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How Do Evaporative Air Cooling Work?

Last updated Dec. 13, 2019

Evaporative air coolers are mostly known for being cost-effective alternatives to air conditioners.

They consume very little energy when compared to air conditioners but are quite effective in cooling the air and bringing much-needed comfort during summer.

While energy-efficiency is very important, it is not the most remarkable thing about air coolers.

If you care about the environment or are interested in the way things work, the most remarkable thing about air coolers will be the way they work.

Working on the principle of evaporative air cooling, air coolers are eco-friendly machines that use just air and water to achieve cooling.

How do they achieve this?

This is what we will try to discuss as briefly as possible here.

How Do Evaporative Air Cooling Work?

To understand how it works, we have to understand what evaporative air cooling means.

Simply put, evaporative air cooling is the natural process of air cooling through the evaporation of water.

It is a completely natural process that works because water has a large enthalpy of vaporization, which means it will need to absorb a large amount of heat to evaporate.

Evaporative air cooling happens even without human intervention.

When we sweat during sunny days, we feel cooler when the sweat evaporates from the surface of our body:

this is evaporative cooling at work. It is the same process at work in lakes and other natural water bodies.

When air blows through these natural bodies of water, it becomes cooler as it reaches the shores.


Air Coolers and Evaporative Air Cooling

As stated already, evaporative air cooling is a natural principle that can happen even without human intervention.

The air cooler, which is also referred to as evaporative air cooler, is just a machine that facilitates this process and brings about a significant drop in temperature that can improve comfort levels for humans.

Before the invention of the air cooler, the evaporative cooling principle was tapped into by people of an ancient civilization.

There are records that slaves in Egypt fanned jars of water to cool rooms as far back as 2500 BC.

Some civilizations used porous earthenware vessels and some other sorts of inventions that utilized the natural evaporative cooling principle to cool the air and improve comfort.

What we have today as evaporative coolers are just modernized forms of what they had then.

The fundamental principle of operation is unchanged though there are minor changes in the methods of operation and electricity and technology has automated the process for us today.


So How Do Evaporative Air Cooling Work?

If you have followed closely, you will understand fully what evaporative cooling entails.

How then does it work, especially with the air cooler in use?

We will discuss how this happens in stages but before that, we will briefly look at heat and the role it plays in the process.


Heat is a form of energy.

Technically, it is the flow due to the difference in temperature between two objects.

It is the driving force in the evaporative cooling process and happens as a result of a difference between the temperature of the air that is being drawn into the air cooler and the temperature of the moist pads in the machine that serves as the cooling surfaces.

Heat exists in two forms: sensible heat (that can be sensed or felt) and latent heat (hidden heat that cannot even be detected by a thermometer).

The heat at work in evaporative cooling is referred to as the 'Latent Heat of Evaporation'.

It is the heat absorbed by water on the cooling pads as it changes from liquid state into vapour.

The amount of energy/heat absorbed by the changed water is contained in the molecular structure of the vapour without any change of temperature in the water.

The loss of energy in from the surrounding air, however, results to decrease in its temperature.


How Evaporative Air Cooling Works an Air Cooler

To bring about a decrease in ambient temperature, the air cooler employs evaporative cooling.

The machine normally has a constant supply of water that keeps the pads adequately wet so that they can efficiently serve as the cooling surfaces.

The entire process is in the following stages:

1. An Air Cooler Absorbs Warm Air from the Environment

The air cooler is designed in a manner that the fan and cooling pads can work together to suck up warm air from the environment.

The pump system ensures that the pads, which are normally located at the back and sides of the machines are always wet and ready to absorb warm dry air.

The warmer and drier the air, the better.

2. The Warm Air is Passed through the Cooling Pads

The warm air that is entering the air cooler is directly passed through the wet pads.

These pads which are called cooling pads serve as the cooling surfaces for the air and are vital for the evaporative cooling process.

3. The Heat from the Warm Air Cause Evaporation of Water

As the warm hot air is passed through the cooling pads, some of its heat energy is used up to cause evaporation of water from the surface of the pads.

As stated earlier, water absorbs a large amount of heat to change from liquid state to vapour.

This means that the warm air will lose a lot of its heat energy, resulting in relatively cool air.

Some amount of moisture resulting from the evaporation is also added to the air.

4. The Cool and Moist Air is Pumped into the Areas that Need Cooling

The result of the process described above is air that is much cooler and moister than the one that was sucked into the air cooler.

This air is pumped into the area that needs cooling by the fan system of the air cooler.

This means that the air coming out from the air cooler is cool, moist, and feel comfortable.

5. The Entire Process is Repeated

The process described above is repeated continuously as long as there is adequate water supply to the cooling pads and constant electric power supply to the entire unit.

Ventilation is also important since constant air exchange is relevant for the continuity of the process.

Evaporative air cooling works by using the heat energy in warm air to cause evaporation of water from a cooling surface, producing cooler and moister air.

With the air cooler, the process is driven by electricity that powers the entire unit to keep the pads constantly cool, suck in warm air from the environment, and blow the cool moist air that results from the process into the area that needs cooling.

Once the conditions are right, the process will continue seamlessly and keep your residential or commercial space cool and comfortable.

If you have any further questions, contact us and we would be pleased to help you.