Instability of film coating of wires and tubes

✍ Scribed by S. P. Lin; W. C. Liu

• Book ID: 102695085
• Publisher: American Institute of Chemical Engineers
• Year: 1975
• Tongue: English
• Weight: 791 KB
• Volume: 21
• Category: Article
• ISSN: 0001-1541
• DOI: 10.1002/aic.690210420

✦ Synopsis

Abstract

The stability problem of the free coating of wires and tubes by withdrawal is formulated and solved. The necessary condition for the stability of the film coating is given explicitly in terms of the Reynolds number, wave number, the Weber number, and implicitly in terms of the withdrawal velocity. The outcome of the competition between the destabilizing capillary pinching and the stabilizing capillary restoring force associated with the film thickness variation is shown to dictate the stability of the film. The comparisons between the present theoretical results and the known experimental results for falling films and creeping annular threads of viscous liquids are good. A possible application of the present results to some aspects of the qualitative design of a coating process is given.