**2.3 Fouling by corrosion**

This type of fouling occurs as a result of electrochemical or microbial corrosion of a surface in contact with a fluid (**Figure 4**). The composition of corrosion products is normally a function of the material from which they originate. According to [12] corrosion must be taken into account in the design of heat exchangers in order to generate more information on the thermal resistance associated with fouling by corrosion.

#### **2.4 Freezing fouling**

It is the accumulation of solid deposits on a refrigerated surface due to the solidification of a fluid or one of its constituents. The accumulation of this type of fouling depends on the temperature of the surface and the shearing effect produced by the fluid on the surface as a function of its velocity of circulation [13, 14]. This phenomenon is seen in the solidification of the wax, whose melting point is high, in a hydrocarbon solution on a heat exchange surface (**Figure 5**).

#### **Figure 3.**

*Residue of hydrocarbon in the tubes of a heat exchanger (Source: By courtesy of H&C Heat Transfer Solutions Inc. 2013).*

#### **Figure 4.**

*Oxides of corrosion in the tubes of a heat exchanger (H&C Heat Transfer Solutions Inc. 2013).*

**Figure 5.**

*Icy icing of polymer products in a heat exchanger (Source: By courtesy of H&C Heat Transfer Solutions In.).*

#### **2.5 Fouling by precipitation**

The origin of this type of fouling is the precipitation or scaling of dissolved substances on the surfaces. Precipitation usually occurs from aqueous solutions based on their temperature and the solubility of dissolved substances, such as calcium carbonate (CaCO3), whose precipitation of the solution occurs on a superheated surface when the water contained in the water evaporates (**Figure 6**).

The precipitation of the salts dissolved in the water originates when coming into contact with the wall of the hot tube and supersaturation occurs. The deposits adhered to the surface may have different hardness depending on their composition. Thus, when the deposit is only composed of salts, it is hard and very adherent. On the other hand, if the deposit is a mixture of salts and suspended solids, its hardness is low, and they adhere weakly [15].

**67**

*Inc).*

**Figure 6.**

*Fouling in Heat Exchangers*

• Calcium carbonate

• Calcium sulfate

• Calcium oxalate

• Barium sulfate

• Silicates

• Copper

• Phosphates

• Magnetite

• Magnesium hydroxide

• Aluminum oxides

• Aluminum silicate

with water of high hardness.

called sedimentation (**Figure 7**) [17].

**2.6 Fouling by particles**

These precipitates are very common in boilers and heat exchangers that operate

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

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

*DOI: http://dx.doi.org/10.5772/intechopen.88079*

The precipitates usually observed in industrial facilities that use aqueous solutions are the following [16]:

*Fouling in Heat Exchangers DOI: http://dx.doi.org/10.5772/intechopen.88079*


*Inverse Heat Conduction and Heat Exchangers*

**66**

**2.5 Fouling by precipitation**

**Figure 4.**

**Figure 5.**

hardness is low, and they adhere weakly [15].

solutions are the following [16]:

The origin of this type of fouling is the precipitation or scaling of dissolved substances on the surfaces. Precipitation usually occurs from aqueous solutions based on their temperature and the solubility of dissolved substances, such as calcium carbonate (CaCO3), whose precipitation of the solution occurs on a superheated

*Icy icing of polymer products in a heat exchanger (Source: By courtesy of H&C Heat Transfer Solutions In.).*

The precipitation of the salts dissolved in the water originates when coming into contact with the wall of the hot tube and supersaturation occurs. The deposits adhered to the surface may have different hardness depending on their composition. Thus, when the deposit is only composed of salts, it is hard and very adherent. On the other hand, if the deposit is a mixture of salts and suspended solids, its

The precipitates usually observed in industrial facilities that use aqueous

surface when the water contained in the water evaporates (**Figure 6**).

*Oxides of corrosion in the tubes of a heat exchanger (H&C Heat Transfer Solutions Inc. 2013).*


These precipitates are very common in boilers and heat exchangers that operate with water of high hardness.
