An introduction to cooling towers

An introduction to Cooling Towers

Find out how a cooling tower is designed to cool large quantities of water that circulate in a cooling system and learn about the different types of cooling towers.

Cooling is the focal point of many industrial processes. And one way of ensuring optimal cooling is by means of cooling towers, which can be found in the majority of installations in industrial buildings.

In this module, we’re going to give you a thorough introduction to cooling towers. To put it in simple terms, a cooling tower is a device designed to cool large quantities of water that circulate in a cooling system. Its main purpose is to transfer heat from the cooling water to the air by evaporation. But how does a cooling tower work in practice? Let’s take a closer look.

In a cooling system with a cooling tower, hot water from sources such as machines or process cooling flows through the pipes to a cooling tower. "As the water enters the cooling tower, it is sprayed out of a number of nozzles. The water is sprayed over a packaging – also known as a fill. 

The main purpose of the fill is to spread the water over a larger surface, ensuring a larger evaporating surface."

As the water runs down the sides of the fill, and as the air flows the opposite way, some of the water evaporates into air. The air absorbs the heat created by this evaporation, thus lowering the temperature of the remaining water.

The remaining water, which is now cooled, drips down to a basin at the bottom of the cooling tower, where it is recirculated into the system. 

The air, on the other hand, is sucked upwards by the fan. Before it makes its way out of the cooling tower, it passes through drift eliminators.

The air – which is highly condensed – travels at a high velocity, hitting the zig-zag-shaped drift eliminators several times before exiting the fan.

The condensation that appears on the drift eliminators drips back through the cooling tower and joins the remaining water at the bottom. 

Generally speaking, less than 30% is lost to evaporation, drip loss, leakage and discharge into a blowdown system. By using the right control, however, you can save 20% of the 30% lost to evaporation.

So, if, for instance, 100 litres of water are lost to evaporation every hour, the right control will allow you to save 20 litres an hour.

Another advantage is safety. Cooling towers use no dangerous chemicals during the cooling process, making it much safer for you to work with.

So, now that we’ve covered the basics of cooling towers, let’s take a look at the different types of typical cooling tower systems. 

From an industrial perspective, there are generally two main types of cooling towers: forced draft counter flow cooling towers, and forced draft cross flow cooling towers.

In forced draft counter cooling towers, the air is pulled up through the tower by means of fans, and the water moves from the top and down through the tower.

In a forced draft cross flow cooling tower, the air is pushed across the fill and then up through the cooling tower. Just like the forced draft counter cooling tower, water is moved downward from the top.

So, that covers our basic introduction to cooling towers. In the next module, we will dive much deeper into cooling towers and show you how to energy-optimise them.