A semiempirical model is proposed to predict the condensation coefficient inside small hydraulic diameter extruded aluminum tubes having microgrooves. The model accounts for the effects of vapor shear and surface tension forces. Surface tension force is effective in enhancing the condensation coefficient as long as the fin tips are not flooded by condensate. This enhancement increases as mass velocity is reduced. At high mass velocity the flow is vapor shear controlled and the surface tension contribution is very small. The surface tension effect is strongly affected by the fin geometry. A smaller fin tip radius provides a higher surface tension drainage force. A large cross sectional area in the interfin region will allow the surface tension enhancement to occur at lower vapor quality. Separate models are developed for the surface tension and vapor shear controlled regimes and the models are combined in the form of an asymptotic equation. The vapor shear model is based on use of an equivalent mass velocity and the heat-momentum transfer analogy. The surface tension model is analytically based. The model is validated by predicting the authors data for two tube geometries using R-12 and R-134a, and the model predicts 95 percent of the condensation data within ±16 percent.

Issue Section:
Boiling and Condensation
Keywords:
Augmentation and Enhancement, Condensation, Heat Exchangers
Topics:
Condensation, Fins
1.
Akers
W. W.
,
Deans
H. A.
, and
Crosser
O. K.
,
1959
, “
Condensation Heat Transfer Within Horizontal Tubes
,”
Chem. Eng. Prog. Symp. Ser.
, Vol.
55
, No.
29
, pp.
171
–
176
.
2.
Carpenter, F. G., and Colburn, A. P., 1951, “The Effect of Vapor Velocity on Condensation Inside Tubes,” Proceedings of the General Discussion of Heat Transfer, The Institute of Mechanical Engineers and the ASME, pp. 20–26.
3.
Cavallini, A., and Zecchin, R., 1974, “A Dimensionless Correlation for Heat Transfer in Forced Convection Condensation,” Proceedings of the Fifth International Heat Transfer Conference, Vol. 3, ASME, NY, pp. 309–313.
4.
Gregorig
R.
,
1954
, “
Film Condensation on Finely Rippled Surface with Condensation of Surface Tension
,”
Zeitschrift fur Angewandte Mathematik und Physik
, Vol.
V
, pp.
36
–
49
, (quoted in Webb (1994)).
5.
Khanpara, J. C., Bergles, A. E., and Pate, M. B., 1986, “Augmentation of R-113 In-Tube Condensation with Micro-Fin Tubes,” Heat Transfer in Air Conditioning and Refrigeration Equipment, ASME, NY.
6.
Morita, H., Kito, Y., and Satoh, Y., 1993, “Recent Improvements in Small Bore Inner Grooved Copper Tube,” Tube & Pipe Technology, November/December, pp. 53–57.
7.
Seider
E. N.
, and
Tate
C. E.
,
1936
, “
Heat Transfer and Pressure Drop of Liquids in Tubes
,”
Ind. Eng. Chem.
, Vol.
28
, p.
1429
1429
.
8.
Shah
M. M.
,
1979
, “
A General Correlation for Heat Transfer During Film Condensation in Tubes
,”
Int. Jour. of Heat and Mass Transfer
, Vol.
22
, No.
4
, pp.
547
–
556
.
9.
Tsuchida, T., 1993, “Internal Heat Transfer Characteristics and Workability of Narrow THERMOFIN Tubes,” Hitachi Cable Review, No. 12, pp. 59–64.
10.
Webb, R. L., 1994, chap. 14 in Principles of Enhanced Heat Transfer, Wiley Interscience.
11.
Webb, R. L., and Yang, C.-Y., 1995, “Condensation of R-12 and R-134a in Brazed Aluminum Automotive Heat Exchangers,” 1995 Vehicle Thermal Management Systems, Society of Automotive Engineers, Warrendale, PA, pp. 77–85.
12.
Yang, C.-Y., 1994, “A Theoretical and Experimental Study of Condensation in Flat Extruded Micro-fin Tubes,” Ph.D. thesis, The Pennsylvania State University, PA.
13.
Yang
C.-Y.
, and
Webb
R. L.
,
1996
a, “
Condensation of R-12 in Small Hydraulic Diameter Extruded Aluminum Tubes With and Without Micro-fins
,”
Int. Jour. of Heat and Mass Transfer
, Vol.
39
, No.
4
, pp.
791
–
800
.
14.
Yang
C.-Y.
, and
Webb
R. L.
,
1996
b, “
Friction Pressure Drop of R-12 in Small Hydraulic Diameter Extruded Aluminum Tubes With and Without Micro-fins
,”
Int. Jour. Heat and Mass Transfer
, Vol.
39
, No
4
, pp.
801
–
809
.
15.
Zivi
S. M.
,
1964
, “
Estimation of Steady State Steam Void-Fraction by Means of Principle of Minimum Entropy Production
,”
ASME JOURNAL OF HEAT TRANSFER
, Vol.
86
, pp.
237
–
252
.
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