**2.6 Fouling by particles**

It is the accumulation of solid particles that are suspended in a fluid (liquid or gas). The particles are deposited on surfaces by means of various mechanisms, some of which are closely linked to properties of particles as specific as coagulation. The amount of deposit and the rate of accumulation on the surfaces depend on the size and nature of the particles, as well as the environmental conditions. When gravity is the main mechanism of deposition of suspended particles on a surface, fouling is called sedimentation (**Figure 7**) [17].

#### **Figure 6.**

*Precipitated salts in the tubes of a heat exchanger (Source: By courtesy of H&C Heat Transfer Solutions Inc).*

#### **Figure 7.**

*Accumulation of solid particles in the plate of a tubular heat exchanger (Source: By courtesy of AH&C Heat Transfer Solutions Inc.).*
