Falling Film Transitions on Plain and Enhanced Tubes

Author:

Roques J. F.1,Dupont V.1,Thome J. R.1

Affiliation:

1. Laboratory of Heat and Mass Transfer (LTCM), Department of Mechanical Engineering, Swiss Federal Institute of Technology Lausanne, CH-1015 Lausanne, Switzerland

Abstract

In falling film heat transfer on horizontal tube bundles, liquid flow from tube to tube occurs as a falling jet that can take on different flow modes. At low flow rates, the liquid film falls as discrete droplets. At higher flow rates, these droplets form discretely spaced liquid columns. At still higher flow rates, the film falls as a continuous sheet of liquid. Predicting the flow transitions between these flow modes is an essential step in determining the heat transfer coefficient for the particular flow mode, whether for a single phase process or for falling film condensation or evaporation. Previous studies have centered mostly on falling films on plain tube arrays. The objective of the present study is to extend the investigation to tubes with enhanced surfaces: a low finned tube, an enhanced boiling tube and an enhanced condensation tube. The effect of tube spacing on flow transition has also been investigated. The test fluids were water, glycol and a glycol-water mixture. The adiabatic experimental results show that the flow mode transition thresholds for the enhanced boiling tube are very similar to those of the plain tube while the fin structure of the other two enhanced tubes can significantly shift their transition thresholds.

Publisher

ASME International

Subject

Mechanical Engineering,Mechanics of Materials,Condensed Matter Physics,General Materials Science

Reference13 articles.

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2. Nusselt, W. , 1916, “Die oberfla¨chenkondensation des wasserdampfes,” Zeitschr. Ver. Deutch. Ing., 60, pp. 541–569.

3. Kern, D. Q. , 1958, “Mathematical Development of Loading in Horizontal Condensers,” AIChE J., 4, No. 2, pp. 157–160.

4. Marto, P. J. , 1986, “Recent Progress in Enhancing Film Condensation Heat Transfer on Horizontal Tubes,” Heat Transfer Eng., 7, pp. 53–63.

5. Honda, H., Nozu, S., and Takeda, Y., 1987, “Flow Characteristics of Condensation on a Vertical Column of Horizontal Tubes,” Proc. 1987 ASME-JSME Thermal Engineering Joint Conference, Honolulu, Vol. 1, pp. 517–524.

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