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RESEARCH PAPERS: Evaporation, Boiling, and Condensation

Heat Transfer Performance During Condensation Inside Horizontal Smooth, Micro-Fin and Herringbone Tubes

[+] Author and Article Information
Adriaan Lambrechts

 University of Johannesburg, South Africa

Leon Liebenberg1

Department of Mechanical and Aeronautical Engineering,  University of Pretoria, Pretoria 0002, South Africalieb@up.ac.za

Arthur E. Bergles

 University of Maryland, College Park, MD 20742-3035abergles@aol.com

Josua P. Meyer

Department of Mechanical and Aeronautical Engineering,  University of Pretoria, Pretoria 0002, South Africajmeyer@up.ac.za

1

Corresponding author.

J. Heat Transfer 128(7), 691-700 (Mar 10, 2006) (10 pages) doi:10.1115/1.2194038 History: Received May 16, 2005; Revised March 10, 2006

An experimental investigation was conducted into the heat transfer characteristics during in-tube condensation of horizontal smooth, micro-fin, and herringbone tubes. The study focused on the heat transfer coefficients of refrigerants R-22, R-134a, and R-407C inside a series of typical horizontal smooth, micro-fin, and herringbone tubes at a representative average saturation temperature of 40°C. Mass fluxes ranged from 300 to 800kgm2s, and vapor qualities ranged from 0.85 to 0.95 at condenser inlet, to 0.05 to 0.15 at condenser outlet. The herringbone tube results were compared with the smooth and micro-fin tube results. The average increase in the heat transfer coefficient of the herringbone tube, when compared with the smooth tube at comparable conditions, was found to be 322%, with maximum values reaching 336%. When compared with the micro-fin tube, the average increase in heat transfer coefficient was found to be 196%, with maximum values reaching 215%. Moreover, a new correlation was developed to predict the heat transfer coefficients in a herringbone and micro-fin tube. Semi-local heat transfer coefficients were calculated from the modified Wilson plot technique, using measurements of condenser subsection inlets and outlets, and from knowledge of the temperature gradient on the annulus side. The correlation predicted the semi-local heat transfer coefficients accurately, with 96% and 89% of the data points falling in the ±20% region for the herringbone tube and the micro-fin tube, respectively. The average heat transfer coefficients were accurately predicted, too, with all the data points for the herringbone tube and 83% of the data points for the micro-fin tube falling in the ±20% region. The derived heat transfer correlations can be used for design, especially for reversible heat pumps. This research proves that predicting the flow pattern during intermittent and annular flow is not a prerequisite for predicting the heat transfer accurately to within 20% of the measurements.

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Copyright © 2006 by American Society of Mechanical Engineers
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Figures

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Figure 1

Experimental (a) micro-fin tube and (b) herringbone tube

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Figure 2

Experimental setup

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Figure 3

Experimental data and new flow regime map for R-407C condensing in a herringbone tube

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Figure 4

Flow regime observations for R-407C condensing in a herringbone tube at 300kg∕m2s, 500kg∕m2s, and 800kg∕m2s

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Figure 5

Semi-local heat transfer coefficients for herringbone tube

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Figure 6

Average heat transfer coefficients for smooth, micro-fin, and herringbone tube

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Figure 7

Experimental average heat transfer coefficients versus predicted average heat transfer coefficients for herringbone tube

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Figure 8

Average heat transfer coefficients for condensing (a) R-22 in herringbone tube, (b) R-134a in herringbone tube, and (c) R-407C in herringbone tube

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