Transient Evaluation of Process Surfaces Used in Fouling Applications

摘要

Fouling is an important and complex problem that affects a variety of industries. Surface fouling takes place as a result of the complex reactions that cause deposits to form on process surfaces. A number of parameters influence fouling development, including flow velocity, surface temperature, surface material/finish, surface geometry, and fluid properties. It is a transient process that begins with a clean process surface and may progress until the surface can no longer be used effectively. The event sequence of the fouling process appears in general to be universal, beginning when fluid comes into contact with a process surface. During this induction period, a conditioning film forms, and the heat transfer efficiencies do not change significantly. Conditioning film appearance may occur in weeks, days, or minutes. This stage is followed by a rapid accumulation of deposit growth. It is during this growth phase that the heat transfer across the process surface starts to dramatically change. Finally, a pseudo-steady-state period is arrived at when accumulation is almost constant. This accumulation causes heat transfer to significantly decrease and a complete cleaning of the surfaces may be required. Included here is a discussion on process surface materials used in applications where fouling may be a concern. Previous work in this area has prompted this study in order to provide better information for designs involving fouling. Conclusions and observations regarding the materials/surfaces that are commonly used in designs where fouling may be a concern are presented here. Photographs are presented of frontal surfaces and edges. Finally, transient surface roughness values are given for several materials.