,
W.
Gene.
, and
Erlich
,
M.
, 2007, “
Resonance Cassie-Wenzel Wetting Transition for Horizontally Vibrated Drops Deposited on a Rough Surface
,”
Langmuir
,
23
, pp.
12217
12221
.
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