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TECHNICAL PAPERS: Evaporation, Boiling, and Condensation

Condensation of Ethylene Glycol on Integral-Fin Tubes: Effect of Fin Geometry and Vapor Velocity

[+] Author and Article Information
Satesh Namasivayam

Department of Engineering, Queen Mary,  University of London, Mile End Road, London, E1 4NS, UK

Department of Engineering, Queen Mary,  University of London, Mile End Road, London, E1 4NS, UKA.Briggs@qmul.ac.uk

Note that previous experimental investigations for condensation on plain tubes have shown good agreement with Shekriladze and Gomelauri (12) at low to moderate vapor velocities, but less good agreement at high velocities.

1

Corresponding author.

J. Heat Transfer 127(11), 1197-1206 (Jun 18, 2005) (10 pages) doi:10.1115/1.2039112 History: Received January 13, 2005; Revised June 18, 2005

Abstract

New experimental data are reported for forced-convection condensation of ethylene glycol on a set of nine single, copper, integral-fin tubes. The first set of five tubes had fin height and thickness of 1.6 and $0.25mm$, respectively, with fin spacings of 0.25, 0.5, 1.0, 1.5, and $2.0mm$. The second set of four tubes had fin spacing and thickness of 1.0 and $0.5mm$, respectively, and fin heights of 0.5, 0.9, 1.3, and $1.6mm$. The fins were rectangular in cross section. All tubes had a fin root diameter of $12.7mm$. A plain tube of outside diameter $12.7mm$ was also tested. The tests, which were performed at a near constant pressure of $∼15kPa$, covered vapor velocities between 10 and $22m∕s$ and a wide range of heat fluxes. The best performing tube was that with fin spacing, height, and thickness of 0.5, 1.6, and $0.25mm$, respectively, which had an enhancement ratio (compared to the plain tube at the same vapor-side temperature difference and vapor velocity) of 2.5 at the lowest vapor velocity tested, increasing to 2.7 at the highest. For all but two of the tubes, the effect of vapor velocity on the heat-transfer coefficient of the finned tubes was less than on the plain tube, leading to a decrease in enhancement ratio with increasing vapor velocity. For two of the tubes, however, the enhancement ratio increased with increasing vapor velocity, which is the opposite trend to that found in most earlier experimental studies. This effect was thought to be due to the slight reduction in condensate flooding between the fins of these two tubes because of vapor shear.

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Figures

Figure 1

Condensate flooding on a horizontal integral-fin tube

Figure 2

Apparatus

Figure 3

Test section and test condenser tube arrangement

Figure 4

(a) Plain tube results and (b) variation of heat flux with vapor-side temperature difference for the plain tube

Figure 5

Variation of heat flux with vapor-side temperature difference. Effect of fin spacing.

Figure 6

Variation of heat flux with vapor-side temperature difference. Effect of fin height.

Figure 7

Variation of heat flux with vapor-side temperature difference. Effect of vapor velocity (d=12.7mm, t=0.25mm, h=1.6mm, s as a variable).

Figure 8

Variation of heat flux with vapor-side temperature difference. Effect of vapor velocity (d=12.7mm, t=0.5mm, s=1.0mm, h as a variable).

Figure 9

Variation of enhancement ratio with vapor velocity. Effect of fin spacing.

Figure 10

Variation of enhancement ratio with vapor velocity. Effect of fin height.

Figure 11

Variation of enhancement ratio with vapor velocity. Effect of fin thickness.

Figure 12

Comparison of experimental data to model of Cavallini (9)

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