For the commonly used five ink heat exchanger, according to the scaling mechanism, the fouling is generally divided into the following categories:

        (1) Crystallization fouling: refers to the fouling formed on the surface of graphite heat exchanger by crystallization of inorganic salts dissolved in supersaturated flowing liquid, which is called crystallization fouling. Scale is a common scale in industrial equipment. In the water cooling system, the supersaturated calcium and magnesium salts in the water crystallize and deposit on the surface of graphite heat exchanger due to the changes of temperature and pH in the water.

        (2) Particulate fouling: the accumulation of suspended solid particles such as sand, dust and carbon black on the heat transfer surface in a fluid system.

        (3) Chemical reaction fouling: deposit formation between heated surface and fluid due to self oxidation and polymerization, i.e. chemical reaction.

        (4) Corrosive fouling: due to the corrosive or corrosive impurities in the fluid, the heat exchange surface is corroded, and the corrosion products are deposited on the heat exchange surface to form dirt.

        (5) Biofouling: it is a kind of sticky sediment formed by the adhesion of microbial community and its excreta, chemical pollutants, mud and other components on the wall surface of heat exchange pipe and pipeline, which is called biological fouling.

        (6) Solidification fouling: fouling formed by solidification and deposition of high dissolved components of clean liquid or multicomponent solution on supercooled heat exchange surface. Fouling is often the result of a variety of processes and mutual influence, the actual fouling on the heat exchange surface is often mixed with a variety of fouling.