Falling Film Transitions Between Droplet, Column, and Sheet Flow Modes on a Vertical Array of Horizontal 19 FPI and 40 FPI Low-Finned Tubes
Titel:
Falling Film Transitions Between Droplet, Column, and Sheet Flow Modes on a Vertical Array of Horizontal 19 FPI and 40 FPI Low-Finned Tubes
Auteur:
Roques, Jean-Francois Thome, John R.
Verschenen in:
Heat transfer engineering
Paginering:
Jaargang 24 (2003) nr. 6 pagina's 40-45
Jaar:
2003-11
Inhoud:
Intertube flow modes for falling film condensers and evaporators with plain and enhanced horizontal tube bundles are thought to have a key influence on their tube row effects. Three principal types of flow modes are typically observed—droplet mode, column mode, and sheet mode—together with intermediate modes—coexistence of droplet-column modes and of column-sheet modes. All act as falling jets from the upper tube onto the tube directly below. In a previous study by Roques, Dupont, and Thome [1], the transitions between these intertube flow modes were observed and measured for rows of plain tubes, Thermoexcel-C enhanced condensing tubes, Turbo-Bii enhanced boiling tubes, and 26 fpi (1024 fpm) low-finned tubes for water, glycol, and a 50/50 water-glycol mixture. Significant differences were observed in the transition thresholds for these tube surface geometries. In the present study, this investigation has been extended to 19 fpi and 40 fpi (748 and 1575 fpm) low-finned Wieland tubes. A comparison between plain, 19 fpi, 26 fpi, and 40 fpi tubes in the present study shows similar transition thresholds between the high fin density (40 fpi) tube and plain tube but significantly higher transition thresholds for the 19 fpi and 26 fpi tubes.
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