BK1-6 Enhanced Boiling Surfaces as Single Tubes and Tube Bundles

S. B. Yilmaz and J. W. Palen

Two types of re-entrant cavity enhanced surface tubes and a low-finned tube were tested in reboiler bundles and compared to an identical plain tube bundle for boiling light hydrocarbons over a range of pressures. The two enhanced tubes and the plain tube were also tested as single tubes in pool boiling.

In general, the enhanced tubes produced significantly higher heat transfer rates than the plain tubes at the same temperature difference, and produced boiling down to much lower temperature differences than the plain tubes. The amount of enhancement in heat transfer was less for the bundles than for the single tubes, due to superimposed convection effects in the bundles which are not further enhanced by increasing the nucleation properties of the surface. In addition, the amount of enhancement was affected by heat flux, system pressure, fluid properties, and mixture boiling range.

It was not possible to produce a meaningful method at this time due to the many variables involved, the small amount of data, and the limited knowledge and background presently available. However, some general concepts and overall guidelines were deduced which should be useful for future work. Manufacturers' recommendations must presently be followed for design, but as more potential applications become apparent, effort should be directed toward additional data and generalized design methods.