In terms of raw energy efficiency and the ability to provide precise cooling under fluctuating load conditions, recirculating evaporative cooling water systems with chillers or heat pumps are the most efficient way to remove heat from a process or building air. However, adiabatic cooling systems can be a good fit with an overall lower cost for heat removal in some climates and applications.
Cooling Media Pad
What are Adiabatic Cooling Systems?
Adiabatic cooling systems remove heat by evaporating water in a stream of warm, dry (low humidity) air. In the process of going from a liquid to a gas, the evaporated water simultaneously humidifies and cools the air stream to within a few degrees of the wet bulb temperature.
Cooling systems that employ adiabatic cooling can have a wide variety of names and configurations, but will generally fall into one of three categories:
Adiabatic Cooling Tower Illustration
Where are Adiabatic Cooling Systems a Good Fit?
Adiabatic cooling systems can be a good technical and economic fit in hot, dry climates, especially where water supplies are scarce and costs are high. They can also be a good match where outside air temperatures are cool enough for most of the year for air-cooled fluid coolers or refrigerant condensers to operate efficiently.
The data center industry has employed adiabatic cooling technology on the air side for air handlers for years. With the development of new adiabatic designs applied to fluid coolers and refrigerant condensers and the increasing scarcity of water, adiabatic cooling systems are seeing wider use across a range of industries and applications.
Water Treatment Requirements
There may be two separate water systems in an adiabatic cooling tower: a water system for humidifying and cooling the inlet air stream and a recirculating closed loop.
Eliminating the recirculating cooling tower from the cooling equation greatly simplifies water treatment. The closed loop portion of an adiabatic system should be treated with corrosion inhibitors appropriate for the water quality and system metallurgy. Don’t forget that glycol may be required for freeze protection in cold climates.
To create a high surface area for the water to cool quickly and totally evaporate in the air stream, adiabatic cooling systems typically use wetted humidification pads or misting spray nozzles. If the makeup water to the cooling pads or spray nozzles has significant hardness, softening may be necessary to help prevent the build-up of mineral deposits that will reduce cooling efficiency. Cooling media pads should be maintained and replaced according to the manufacturer’s specifications. Where misting spray nozzles are used, deionized water may be specified if adiabatic cooling will be employed more than a certain number of hours annually.
Adiabatic designs that employ a sump or basin to recirculate the spray water may also require bleed control equipment, a scale/corrosion inhibitor, and biocide additions. Although adiabatic cooling system designs may be less prone to Legionella amplification and transmission than a standard cooling tower systems, the spray water system can generate aerosols that present Legionella concerns. All water treatment chemicals should conform to manufacturer specifications and regulatory requirements.
In many geographies and applications, adiabatic cooling systems can be a good fit. Although routine preventative maintenance is required for the cooling pads or spray system, the overall water treatment requirements are greatly reduced.
For more information on treating adiabatic cooling systems or for help determining if your facility is a good fit, contact Chem-Aqua today!
Written by: Matt Schnepf and Allan Browning