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Mechanical / HVACaka: evaporative cooling toweraka: CT

Cooling Tower

In Plain English

A large evaporative heat exchanger on a roof or ground that cools water returning from a chiller.

Definition

A heat rejection device that removes heat from condenser water by evaporating a portion of the water to the atmosphere, cooling the remainder. Cooling towers are used with water-cooled chillers to reject heat that has been extracted from the building's chilled water system. They are characterized by approach temperature (difference between leaving water temperature and entering wet-bulb temperature) and cooling capacity in tons.

Why It Matters in Bidding

Cooling towers are major mechanical line items whose price, rigging, structural support, and water and electrical connections all flow into the HVAC estimate, and they often sit on the critical path because of long lead times and crane picks. Misjudging the tonnage, basin heater, or structural and screening requirements can leave significant scope and coordination cost unaccounted for when the mechanical sub finalizes its bid.

Example

Pricing a chiller plant replacement, the mechanical estimator includes the cooling tower unit, a roof structural curb, a crane pick for the rooftop set, makeup water and condenser piping, and freeze-protection controls in the bid.

Related Terms

ChillerChilled Water SystemHeat ExchangerCondensing Unit

Frequently Asked Questions

Beyond the tower, estimators must account for structural support or a curb, vibration isolation, crane or rigging for placement, condenser water piping and pumps, makeup and bleed water lines, electrical feeds and controls, basin heaters or freeze protection, and water treatment. Long lead times also push it onto the critical path, affecting schedule and general conditions.
Approach is the difference between the cooling tower's leaving water temperature and the ambient wet-bulb temperature; a smaller approach requires a larger, more expensive tower. The specified approach drives the unit selection the manufacturer prices, so estimators should confirm the design basis in the specifications before assuming a vendor quote covers the required performance.
Both are rated in tons, but a cooling tower must reject more heat than the chiller's cooling load because it also handles the heat added by the compressor, so a nominal cooling-tower ton represents more heat rejection. Matching the tower rating to the condenser-water flow and the chiller's heat-rejection requirement prevents undersizing.

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