Enhanced film condensation of steam on spirally fluted tubes

✍ Scribed by N.H. Aly; S.D. Bedrose

• Publisher: Elsevier Science
• Year: 1995
• Tongue: English
• Weight: 377 KB
• Volume: 101
• Category: Article
• ISSN: 0011-9164
• DOI: 10.1016/0011-9164(95)00033-x

✦ Synopsis

Film condensation of stagnant water vapor on both vertical and horizontal spir~ly fluted robes was studied theoretically. A sine flute was taken as a typical example. In the analysis two regions of the flute, namely the valley and the crest, are treated separately. The condensation process takes place on the crest of the flute and runs down to the valley by surface tension aud gravity. In the valley region no heat transfer occurs, and the condensate moves down stream by gravity to be drained. The equation of motion and energy balance are used to conclude relations between condensate flow rate and film thickness for both regions. By equating the condensation rate in the crest region to the change of flow rate in the valley region, the film thickness and 'he local heat transfer coefficient are calculated using numerical integra~on. The average heat transfer coefficient and Nusselt cumbers are calculated and compared to that of smooth robes. The results show that the enhancemem due to fluting may reach live times in the case of horizontal tubes, while for vertical tubes it is much .lower. The the~retical results are compared to the available experimental results of film condensation on ll~rizontal finned tubes and twisted vertical tubes, which are very similar to spirally fluted tubes, and the:; ~how good agreement.