It is also known as Swamp cooler or Desert cooler. These types of coolers work on the principle of enthalpy of evaporation. In this process heat in the air is transferred to the liquid to turn it into vapors, hence giving it the name “evaporative air cooler”. This way of cooling is very different from the systems of cooling through vapor compression or refrigeration through absorption. This technique is not new to the humanity, the ancient Persian and Egyptian Civilizations also used to cool air down through the same principle but in a different way. They had only a single air inlet for a house and an exhaust chimney. The air coming from the inlet is directed to the underground water “kanat” (kanat was a long water containing tank) which cooled down air and that air is then released to the building while the hot air is exhausted through the chimney at the roof. Today’s evaporative air cooler is better in design but same in the process. There are two methods nowadays to cool air down by evaporation:
- Direct Method
- Indirect method
Direct Method Cool Air Down By Evaporation
In this method, latent evaporation heat is used to decrease the temperature of air but it also causes the liquid water to convert into water vapors thus increasing the humidity level in the air. The energy of air doesn’t increase or decrease in the process. The high-temperature air from outside becomes cool but humidity level in the air increases due to the moisture it catches. Liquid water is converted into vapors by using the hot air coming from outside. The humidity level rises higher than 80% due to which people in the environment start sweating. To stop this effect on human body air is continuously exhausted out.
In modern day machines, the air is passed through the wet cooling pads which provide the larger contact of air with water so that water vapors more quickly. The fan is also used to increase the air flow speed. There is a water shower at the top of the pad which showers the water continuously and keeps the pads wet. Water drips down till the bottom and the pump circulates the dripped water again to the shower at the top.
This circle continues and cooled air is blown out by a fan in one direction, providing the cooling source. This continuous circulation of water in Pads causes scaling of the water minerals on the pads mostly salt, this process slowly reduces the efficiency of the evaporative air cooler, completely blocking the air at the end, this may take some time more or less depending on the material of Pads.
Indirect Method Cool Air Down By Evaporation
This Method is the enhanced form of the direct cooling method. In addition to the direct cooling method, this process also uses the heat exchanger to cool down the air by transferring cool energy to it. The cool air from the direct cooling process goes through a coil and the air for supply is passed through the coil, by this method supply air is cooled down without having contact with water vapors. By this way, air is cooled without being moist thus keeping the humidity level controlled.
This method is more efficient in cooling than the direct method but by this method water is circulated more than in the direct method which increases the overall water consumption. It also causes the scaling process to be faster, requiring more maintenance. These machines with indirect cooling methods are used very less often as compared to the direct one due to the higher water consumption and operational costs.
Uses Of Evaporative air Cooler
Since the early ages, this method is being used to cool down air. The job of the fan was done by a slave who used a fan to blow the water container by hand to cool down the building.
Now a day this evaporative air cooler (also known as “Swamp cooler” or “Desert cooler”) is widely used as a cheap cooling option and is also very popular as “Desert cooler” due to its usability in the dry climate of a desert. Evaporating cooling works by cooling down the air by increasing the moisture in it which is good for desert areas, as it is beneficial to human body and fulfills body’s humidity requirements.
But it cannot work efficiently in humid areas like river banks or sea shores where the humidity level is already high. Because it works by moisturizing the dry air to cool it down, it doesn’t work where the air is already moist, this limits its work area to the places with the dry climate like the desert.
This is very suitable if most of the Middle-east as it comprises most of the desert area.
The leading companies in this industry have made their own models of evaporative air coolers and sell them in the market with their own names, for example Windmason.