A. Processes involved in fouling

Fouling of heat transfer surfaces is made up of at least five distinct processes, each of which may be subjected to analysis (Somerscales, 1981). These are:

1. Processes in the body of the fluid.
2. Transport to the heat transfer surface.
3. Attachment or formation of the deposit at the heat transfer surface.
4. Removal of material from the heat transfer surface by dissolution (material leaves in ionic form), erosion or re-entrainment (material leaves in particulate form), or spalling or sloughing (material leaves as a large mass).
5. Transport of removed material into the body of the flowing fluid.

Epstein (1983) classified the processes in five main categories — initiation, transport, attachment, removal, and aging — and combined these in a 5 × 5 matrix that includes the five main types of fouling. Figure 1 shows the matrix and the areas that have received the most and the least attention from the standpoint of research. A research goal should be to fill in our knowledge in all 25 spaces of the matrix.

Figure 1 The 5 × 5 fouling matrix. From Epstein (1983)