Limited previous work has shown that use of special hydrophilic coatings will provide lower air pressure drop in finned tube heat exchangers operated under dehumidifying conditions. However, no detailed work has been reported on the effect of different coating types, or different fin surface geometries on the wet pressure drop. In this study, wind tunnel tests were performed on three different fin geometries (wavy, lanced, and louver) under wet and dry conditions. All dehumidification tests were done for fully wet surface conditions. For each geometry, the tests were performed on uncoated and coated heat exchangers. For all three fin geometries, the wet-to-dry pressure drop ratio was 1.2 at 2.5 m/s frontal air velocity. The coatings have no influence on the wet or dry heat transfer coefficient. However, the wet surface heat transfer coefficient was 10 to 30 percent less than the dry heat transfer coefficient, depending on the particular fin geometry. The effect of the fin press oil on wet pressure drop was also studied. If the oil contains a surfactant, good temporary wetting can be obtained on an uncoated surface; however, this effect is quickly degraded as the oil is washed from the surface during wet operation. This work also provides a critical assessment of data reduction methods for wet surface operation, including calculation of the fin efficiency.

1.
Brognaux
L. J.
,
Webb
R. L.
,
Chamra
L. M.
, and
Chung
B. K.
,
1997
, “
Single-Phase Heat Transfer in Micro-Fin Tubes
,”
Int. Journal of Heat and Mass Transfer
, Vol.
40
, pp.
4345
4358
.
2.
Charters
W. W. S.
, and
Theerakulpisut
S.
,
1989
, “
Efficiency Equations for Constant Thickness Annular Fins
,”
Int. Comm. Heat Mass Transfer
, Vol.
16
, pp.
547
558
.
3.
Eckels
P. W.
, and
Rabas
T. J.
,
1987
, “
Dehumidification: On the Correlation of Wet and Dry Transport Processes in Plate Finned-Tube Heat Exchangers
,”
ASME JOURNAL OF HEAT TRANSFER
, Vol.
109
, pp.
574
582
.
4.
Holman, J. P., 1989, Heat Transfer, 7th Ed., McGraw-Hill, New York.
5.
Hong, K., 1996, “Fundamental Characteristics of the Dehumidifying Heat Exchangers With and Without the Wetting Coatings,” Ph.D. thesis, The Pennsylvania State University, University Park, PA.
6.
Hong
K.
, and
Webb
R. L.
,
1996
., “
Calculation of Fin Efficiency for Wet and Dry Fins
,”
Int. J. HVAC & R Research
, Vol.
2
, No.
1
, pp.
27
41
.
7.
Hong, K. T., and Webb, R. L., 1999, “Wetting Coating Characteristics of Dehumidifying Heat Exchangers,” Int. Journal of HVAC&R, in press.
8.
Kays, W. M., and London, A. L., 1984, Compact Heat Exchangers, McGraw-Hill, New York.
9.
Kim, G. R., and Webb, R. L., 1996, “Hydrophilic Treatment for Dehumidifying Heat Exchanger,” technical report to LG Electronics.
10.
Kline, S. J., 1965, Similitude and Approximation Theory, McGraw-Hill, New York.
11.
McQuiston, F. C., and Parker, J. D., 1994, Heating, Ventilating, and Air Conditioning, John Wiley and Sons, New York.
12.
McQuiston
F. C.
,
1975
, “
Fin Efficiency with Combined Heat and Mass Transfer
,”
ASHRAE Transactions
, Vol.
81
, Part 1, pp.
350
355
.
13.
McQuiston
F. C.
,
1978
a, “
Heat, Mass and Momentum Transfer Data For Five Plate-Fin-Tube Heat Transfer Surfaces
,”
ASHRAE Transactions
, Vol.
84
, Part 1, pp.
266
293
.
14.
Mimaki
M.
,
1987
, “
Effectiveness of Finned-Tube Heat Exchanger Coated Hydrophilic-Type Film
,”
ASHRAE Transactions
, Vol.
93
, Part 1, pp.
62
71
.
15.
Petukhov, B. S., 1970, Advances in Heat Transfer, Vol. 6, T. F. Irvine and J. P. Hartnett, eds., Academic Press, New York, 1970.
16.
Schmidt, T. E., 1945-1946, “La Production Calorifique des Surfaces Munies D’ailettes,” Annexe Du Bulletin De L’institut International Du Froid, Annexe G-5.
17.
Threlkeld, J. L., 1970, Thermal Environmental Engineering, Prentice-Hall, Engle-wood Cliffs, NJ.
18.
Wu
G.
, and
Bong
T. Y.
,
1994
, “
Overall Efficiency of a Straight Fin with Combined Heat and Mass Transfer
,”
ASHRAE Transactions
, Vol.
100
, No.
1
, pp.
367
374
.
This content is only available via PDF.
You do not currently have access to this content.