Negative fouling resistances: The effect of surface roughness

✍ Scribed by B.D. Crittenden; N.J. Alderman

• Publisher: Elsevier Science
• Year: 1988
• Tongue: English
• Weight: 727 KB
• Volume: 43
• Category: Article
• ISSN: 0009-2509
• DOI: 10.1016/0009-2509(88)80078-2

✦ Synopsis

The limiting diffusion current technique has been used to study the effect of deposit characteristics on mass transfer rates in a simple mixing cell. The presence of particles on the cathode has two effects on mass transfer rates. Firstly, the resistance to mass transfer through the deposit increases with the number of particle layers. Secondly, the presence of particles, large with respect to the original roughness of the unfouled surface, reduces the resistance to mass transfer through the fluid film at the fluid-deposit interface. At relatively high Reynolds numbers the latter effect can predominate to such an extent that the overall resistance to mass transfer can become less than that of the unfouled surface. The application of these findings to the analogous case of heat transfer across a fouled surface explains the existence of apparently negative fouling resistances which are often observed shortly after start-up from clean conditions.