Doubly fluted tubes

An important large-scale test of a doubly fluted tube for OTEC condenser service was reported by Lewis and Sather [162]. The tube is the same one noted earlier under enhancement of falling-film evaporation [136]. The ammonia-side heat transfer coefficient was enhanced several times to a value of 3730 Btu/(h-ft2-°F), or 21,181 W/(m2-K). 

With falling film evaporation inside vertical tubes, Thomas and Young [135] found that heat transfer coefficients could be increased by more than a factor of 10 with loosely attached internal fins. While distorted tubes (e.g., doubly fluted and spirally corrugated) have been... 

The enhancement of vertical condensers remains an area of high interest due to potential large-scale power and process industry applications, for example, desalination, reboilers, and OTEC power plants. Tubes with exterior longitudinal fins or flutes, spiral flutes, and flutes on both the interior and exterior (doubly fluted) have been developed and tested. The common objectives are to use the Gregorig effect to create thin-film condensation at the tips of the flutes and to drain effectively. 

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