Evaporative cooling use evaporation of water to produce significant cooling and saving energy. It is a very basic method of cooling air and the idea of evaporative cooling is handled with low cost for environmental control.

Evaporative cooling can be divided into Direct evaporative cooling and Indirect evaporative cooling. Results of both these methods are related to the wet bulb temperature located in the supply airstream. That is the reason why they are so popular in desert climates.

Direct Evaporative Cooling

Direct evaporative cooling can be applied to numerous applications where a low cost form of cooling is required to achieve a desired cooling effect.

This is simply where air is passed through a pad that is continually wetted either by mains water or a pumped system depending on application.  The sensible heat held within the airstream is required to evaporate the water on the media. This is similar to when you burn your hand, you will wet the surface then blow on it which causes a cooling effect. The downside to this system is that the airstream is now cooler but it has increased in humidity by absorbing the water vapour.

The amount of cooling that can be achieved by this method will depend on the conditions entering the wetted media (pads). In very humid conditions like the Far East, there is small benefit from installing such applications.  The humidity is already high and the air passing through the wetted pads will only absorb a small amount of water so the actual cooling effects will be negligible. If the conditions are hot and very dry, this system is perfect. The more moisture that can be absorbed into the air passing through the wetted pads, the greater the cooling effects will be.

This is a perfect solution when used for agriculture, both livestock and growing foodstuffs where the humidity is not a great issue and for large facilities where the ambient conditions are low in humidity.

Indirect Evaporative cooling

Very same principle as the above direct method but with a sensible wheel added to the combination.

This system uses two airflows, the one passing through the wetted pad is either an exhaust air from the building or a sacrificial air purely to achieve the cooling. After leaving the wetted pad this airflow now passes through a sensible wheel heat exchanger.

The supply air enters the sensible wheel where the cooling effect off the opposing airflow is now transferred. As the wheel has only sensible capabilities, there is no moisture transfer taking place.

The exhaust air stream is now warm and very humid and the supply airstream is cool.

Used in many applications where the humidity level is required not to rise.