Condensation heat transfer and flow characteristics of R-134a flowing through corrugated tubes
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Author list: Laohalertdecha S., Wongwises S.
Publisher: Elsevier
Publication year: 2011
Journal: International Journal of Heat and Mass Transfer (0017-9310)
Volume number: 54
Issue number: #
Start page: 2673
End page: 2682
Number of pages: 10
ISSN: 0017-9310
eISSN: 1879-2189
Languages: English-Great Britain (EN-GB)
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Abstract
This article presents the condensation heat transfer and flow characteristics of R-134a flowing through corrugated tubes experimentally. The test section is a horizontal counter-flow concentric tube-in-tube heat exchanger 2000 mm in length. A smooth copper tube and corrugated copper tubes having inner diameters of 8.7 mm are used as an inner tube. The outer tube is made from smooth copper tube having an inner diameter of 21.2 mm. The corrugation pitches used in this study are 5.08, 6.35, and 8.46 mm. Similarly, the corrugation depths are 1, 1.25, and 1.5 mm, respectively. The test conditions are performed at saturation temperatures of 40-50 ฐC, heat fluxes of 5-10 kW/m 2, mass fluxes of 200-700 kg/m2 s, and equivalent Reynolds numbers of 30000-120000. The Nusselt number and two-phase friction factor obtained from the corrugated tubes are significantly higher than those obtained from the smooth tube. Finally, new correlations are developed based on the present experimental data for predicting the Nusselt number and two-phase friction factor for corrugated tubes. ฉ 2011 Elsevier Ltd. All rights reserved.
Keywords
Nusselt number, Two-phase friction factor
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