The thermal contact conductance (TCC) at the mechanically bonded tube/fin interface of a heat exchanger may be controlled by varying the amount of initial expansion of the tube. However, in this case, the TCC also varies with the temperature because of the differential expansion between the tube and the fin. The objectives of the present study are to determine the improvement in TCC resulting from higher degrees of the tube expansion, to determine the variation in TCC with the maximum temperature, and to estimate the change in contact pressure with the temperature. This paper presents the results of heat transfer experiments on mechanically expanded finned-tube specimens. Experiments were conducted in an atmosphere of nitrogen. The results showed that the TCC is enhanced by increasing the degree of initial expansion. There is a practical limit, however, to the maximum expansion that can be attempted. For the direction of heat flow prevailing in the experiments, the TCC and the contact pressure of every specimen decreased with increasing temperature.

1.
Madhusudana
,
C. V.
, 1996, “
Thermal Contact Conductance
,”
Mechanical Engineering Series
,
Springer-Verlag
, New York.
2.
Madhusudana
,
C. V.
, 2002, “
Recent Research in Contact Heat Transfer, 16th National Heat and Mass Transfer Conference & 5th ISHMT / ASME Heat and Mass Transfer Conference, India.
3.
Dart
,
D. M.
, 1959, “
Effect of Fin Bond on Heat Transfer
,”
ASHRAE J.
0001-2491,
1
, pp.
67
71
.
4.
Gardner
,
K. A.
, and
Carnavos
,
T. C.
, 1960, “
Thermal Contact Resistance in Finned Tubing. Transactions of ASME
,”
ASME Trans. J. Heat Transfer
0022-1481,
82
, pp.
279
293
.
5.
Eckels
,
P. W.
, 1977, “
Contact Conductance of Mechanically Expanded Plate Finned Tube Heat Exchangers
,” ASME Paper, August, pp.
15
17
.
6.
Sheffield
,
J. W.
,
Sauer
,
H. J.
, and
Wood
,
R. A.
, 1987, “
An Experimental Method for Measuring the Thermal Contact Resistance of Plate Finned Tube Heat Exchangers
,”
ASHRAE J.
0001-2491,
93
, pp.
776
785
.
7.
Nho
,
K. M.
, and
Yovanovich
,
M. M.
, 1989, “
Measurement of Contact Resistance in Finned Tube Heat Exchangers
,”
ASHRAE J.
0001-2491
95
(
1
), pp.
370
378
.
8.
Critoph
,
R. E.
,
Holland
,
M. K.
, and
Turner
,
L.
, 1996, “
Contact Resistance in Air-Cooled Plate Fin-Tube Air-conditioning Condensers
,”
Int. J. Refrig.
0140-7007,
9
, pp.
400
406
.
9.
ElSherbini
,
A. I.
,
Jacobi
,
A. M.
, and
Hrnjak
,
P. S.
, 2003, “
Experimental investigation of Thermal Contact Resistance in Plain-Fin and Tube Evaporators With Collarless Fins
,”
Int. J. Refrig.
0140-7007,
26
, pp.
527
536
.
10.
Kim
,
C. N.
,
Jeong
,
J.
, and
Youn
,
B.
, 2003, “
Evaluation of Thermal Contact Conductance Using a New Experimental-Numerical Method in Fin-Tube Heat Exchangers
,”
Int. J. Refrig.
0140-7007,
26
, pp.
900
908
.
11.
Jeong
,
J.
,
Kim
,
C. N.
,
Youn
,
B.
, and
Kim
,
Y. S.
, 2004, “
A Study on the Correlation Between the Thermal Contact Conductance and Effective Factors in Fin-Tube Heat Exchangers With 9.52mm Tube
,”
Int. J. Heat Fluid Flow
0142-727X,
25
, pp.
1006
1014
.
12.
Madhusudana
,
C. V.
,
Fletcher
,
L. S.
, and
Peterson
,
G. P.
, 1990, “
Thermal Conductance of Cylindrical Joints—A Critical Review
,”
J. Thermophys. Heat Transfer
0887-8722,
4
, pp.
204
211
.
13.
Wahid
,
S. M. S.
, and
Madhusudana
,
C. V.
, 2000, “
Gap Conductance in Contact Heat Transfer
,”
Int. J. Heat Mass Transfer
0017-9310,
43
, pp.
4483
4487
.
14.
Mikic
,
B. B.
, 1974, “
Thermal Contact Conductance: Theoretical Considerations
,”
Int. J. Heat Mass Transfer
0017-9310,
17
, pp.
205
214
.
15.
Tien
,
C. L.
, 1968, “
A Correlation for Thermal Contact Conductance of Nominally Flat Surfaces in Vacuum
,”
Proceedings of the 7th Conference on Thermal Conductivity
,
U.S. National Bureau of Standards
, Gaithersburg, pp.
311
320
.
16.
Cheng
,
W. W.
, and
Madhusudana
,
C. V.
, 2004, “
Design and Fabrication of a Test Apparatus for Measuring Thermal Contact Conductance in a Finned-Tube Heat Exchanger
,”
17th National Heat and Mass Transfer Conference & 6th ISHMT/ASME Heat and Mass Transfer Conference
, India.
17.
Cengel
,
Y. A.
, 1998,
Heat Transfer a Practical Approach
,
WCB/McGraw-Hill
, New York, p.
963
.
18.
Holman
,
J. P.
, 1971,
Experimental Methods for Engineers
,
2nd ed.
,
McGraw-Hill
, New York, pp.
37
44
.
You do not currently have access to this content.