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What Is a Cooling Tower? | Process Engineering Glossary
What Is a Cooling Tower?
A cooling tower is a heat rejection device that removes waste heat from a cooling water system by transferring it to the atmosphere, primarily through the evaporative cooling of a portion of the circulating water. As warm water is distributed across the tower and contacts a flow of ambient air, a small fraction evaporates, carrying away a disproportionate amount of heat and cooling the remaining water before it returns to the process.
Because evaporative cooling can bring water temperature close to the ambient wet-bulb temperature, cooling towers can achieve significantly lower cooling water temperatures than would be possible with air-cooled heat rejection alone, particularly in humid climates where the distinction matters less, or dry climates where it matters more.
Applications of Cooling Tower
Power Plant and Refinery Heat Rejection
Large industrial facilities such as power plants and refineries rely on cooling towers to reject the substantial waste heat generated by their processes, since evaporative cooling towers can handle far greater heat loads than air-cooled alternatives of comparable size.
HVAC and Process Cooling
Cooling towers support both building HVAC systems and general process cooling needs, providing the cooling water used throughout a facility’s heat exchangers and condensers.
Water Treatment and Blowdown Management
Because evaporation concentrates dissolved solids in the recirculating water, cooling towers require ongoing blowdown, discharge of a portion of the concentrated water, along with makeup water addition and chemical treatment to manage water chemistry.
Benefits of Knowing Cooling Tower
Achieves lower cooling water temperatures. Evaporative cooling allows cooling towers to approach ambient wet-bulb temperature, generally achieving lower cooling water temperatures than dry air-cooled systems.
Handles large heat rejection loads efficiently. Cooling towers can reject substantial heat loads in a relatively compact footprint compared to equivalent air-cooled heat rejection equipment.
Widely applicable across industries. The same basic evaporative cooling principle serves power generation, refining, chemical processing, and building HVAC applications alike.
Limitations to Consider
Significant water consumption. Evaporative cooling inherently consumes water, which needs to be replaced as makeup, an important consideration in water-scarce regions or during drought conditions.
Requires water treatment to manage chemistry. Concentrating dissolved solids through evaporation requires ongoing chemical dosing and blowdown management to prevent scaling, corrosion, and biological growth.
Performance depends on ambient wet-bulb temperature. Cooling tower performance varies with ambient humidity and temperature, meaning achievable cooling water temperature isn’t constant across all weather conditions.
Cooling Tower FAQ
How does a cooling tower relate to the broader cooling water system?
A cooling tower is the heat rejection component within a broader cooling water system, which also includes the piping, pumps, and heat exchangers that circulate water between the tower and the process equipment being cooled.
Why is chemical dosing important for cooling tower operation?
Because evaporation concentrates dissolved solids, a chemical dosing system is essential for controlling scaling, corrosion including crevice corrosion, and biological growth in the recirculating water.
How does cooling tower performance affect a facility’s overall energy balance?
Cooling tower heat rejection capacity directly affects how much waste heat a facility’s heat exchanger design across the site can handle, an important input to the facility’s overall energy balance and broader heat transfer and equipment sizing planning around any associated storage tank for makeup water.
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