ABSTRACT
This chapter considers augmentation techniques for internal forced flows. Augmentation techniques used in external condensation are generally applicable to condensation inside tubes, but stratification of the flow by gravity needs to be considered at low vapor velocities in horizontal tubes. The basic concept behind enhanced condensation heat transfer is to reduce the condensate film thickness. When fins are attached to the inner walls of the tube or when inserts are installed, the flow path becomes longer than for a plain tube, resulting in an increase in heat transfer. Royal and Bergles tested the effects of tube inclination, twisted tape inserts, and internally finned tubes on condensation heat transfer with low-pressure steam. Their results showed that the internally finned tubes were most effective in augmenting heat transfer. Royal and Bergles also investigated the augmentation of horizontal intube condensation by means of twisted tape inserts and internally finned tubes.
