How Evaporative Cooling Works

As warm air passes over wet filter pads water naturally evaporates into the air. The air is cooled as it gives up the heat required to evaporate the water.

evaporation process

An AFCOOL has CELdek pads, made by Munters, which are kept saturated with water when in ‘Cool’ Mode. Water from the sump is pumped over the pads via a water distribution system.

cooler diagram

An axial fan draws the air through the pads and then into the air distribution system.

CELdek pads

The CELdek pads, manufactured by Munters, are cellulose based. A removable insect screen is incorporated into the side panel to protect the pad and provide basic hygiene.

AFCOOL Performance

The performance of an AFCOOL is dependent upon the temperature of the air and its relative humidity (RH). Higher temperatures give greater cooling. Low RH gives greater cooling.

Relative Humidity
Temp	20%	30%	40%	50%	60%	70%	80%
20°C	10.2	11.6	13.1	14.3	15.6	16.8	17.9
25°C	13.7	15.4	17.0	18.6	20.0	21.3	22.6
30°C	17.0	19.1	21.0	22.8	24.4	26.0	27.4
35°C	20.4	22.9	25.1	27.1	29.0	30.6	32.1

In a temperate climate, such as the UK, hot weather coincides with low RH. Detailed information about local weather can be found on www.wunderground.com.

The diagram below shows the typical profile for temperature and humidity on a very hot day in the UK. It is very rare for the cooled air temperature to exceed 22oC.

It can be seen that the RH is low when the temperature is high. This means that the maximum cooling effect occurs at the highest temperatures.

In April and October we often see days with the air at 20°C and RH over 90%. An AFCOOL takes August weather conditions and transforms them into April conditions.

In cool conditions the AFCOOL operates in ventilation mode and in hot conditions operates in cooling mode. A control system can automatically set the fan speed to constantly minimise the electricity use of the fan.

Evaporative Cooling Brochure 2007