Cooling towers are similar to the radiator in an automobile in that they use a liquid medium to carry heat away from one area and dissipate it in another. In an automobile, heat is a mostly unwanted side product of the combustion of gasoline. The heat from this combustion would melt the engine if left unchecked. The reason this doesn’t happen is that a cooling liquid, radiator fluid, is passed through the engine where it absorbs heat from the combustion chambers. The liquid is then passed to the radiator where it is cooled through various means. The cooled water is then returned to the engine to pick up more heat. In this manner, the heat from the engine is transferred to another location, keeping the engine from overheating.

Industrial processes produce high amounts of heat and that heat is dissipated in much the same way as an automobile. This can be done through a closed loop system (fin-fan), in which the liquid never directly touches open air, or open loop (cooling tower), in which the liquid is exposed to open air. When gas is compressed, it produces heat which must be dissipated before the gas can be transported. The people and electronic equipment used in large office buildings produce enough heat that it must be removed to keep a comfortable atmosphere. Chemical plants, refineries, nuclear power plants, compression stations, food processing plants, and a multitude of other areas use cooling towers. Large college complexes can be cooled using a single system through the use of water pipes collecting heat in the classrooms and dissipating it through cooling towers or fin fans.

Fin Fan

A fin fan is exactly like an automobile radiator in that it uses tubes with small projections (fins) attached. As the liquid passes through the tubes the heat is drawn to the fins where it is cooled by passing air. This arrangement is generally used when it is undesirable to expose the cooling liquid to ambient air or when the temperature or humidity of the ambient air would cause the cooling liquid to evaporate too quickly.

Cooling Tower

A cooling tower utilizes the evaporation of the cooling liquid to dissipate heat. Generally, a cooling tower has nozzles that let the cooling liquid fall into open air. The liquid is released at the top of the tower and cascades down across a series of ventilated shelves. A fan at the top of the tower draws fresh air through the ventilated shelves and across the falling water. The air cools the liquid, which is then collected, filtered, and returned to the delivery system to gather more heat.

Monitoring Solutions

440 Internal Sensor
Provides local contacts as well as a 4-20mA output for interface with a PLC / DCS or other process monitor. Precaution: Placing the switch inside the cooling tower can cause the seal to fail if the moisture inside the tower contains corrosive substances.

440 External Sensor
Provides local contacts as well as 4-20mA output for interface with a PLC / DCS or other process monitor. Electronics and setpoint controls located outside of wet area.

5535/45
Provides 4-20mA output interface with a PLC / DCS or other process monitor. Available local LCD display. Filters and galvanic isolation available. BNC output for dynamic signal analysis.

ST5485E
4-20mA output for interface with a PLC / DCS or other process monitor. High-pass and low-pass filters available. Simple 2 wire installation.