six fairly distinct categories. First is crystallization—the most common type of fouling that occurs in many process streams, particularly cooling-tower water. Frequently superimposed with crystallization is sedimentation, which usually is caused by deposits of particulate matter such as clay, sand, or rust. From chemical reaction and polymerization often comes a buildup of organic products and polymers. The surface temperature and presence of reactants, particularly oxygen, can have a very significant effect. Coking occurs on high-temperature surfaces and is the result of hydrocarbon deposits. Organic material growth usually is superimposed with crystallization and sedimentation and is common to sea water systems. And corrosion of the heat-transfer surface itself produces an added thermal resistance as well as a surface roughness.

In the design of the plate heat exchanger, fouling due to coking is of no significance since the unit cannot be used at such high temperatures. Corrosion also is irrelevant since the metals used in these units are noncorrosive. The other four types of fouling, however, are most important. With certain fluids such as cooling-tower water, fouling can result from a combination of crystallization, sedimentation, and organic material growth.

The Mediterranean Diet Meltdown

The Mediterranean Diet Meltdown

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