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Portable evaporative air coolers
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You are here:- home > cooling index > evaporative cooling homepage > what is evaporative cooling?

What is evaporative air cooling?

Evaporative air cooling is a naturally occurring phenomenon. When air and water come into contact the water evaporates into the surrounding air, reducing its temperature. This is why on a hot day it is cooler near a lake, waterfall or fountain.

The cooling sensation felt by a person when a breeze passes over and evaporates perspiration on their skin, is the most common human experience of the phenomenon.

Evaporative air cooling is the oldest known method of cooling. The ancient Egyptians used it to reduce the temperature inside their buildings. They placed water saturated cloth sacks in windows and doors, as warm air entered, it passed through the sacks and was cooled.

How do evaporative air coolers work?

In the Waycool portable evaporative air coolers, a pump circulates water from a reservoir tank and sprays it onto absorbent cooling pads in the sides of the cooler.

A fan draws warm air from outside through the wet pads, as it passes through the pads it is cooled by evaporation. 

This cooled air is then blown out through the nozzle on the top of the cooler and circulated around the building.

portable evaporative air cooler
 

In the case of our evaporative fans. The impellors have small holes in them, which release very small particles of water into the air stream, where they instantly evaporate (called flash evaporation) cooling the air stream.

evaporative fan

How effective is evaporative air cooling?

Evaporative air cooling is a very effective way to cool air when the humidity is low. However, its effectiveness is reduced as humidity levels rise, and eventually when the air is fully saturated the cooling effect stops altogether.

Fortunately as the temperature rises, the humidity drops. So at the hottest time of day evaporative cooling is at its most effective!

The following chart shows evaporative air coolers are capable of delivering comfortable air conditioning over a wide range of temperature and humidity levels.

Evaporative cooler outlet temperatures
Ambient
Temperature C
Relative humidity %
 
10
20
30
40
50
60
70
80
90
10
4.0
4.5
5.5
6.0
7.0
7.5
8.0
9.0
9.5
15
7.5
8.5
9.5
10.5
11.0
12.0
13.0
13.5
14.0
20
11.0
12.0
13.0
14.5
15.5
16.5
17.5
18.5
19.0
25
14.5
16.0
17.0
18.5
20.0
21.0
22.0
23.0
24.0
30
17.5
19.5
21.0
22.5
24.0
25.0
26.5
28.0
29.0
35
20
23.0
25.0
26.5
28.5
30.0
31.5
32.5
34.0
40
23
26.5
29.0
31.0
32.5
34.5
 
 
  
45
26
29
32.5
35.0
 
 
 
 
 
50
29
32.5
36.5
 
 
 
 
 
 

Example: - At an ambient temperature of 35C and a relative humidity of 30% the air from the cooler will be 25C, a 10C drop

In addition to cooling the air, evaporative air coolers have the additional benefit that just like ceiling fans, they produce a cooling breeze, so occupants will feel several degrees cooler than the temperatures on the chart.

The future of evaporative air cooling

Evaporative air cooling is now one of the fastest developing areas of the HVAC market.

According to a report by the World Bank there are over 4 million evaporative air coolers in operation in the United States of America, providing estimated annual energy savings equivalent to 12 million barrels of oil, in addition to an annual reduction of 5.4 billion pounds of CO2 emissions.

As the effects of global warming, are felt in cooler climates, the use of evaporative air coolers is becoming widespread, especially in the United Kingdom and Europe.


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