A stratified flow model of film condensation in helically grooved, horizontal microfin tubes has been developed. The height of stratified condensate was estimated by extending the Taitel and Dukler model for a smooth tube to a microfin tube. For the upper part of the tube exposed to the vapor flow, laminar film condensation due to the combined effects of gravity and surface tension forces was assumed. For the lower part of the tube exposed to the stratified condensate flow, the heat transfer coefficient was estimated by an empirical equation for the internally finned tubes developed by Carnavos. The theoretical predictions of the circumferential average heat transfer coefficient by the present model and previously proposed annular flow model were compared with available experimental data for five tubes and five refrigerants. It was shown that the stratified flow model was applicable to wide ranges of mass velocity and quality as long as the vapor to liquid density ratio was larger than 0.05. Comparison was also made with the predictions of previously proposed empirical equations.

Issue Section:
Evaporation, Boiling, and Condensation
Keywords:
pipe flow, heat exchangers, film condensation, stratified flow, laminar flow, two-phase flow, Condensation, Enhancement, Heat Transfer, Modeling, Two-Phase
Topics:
Condensed matter, Film condensation, Heat transfer coefficients, Stratified flow, Vapors, Flow (Dynamics), Surface tension
1.
Webb, R. L., 1994, Principles of Enhanced Heat Transfer, chap. 14, John Wiley and Sons, New York.
2.
Newell, T. A., and Shah, R. K., 1999, “Refrigerant Heat Transfer, Pressure Drop, and Void Fraction Effects in Microfin Tubes,” Proceedings of 2nd International Symposium on Two-Phase Flow and Experimentation, Pisa, Italy, Vol. 3, pp. 1623–1639.
3.
Cavallini, A., Doretti, L., Klammsteiner, N., Longo, G. A., and Rosetto, L., 1995, “Condensation of New Refrigerants Inside Smooth and Enhanced Tubes,” Proceedings of 19th International Congress of Refrigeration, Vol. IV, pp. 105–114.
4.
Cavallini
,
A.
,
Del Col
,
D.
,
Doretti
,
L.
,
Longo
,
G. A.
, and
Rosetto
,
L.
,
1999
, “
A New Computational Procedure for Heat Transfer and Pressure Drop during Refrigerant Condensation Inside Enhanced Tubes
,”
Journal of Enhanced Heat Transfer
,
6
, No.
1
, pp.
441
–
456
.
5.
Shikazono
,
N.
,
Itoh
,
M.
,
Uchida
,
M.
,
Fukushima
,
T.
, and
Hatada
,
T.
,
1998
, “
Predictive Equation Proposal for Condensation Heat Transfer Coefficient of Pure Refrigerants in Horizontal Microfin Tubes
,”
Transactions of JSME
,
64
, pp.
196
–
203
.
6.
Kedzierski
,
M. A.
, and
Goncalves
,
J. M.
,
1999
, “
Horizontal Convective Condensation of Alternative Refrigerants Within a Micro-Fin Tube
,”
Journal of Enhanced Heat Transfer
,
6
, No.
2–4
, pp.
161
–
178
.
7.
Yang
,
C. Y.
, and
Webb
,
R. L.
,
1997
, “
A Predictive Model for Condensation in Small Hydraulic Diameter Tubes Having Axial Microfins
,”
ASME J. Heat Transfer
,
119
, No.
4
, pp.
776
–
782
.
8.
Nozu
,
S.
, and
Honda
,
H.
,
2000
, “
Condensation of Refrigerants in Horizontal, Spirally Grooved Microfin Tubes: Numerical Analysis of Heat Transfer in Annular Flow Regime
,”
ASME J. Heat Transfer
,
122
, No.
1
, pp.
80
–
91
.
9.
Taitel
,
Y.
, and
Dukler
,
A. E.
,
1976
, “
A Model for Predicting Flow Regime Transitions in Horizontal and Near Horizontal Gas-Liquid Flow
,”
AIChE J.
,
22
, No.
1
, pp.
47
–
55
.
10.
Carnavos
,
T. C.
,
1980
, “
Heat Transfer Performance of Internally Finned Tubes in Turbulent Flow
,”
Heat Transfer Eng.
,
4
, No.
1
, pp.
32
–
37
.
11.
Haraguchi, H., 1994, “Studies on Condensation of HCFC-22, HFC-134a and HCFC-123 in Horizontal Tubes,” Dr. Eng. thesis, Kyushu University.
12.
Hayashi, T., 1998, “Enhancement of Condensation of HFC-134a in Horizontal Tubes,” M. Eng. thesis, Kyushu University.
13.
Miyara
,
A.
,
Nonaka
,
K.
, and
Taniguchi
,
M.
,
2000
, “
Condensation Heat Transfer and Flow Pattern Inside a Herringbone-Type Microfin Tube
,”
Int. J. Refrig.
,
23
, No.
1
, pp.
141
–
152
; also private communication.
14.
Mclinden, M. O., Klein, S. A., Lemmon, E. W., and Peskin, A. P., 1998, NIST Thermodynamic and Transport Properties of Refrigerants and Refrigerant Mixtures—REFPROP, Version 6.0.
15.
Luu
,
M.
, and
Bergle
,
A. E.
,
1980
, “
Enhancement of Horizontal In-Tube Condensation of Refrigerant-113
,”
ASHRAE Trans.
,
86
, Pt. 1, pp.
293
–
312
.
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