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Cooling system dynamics and control.While cooling systems are often treated as poor relations in an industrial plant,they are at the heart of operations and the whole plant can be dependent on asingle cooling system.

The cooling water systemis a loss loop. Water startsin the BASIN at the bottomof the cooling tower. Itflows into a smaller COLD-WELL into which additivesgo and from which water ispumped to go throughHEAT EXCHANGERS.There will probably bemany heat-exchangers inparallel or series paths ofvarious lengths. Return

water goes past a BLOW-DOWN valve which allows water to be taken out ofsystem. Then on to top of tower to meet Fanned rising AIR and loose heat byevaporation in falling down into the BASIN.

The use of evaporative cooling, as in a tower, causes build up of saltconcentrations in the cooling water. Drawing off some of this briny water andmaking up the losses controls how salty it becomes. Such blow down, ofcourse, also removes some of the chemical additives put in to inhibit corrosionand fouling.Sometimes, when clean water is scare, desperate measures are taken usingdirty water for circulation in the cooling system. It may keep the plant cool, butthe problems of fouling and loss of thermal efficiency cost money.The time scales for change are generally long and watching such processes isboring and may get insufficient attention.

Simulation Model with SCADAMcCann created a model of a complete cooling cycle system in which heatloads, atmospheric conditions, circulation rates and chemical inhibitoradditions and attrition or depletion were included to show the dynamicbehavior of the buildup of both the fouling and dissolved solids.This was then linked to a programmable model of a proposed monitoring andcontrol scheme (SCADA) based on using guidelines given by an expert tocontinuously monitor the process and make adjustments to the correctivefeeds to keep the process working properly.

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