A cooling tower rejects heat from warm circulating water by bringing that water into contact with moving air. The right selection depends on the heat load, entering and leaving water temperatures, outdoor wet-bulb condition, water quality, circuit arrangement, airflow, noise limits, maintenance access, and the heat exchanger connected to the tower. This guide turns those inputs into a practical specification and RFQ that an equipment supplier can review.
What a cooling tower actually does
In an open cooling tower, warm water is distributed over fill while air moves through the tower. A small portion of the water evaporates, carrying away heat from the remaining water. The cooled water collects in a basin and returns to a condenser, process heat exchanger, or other load. A closed-circuit tower uses the same evaporative air side, but the process fluid stays inside a coil, so the spray water and process fluid do not mix.
ASHRAE cooling tower definition is a useful starting point because it describes the equipment as a heat-transfer device in which atmospheric air cools warm water, generally through direct contact and evaporation. That definition also explains why a tower is not simply a large fan. The water distribution, fill, drift control, basin, fan, heat exchanger, and treatment program all affect the delivered result.
Three temperatures should be written down before any model is compared:
- Range is the entering water temperature minus the leaving water temperature. It describes how much the circulating water is cooled across the tower.
- Approach is the leaving water temperature minus the entering-air wet-bulb temperature. A smaller approach normally requires more heat-transfer surface, airflow, or both.
- Design wet bulb is the outdoor moisture condition used for the design point. Dry-bulb temperature alone cannot describe the evaporative potential of the air.
The design point is only one part of the duty. Ask the supplier to show turndown performance, fan control behavior, winter operation, and the water flow at the actual process load. A tower that meets a single nameplate condition may still be difficult to control when the connected refrigeration plant is lightly loaded.
Cooling tower types that change the selection
Tower terminology can feel crowded because classifications overlap. A unit can be factory-assembled, induced-draft, counterflow, and closed-circuit at the same time. The SPX classification guide separates construction, draft, airflow direction, and circuit arrangement so that each choice can be discussed independently.
The table below is a first-pass screen, not a final equipment schedule.
| Selection axis | Common choices | What changes for the buyer | Questions to carry into the RFQ |
|---|---|---|---|
| Circuit | Open or closed | Whether process fluid contacts tower air and spray water; fouling and treatment boundary | What fluid is inside the tower coil, and what cleanliness level is required? |
| Черновик | Natural, induced, or forced | Fan location, plume behavior, sound path, and service access | Where can the fan discharge or inlet be located, and what noise limit applies? |
| Air and water path | Crossflow or counterflow | Tower footprint, distribution arrangement, access to fill and nozzles | Is the available footprint fixed, and how will the distribution system be inspected? |
| Конструкция | Factory assembled or field erected | cURL Too many subrequests by single Worker invocation. To configure this limit, refer to https://developers.cloudflare.com/workers/wrangler/configuration/#limits | cURL Too many subrequests by single Worker invocation. To configure this limit, refer to https://developers.cloudflare.com/workers/wrangler/configuration/#limits |
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| Ввод | Минимальная информация, которую необходимо предоставить | Почему это важно | cURL Too many subrequests by single Worker invocation. To configure this limit, refer to https://developers.cloudflare.com/workers/wrangler/configuration/#limits |
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Sizing checks an engineer can reproduce
Tower selection software is useful, but the output should be understandable without proprietary screens. Ask for the heat balance, water flow, range, approach, wet-bulb condition, fan power, sound estimate, and the assumptions used for fouling or water quality.
Use this sequence during design review:
- Confirm the heat load at normal and peak conditions, including heat added by pumps or auxiliary equipment when relevant.
- Confirm the water flow and temperature range that the connected heat exchanger can actually deliver.
- Apply the site design wet bulb and altitude, then check the approach at the leaving-water target.
- Compare one-cell and multi-cell options so that maintenance can occur without losing the whole heat-rejection function.
- Check fan turndown, motor speed, minimum flow, basin level, and controls at low load.
- Check the effect of water treatment, fouling, drift eliminators, and fill condition on the stated rating.
The result should include a control narrative. It should explain when fans stage, how variable-speed drives respond, how makeup and blowdown are enabled, what happens on high basin conductivity, and how the tower is protected during a freeze event. A selection sheet without a control narrative leaves important operating risk to the installer.
Water treatment, drift, and Legionella controls
Evaporative equipment needs an operating water-management plan. As water evaporates, dissolved solids concentrate in the basin. Makeup water replaces evaporation and blowdown removes a controlled portion of concentrated water. EPA WaterSense guidance explains why cycles of concentration, conductivity, makeup, and blowdown should be considered together rather than adjusted independently.
CDC cooling-tower module and OSHA guidance both emphasize that warm, aerosol-producing systems need documented cleaning, treatment, inspection, and operating controls. This article is not a site health plan. Use your facility’s water-management program, local requirements, and qualified specialists for risk assessment and response.
| Water-management item | What to define in the specification | Field evidence to keep |
|---|---|---|
| Chemistry limits | Conductivity or cycles target, pH, hardness, corrosion control, and biocide approach | Trend logs, laboratory results, and treatment adjustments |
| Makeup and blowdown | Valve sizes, meter or conductivity control, drain routing, and alarm points | Commissioning records and controller set points |
| Drift control | Drift eliminator type, access, inspection interval, and replacement method | Inspection checklist and replacement records |
| Очистка | Basin, fill, nozzles, strainers, and dead-leg cleaning frequency | Dated cleaning record with responsible person |
| Freeze and idle periods | Drainage, heat trace, low-temperature sequence, and restart checks | Seasonal procedure and restart sign-off |
Do not accept “chemical treatment included” as a complete answer. Request the water analysis assumptions, dosing points, filtration arrangement, conductivity control logic, blowdown destination, and the person responsible for maintaining the program. Also ask how the tower is isolated during cleaning and how stagnant branches are avoided.
Fan energy, noise, and service access
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| Доказательства запроса ценового предложения (RFQ) | Необходимые сведения | cURL Too many subrequests by single Worker invocation. To configure this limit, refer to https://developers.cloudflare.com/workers/wrangler/configuration/#limits | Вопрос о приемке |
|---|---|---|---|
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Часто задаваемые вопросы
What is a cooling tower?
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What is the difference between open- and closed-circuit cooling towers?
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How do crossflow and counterflow towers differ?
Crossflow towers move air horizontally across falling water. Counterflow towers move air upward opposite the downward water path. The choice affects footprint, distribution hardware, access, fan arrangement, and service work. Compare the actual site layout and maintenance plan instead of assuming one airflow direction is always superior.
How do I size a cooling tower?
Start with normal and peak heat load, entering and leaving water temperatures, water flow, design wet bulb, altitude, and site restrictions. Then compare range, approach, fan power, sound, turndown, cell redundancy, and water-treatment assumptions. Ask the supplier for a selection sheet that repeats every design input and shows off-design operation.
What water-treatment evidence should a supplier provide?
Request the design water analysis, conductivity or cycles target, pH and hardness limits, filtration and blowdown arrangement, dosing points, drift-eliminator access, cleaning instructions, alarm set points, and restart procedure. The facility’s qualified water-management team should own the operating program and any Legionella risk controls; a tower quotation alone is not a health or compliance plan.
Can Domi supply a complete cooling tower?
Domi’s documented scope is custom coils and heat-exchanger components plus engineering and testing review. A complete cooling tower package, including tower casing, fan, fill, basin, controls, and water-treatment system, should be selected from a qualified tower OEM or system integrator. Send Domi a drawing and the component duty if you need a feasibility check for a coil or header inside a tower project.
Turn a cooling-tower concept into a reviewable RFQ
The fastest way to reduce rework is to define the heat-rejection boundary before comparing brands. Record the duty cases, wet bulb, range, approach, flow, circuit, fan arrangement, water program, service clearances, testing evidence, and component interfaces. Then ask each supplier to return the same set of values. If a coil or header is custom, route that drawing to a component specialist early so material, pressure, connection, and inspection decisions do not arrive after the tower has been purchased.
