Evaporative Cooling Performance

Air and Water
Theoretical Performance
Actual Performance
 

Air and Water

Air acts like a sponge to water. Just as spoe is limited in the amount of water it can absorb air is also limited. A key difference is the hotter the air the more water it can support before it becomes ‘saturated’ and can hold no more water. It can be seen from the data below that this amount of water dramatically increases as the temperature increases.

The maximum amount of water supported by air at atmospheric pressure is:

The term relative humidity refers to the actual amount of water in the air compared with its maximum or saturated value, and is stated as a percentage.

e.g. Water at 30°C with 17g of water in it is 50% RH

Many engineers use a Psychrometric chart to understand the relationship between air and water. This chart is explained in detail section 17

Theoretical Performance

 The performance of an evaporative cooler is dependent upon both the temperature and the relative humidity of the air passing over the pads together with the efficiency of the pads. The theoretical cooling is shown below.

Actual Performance

The graph below shows an actual example of performance of a cooler.