Filmwise condensation of steam on low integral-finned tubes

Abstract

Filmwise condensation heat-transfer measurements if steam were made on horizontal tubes under vacuum and near-atmospheric pressures. Data were taken for a smooth tube and for 21 tubes which contained rectangularly-shaped, low integral fins. The fin geometry was systematically varied in order to investigate the dependence of the steam-side heat-transfer coefficient on fin spacing, thickness and height. The condensation process was found to be most sensitive to fin spacing and to be weakly dependent on fin thickness. When the fin height was increased from1.0 to 2.0 mm, the increase in the heat-transfer coefficient was about 20 percent, while the increase in condensing area was 51 percent. The best performing finned tube had a fin spacing of 1.5 mm, a fin thickness of 1.0 mm and a fin height of 2.0 mm. It showed an enhancement over the smooth tube of between 4 to 5 under vacuum conditions and around 6 at atmospheric conditions. Thus, the use of finned tubes may result in a significant reduction in the size and weight of present-day steam condensers.