Parameters that can influence the fouling factor:
There are even more parameters that can influence the fouling factor. In general, the following conditions are known for their influence:
Velocity of the medium
Increasing medium velocity will in general increase the release rate and therefore decrease fouling.
Temperature of the bulk fluid
Especially precipitation and chemical reaction fouling can depend strongly on bulk temperature, but both in a different way.
Temperature of the heat transfer surface
Lowering this temperature may increase solidification or even precipitation fouling.
Other fouling mechanisms may increase with increasing temperature.
Surface material
The amount of corrosion is strongly dependent on the choice of the surface material.
Surface material may also influence biological fouling, e.g. copper is more sensitive to biological fouling then most other materials.
Heat exchanger configuration
From experience it’s known that shell-and-tube heat exchangers are more sensitive to fouling than for example a plate-and-frame or double-piped heat exchangers. This is mostly because velocities and turbulence levels are higher for the latter one. Disadvantage of these heat exchangers is that they’re far bigger than a shell-and tube with the same capacity.
It’s clear that the precise influence of each of these conditions on the fouling factor depends on the type of fouling. In some cases this precise influence isn’t known yet, and there’s still a lot of research done. Still, understanding the impact of these conditions on the fouling resistance is essential to actually control fouling-phenomena, and thereby control the costs. In the design of a new heat exchanger, one must be aware of all the mentioned conditions and other influences of fouling factors, and choose those conditions that will result in as less fouling as possible. One must also be aware that it must be possible to clean a heat exchanger once in a while, which will have impact on the chosen construction.
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