This paper presents the results of an experimental study of forced convection heat transfer in a narrow rectangular duct fitted with an elliptical tube and one or two delta-winglet pairs. The duct was designed to simulate a single passage in a fin-tube heat exchanger. Heat transfer measurements were obtained using a transient technique in which a heated airflow is suddenly introduced to the test section. High-resolution local fin-surface temperature distributions were obtained at several times after initiation of the transient using an imaging infrared camera. Corresponding local fin-surface heat transfer coefficients were then calculated from a locally applied one-dimensional semi-infinite inverse heat conduction model. Heat transfer results were obtained over a Reynolds number range based on duct height of 670–6300. Pressure-drop measurements have also been obtained for similar elliptical-tube and winglet geometries, using a separate single-channel, multiple-tube-row pressure-drop apparatus. The pressure-drop apparatus includes four tube rows in a staggered array. Comparisons of heat transfer and pressure-drop results for the elliptical tube versus a circular tube with and without winglets are provided. Mean heat transfer results indicated that the addition of the single winglet pair to the oval-tube geometry yielded significant heat transfer enhancement, averaging 38% higher than the oval-tube, no-winglet case. The corresponding increase in friction factor associated with the addition of the single winglet pair to the oval-tube geometry was very modest, less than 10% at ReDh=500 and less than 5% at ReDh=5000.

Issue Section:
Heat Exchangers
Keywords:
heat exchangers, pipe flow, forced convection, temperature distribution, infrared imaging, heat conduction, friction, vortices, flow visualisation
Topics:
Flow (Dynamics), Heat exchangers, Heat transfer, Pressure drop, Vortices, Reynolds number, Heat transfer coefficients, Friction, Ducts, Generators
1.
O’Brien, J. E., and Sohal, M. S., 2000, “Local Heat Transfer for Finned-Tube Heat Exchangers Using Oval Tubes,” Proc. of 2000 ASME National Heat Transfer Conference, Pittsburgh, Paper No. NHTC2000-12093, CD-ROM, ASME, New York.
2.
O’Brien, J. E., and Sohal, M. S., 2000, “Heat Transfer Enhancement for Finned-tube Heat Exchangers with Winglets,” Proc. of 2000 ASME Int. Congress and Exposition, Orlando, HTD-Vol. 365/PID-Vol. 4, ASME, New York, pp. 137–146.
3.
Foust, T. D., O’Brien, J. E., and Sohal, M. S., 2001, “Numerical and Experimental Methods for Heat Transfer Enhancement for Finned-Tube Heat Exchangers with Oval Tubes,” 2001 ASME National Heat Transfer Conference, Anaheim, Paper No. NHTC01-12363.
4.
Jacobi
,
A. M.
, and
Shah
,
R. K.
,
1995
, “
Heat Transfer Surface Enhancement Through the Use of Longitudinal Vortices: A Review of Recent Progress
,”
Exp. Therm. Fluid Sci.
,
11
, pp.
295
–
309
.
5.
Fiebig, M., Kallweit, P., and Mitra, N. K., 1986, “Wing Type Vortex Generators for Heat Transfer Enhancement,” Heat Transfer 1986, Proc. of 8 Int. Heat Transfer Conf., Hemisphere, New York, Vol. 6, pp. 2903–2908.
6.
Fiebig
,
M.
,
Valencia
,
A.
, and
Mitra
,
N. K.
,
1994
, “
Local Heat Transfer and Flow Losses in Fin-Tube Heat Exchanger with Vortex Generators: A Comparison of Round and Flat Tubes
,”
Exp. Therm. Fluid Sci.
,
8
(
1
), pp.
35
–
45
.
7.
Wang
,
L. B.
,
Ke
,
F.
,
Gao
,
S. D.
, and
Mei
,
Y. G.
,
2002
, “
Local and Average Characteristics of Heat/Mass Transfer Over Flat Tube Bank Fin With Four Vortex Generators per Tube
,”
ASME J. Heat Transfer
,
124
, pp.
546
–
552
.
8.
Chen
,
Y.
,
Fiebig
,
M.
, and
Mitra
,
N. K.
,
2000
, “
Heat Transfer Enhancement of Finned Oval Tubes with Staggered Punched Longitudinal Vortex Generators
,”
Int. J. Heat Mass Transfer
,
43
, pp.
417
–
435
.
9.
Chen
,
Y.
,
Fiebig
,
M.
, and
Mitra
,
N. K.
,
1998
, “
Heat Transfer Enhancement of a Finned Oval Tube With Punched Longitudinal Vortex Generators In-line
,”
Int. J. Heat Mass Transfer
,
41
, pp.
4151
–
4166
.
10.
Tiggelbeck
,
S.
,
Mitra
,
N. K.
, and
Fiebig
,
M.
,
1993
, “
Experimental Investigations of Heat Transfer Enhancement and Flow Losses in a Channel with Double Rows of Longitudinal Vortex Generators
,”
Int. J. Heat Mass Transfer
,
36
(
9
), pp.
2327
–
2337
.
11.
Torii, K., Nishino, K., and Nakayama, K., 1994, “Mechanism of Heat Transfer Augmentation by Longitudinal Vortices in a Flat Plate Boundary Layer,” Proc. of 10 Int. Heat Transfer Conf., Hemisphere, New York, Vol. 6, pp. 123–128.
12.
Lin
,
C. N.
, and
Jang
,
J. Y.
,
2002
, “
Conjugate Heat Transfer and Fluid Flow Analysis in Fin-Tube Heat Exchangers with Wave-Type Vortex Generators
,”
J. Enhanced Heat Transfer
,
9
(
3–4
), pp.
123
–
136
.
13.
TIFF Revision 6.0, 1992, Adobe Developers Association, Adobe System Inc.
14.
Ekkad
,
S. V.
, and
Han
,
J. C.
,
1997
, “
Detailed Heat Transfer Distributions in Two-Pass Square Channels With Rib Turbulators
,”
Int. J. Heat Mass Transfer
,
40
(
11
), pp.
2525
–
2537
.
15.
Incropera, F. P., and DeWitt, D. P., 1990, Fundamentals of Heat and Mass Transfer, Third, edition, Wiley, New York.
16.
Moffatt
,
R. J.
,
1988
, “
Describing the Uncertainties in Experimental Results
,”
Exp. Therm. Fluid Sci.
,
1
, pp.
3
–
17
.
17.
Petukhov, B. S., 1970, “Heat Transfer in Turbulent Pipe Flow With Variable Physical Properties,” Advances in Heat Transfer, T. F. Irvine and J. P. Hartnett, eds., Academic Press, New York, Vol. 6, pp. 504–564.
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