What is a cooling tower?

A cooling tower is a specialised heat exchanger, found in many industries such as power plants, chemical processing, oil refining, steel mills, waste incineration and a whole range of manufacturing companies where process cooling is necessary.

Cooling towers utilise the natural process of evaporation to exchange the waste heat produced from industrial processes for cooler water that then gets reused over again. This is done by forcing air (often via a cooling fan) and water, to come into contact with each other.

In its simplest terms, a cooling tower follows these steps to exchange heat in water:

1. The warm water from the industrial processes, often air conditioning condensers, gets pumped into the cooling tower through pipes.
2. The water is then sprayed onto a heat exchange surface (fill) to maximise air-water contact.
3. The water is then exposed to air that is being pulled through the tower by an electric motor driven fan.
4. When the water and air meet a small amount of water evaporates, creating a cooling action.
5. The remaining cooled water collects in the tower basin where it then gets pumped back into the process equipment, repeating the loop, to use as much of the water as possible.

Cooling towers vary in size and design and are classified by the type of draft (natural or mechanical), and by the direction of air (counterflow or crossflow). However, all have the same primary function - to exchange heat - ideally, in the most effective way.

With not only laws in place to improve water efficiency, but the need to reduce costs and energy consumption also means that cooling towers need to be running as efficiently as possible.

Therefore, we have identified the 3 most common cooling tower problems, and how to fix them.

1. Corrosion

2. Scaling

3. Noise

What causes corrosion in cooling towers?

Over time, water will corrode just about anything. Combine that with unrelenting industrial chemicals, and corrosion becomes a very real concern for cooling towers.

Corrosion is caused by the combination and reaction of air, sodium, and other chemical components found in the water supply. This chemical reaction causes destruction or loss of the metal within the cooling tower.

Without placing preventative measures to reduce corrosion, it can threaten the safety and efficiency of the entire cooling process, in turn, increasing energy costs. If corrosion manages to progress even further it could cause damage or destruction to the equipment within the tower and lead to dangerous failures and costly repairs.

Luckily, there are several solutions to preventing or at least limiting corrosion in your cooling tower.

• Repair any damage already done
• Conduct proper and routine maintenance
• Regular inspection of the framework
• Solve any minor issues as they arise
• Prevent further corrosion and metal loss by using corrosion resistant materials where possible ie. polymeric coating solutions

What causes scaling in cooling towers?

Scaling is the thin coating of insoluble minerals or chemicals that break down during the heat exchange process and create layers on the cooling towers heat exchange surfaces.

Fundamentally, this scaling or build-up coats and insulates the heat exchange surfaces and prevents effective heat transfer.

Scaling must be removed or it will damage the piping and internal surfaces as well as reduce the overall efficiency of the cooling tower and increase operating costs and energy consumption.

You can prevent scaling in your cooling tower by:

• Using conductive tube coatings that allow the heat exchange to continue without providing a surface where the mineral build-up can stick
• Routinely monitoring and cleaning, to remove the scaling and prevent an accumulation of build-up
• Monitoring and treating the calcium levels in the water.

How can you reduce cooling tower noise emissions?

Cooling towers can produce high levels of noise pollution, which faces stringent noise regulations and laws. Therefore, companies have to abide by these rules and make sure the noise they produce is in accordance.

This can be hard for certain applications that produce huge out loads where sound reduction is imperative for example medical facilities, residential areas, and office buildings.

The primary sources of noise from cooling towers are the following:

• The fans, fan motors, and the airflow
• The droplets of the falling water hitting the basin (Waterfall noise)

1. Use premium efficiency cooling fans

With a proper aerodynamic design using optimised blade profiles and inserts, a new cooling fan would reduce the noise where it is generated, without reducing the efficiency of the fan.

Here at Howden we provide the next generation of ultra-low noise cooling fans - the SXT.
As cited in the EAA Euronoise 2018 conference the Howden SX series of fans are recognised as a primary noise reduction solution due to our unique design and ability to dramatically reduce noise level. Find out more - SX and SXT cooling fan

Download our - cooling fan brochure
 

2. Consider new drives or motors

Regulate the rotational speed of the fan with a variable-frequency drive, reduces sound and saves energy on down periods or low temperatures.
 

3. Implement noise reduction solutions

Reduce the impact noise of the water droplets caused when they fall into the basin by implementing noise reduction mats that float on the surface of the basin water. The flexible surface of the mats becomes the collision point for the droplets as opposed to the inflexible surface of the water meaning that the emitted sound energy would be decreased.
 

4. Optimise initial design

Carefully consider the initial design of your equipment to make sure everything is optimised for the size and energy required, preventing any excess power or speed being used, as they are both contributors to noise.

Prevent the propagation of sound by implementing absorbing silencers, create louvered air inlets, or build sound barrier walls. These are all options worth considering if it is not possible to modify or replace the noise sources or current technology.
 

So there you have it - by being aware of the common problems, which you can find in your cooling tower, you are more likely to successfully manage your heat exchange process. Ultimately, to reduce energy, improve efficiency, and save time and money.
 

If you require a copy of our latest Cooling Fans selection software - Howden Select, please register here. You will be sent an email with a link to the installation setup as soon as your profile has been activated. A quick start guide is included in the help menu for your convenience.

If you’re in need of industrial cooling tower maintenance - contact Howden today