When is fouling relevant?

Fouling is relevant in case of a high heat transfer coefficient, usually on both sides. An example would be evaporation on the one and condensation on the other side. Both result in high heat transfer coefficients.
The same applies to high Reynolds Number flows A high Reynolds Number usually correlates with a   high heat transfer coefficient.

The explanation is relativly easy with a little knowledge in thermal process engineering. he heat transfer is determined by the resistance that must be overcome to transfer heat from on side to the next.
The resistance can be seen as a serial type of resistance (like in an electrical circuit).
Each resistance (heat transfer one side, heat conductivity wall, heat transfer outer side) effects the  heat that can be transfered. Each resistance (heat transfer one side, heat conductivity wall, heat transfer outer side) effects the  heat that can be transfered.

In case of big heat transfer coefficients the resistance is smaller compared to a small
heat transfer coefficient. With big heat transfer coefficients the contribution to the overall resistance deminishes  compared to other factors like the conductivity of the wall and fouling.

So the contribution of fouling gets relevant.

In general it is best practice to consider fouling for every calculation.
In our software for the calculation of shell-and-tube heat exchangers (WTS) or for air coolers/coil heat exchangers (AC) you can select a proper fouling factor by either clicking on the blue question mark right next to the fouling factor and using our help or by right clicking on the box for the fouling factor select value proposals.


See also:

This post is also available in: Deutsch (German)