Cooling Tower Terms

Ambient Temperature - The DBT as measured by a thermometer.

Axial Fans - Fans in which the direction of the airflow does not change. Axial fan types include propeller, tubaxial and vaneaxial.

Blowdown - Water removed from a cooling tower to prevent excessive buildup of impurities within the system. Impurities increase in concentration as water evaporates during the cooling process.

Blow Out - Water removed from a cooling tower through wind or splashing. Blow out is reduced or eliminated through the use of screens and other mechanisms.

BTU (British Thermal Unit) - The amount of heat gain or loss that is needed in order to change the temperature of one pound of water by one degree Fahrenheit.

Drift - Water droplets removed from a cooling tower along with the exhaust air. Drift must be controlled because, unlike the water vapor removed from the tower, drift often contains chemicals, debris and other impurities that may negatively affect the environment.

Drift Eliminator - A mechanism in a cooling tower that prevents drift from leaving the tower by catching the drift as it flows through the eliminator, while allowing the passage of exhausted air through the eliminator and into the atmosphere.

Dry Bulb Temperature (DBT) - The temperature of the air entering the cooling tower, measured in degrees Fahrenheit.

Entrainment - Water in the air being brought into the cooling plumes as the liquid wastes are discharged.

Exhaust Air - The air removed from the cooling tower during the cooling process. Exhaust air also contains water vapor that has evaporated during the cooling process.

Fill - A labyrinth-like packing that provides a vastly expanded air-water interface, which allows heating of the air and evaporation to occur. Film fill consists of multiple, typically vertical, wetted surfaces upon which a thin covering of water spreads, while splash fill consists of many levels of horizontal splash elements that create a cascade of tiny droplets, which have a large combined surface area.

Fogging - The foggy condensation of water vapor outside of a cooling tower resulting from the contact of saturated exhaust air emerging from the tower with cooler air outside of the tower.

Induced Draft - The process in which the fan of the cooling tower draws air from the bottom of the unit and passes it out through the top of the cooling tower.

Noise - Sound energy generated by the impact of falling water, movement of air by fans, the movement of fan blades within the structure and the drive belts, gearboxes and motors that is emitted by a cooling tower and recorded at a certain distance and direction.

Nozzle - A mechanism through which water flows into a cooling tower in either spray or stream form.

Plume - Exhaust air and water vapor emerging from a cooling tower. A plume may create fogging when introduced to air of a lower temperature.

Psychrometer - Mechanism used in a cooling tower system to measure the wet bulb temperature of the system.

Recirculation - The entrance into a cooling tower of previously discharged air that reenters the system along with fresh air.

Thermal Capacity - Cooling tower capacity representing the amount of liquid, measured in gallons per minute, that a cooling tower can process.

Wet Bulb Temperature (WBT) - The temperature within a cooling tower at which the air is saturated with water vapor, preventing the further occurrence of water evaporation.