Fouling of heat exchangers is defined as the total accumulation of unwanted deposits on a heat transfer surface. Systems are known to have a foulant layer that is known to impose additional resistance during heat transfer. It is also responsible for narrowing flow areas because of deposits, which increases the velocity of volumetric flow rates.
In most cases, deposits are hydrodynamically rough, which means there is an increase in resistance to the flow of fluid that goes over the surface of the deposit. Ultimately, there is a severe consequence of fouling, which includes a reduction in exchanger efficiency, as well as excessive pressure drops through the exchanger and ammonia vaporizer.
Fouling happens rapidly in some heat exchangers. Other exchangers can run for several years before experiencing a problem. How systems run are primarily dependent upon the fluid, as well as conditions of exchanger operations. It is essential to keep in mind that the deposits types vary drastically. For instance, some deposits are hard, which makes them difficult to remove. Other accumulations range in varying softness levels. Softer deposits are easier to remove from scraped surface heat exchangers.
Scraped Surface Heat Exchangers
Deposits consist of different components. A deposit that results from cooling water tends to include adverse effects like particulate matter, corrosion products, and living biological material. The full extent of components within the deposit depends on many different factors that include the source of water, the treatment of water, and its processing conditions.