Method of heat and mass transfer enhancement in film evaporation

✍ Scribed by G.S. Zheng; W.M. Worek

• Publisher: Elsevier Science
• Year: 1996
• Tongue: English
• Weight: 895 KB
• Volume: 39
• Category: Article
• ISSN: 0017-9310
• DOI: 10.1016/s0017-9310(96)85009-5

✦ Synopsis

Combined heat and mass transfer processes that occur when water evaporates from a flowing film have been investigated. The major emphasis of this work studied methods to enhance heat and mass transfer rates from the film. A fiber-optic holographic interferometer was used to measure the local heat and mass transfer coefficients from the air-liquid interface, and a set of thermocouples and a dewpoint hygrometer were used to measure the average heat and mass transfer rates in the system. First, without utilizing any enhancement techniques. the local and average transfer rates from the water solution were determined, then a mechanical method for enhancing the heat and mass transfer rates was investigated.

In this method, 2 mm glass rods were used to disturb the liquid film flow, which also disturbed the flow of the air stream. The local temperature and concentration distributions were calculated and used to evaluate the local Nusselt and Sherwood numbers. It was observed that average Nusselt number Nu,,. and average Sherwood number S/I,,, for the water solution have a maximum which depends on the pitch of the glass rods.