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How Evaporative Cooling Works

An overview and summary

Principle of Evaporative Cooling

Cooling is provide by Evaporative heat exchange which takes advantage of the principles of the latent heat of evaporation where tremendous heat is exchanged when water evaporates. It makes use of the free latent energy in the atmosphere. Compared to air-conditioning which uses mechanical refrigeration, the operating cost of heat evaporative exchanging are 90% less than air conditioning.
Mechanics of Unit
Water is brought into the cooler from the mains water supply and is pumped up to the top of the unit using a circulation pump. The water is then dispersed over the Celdek pads using a water distribution system which allows the water to flow continually over the pad. The pads become saturated, air is drawn through the pads and the water evaporates causing the air to cool. The cool air is then ducted round the building to provide cooling by means of an axial fan.
Temperatures Achievable
The hotter the outside temperature and the lower the humidity, the greater will be the cooling effect. On the hottest day in the UK up to 15°C of cooling can be achieved through this process. The air off temperature of an EcoCooler in the UK is always below 23°C, thus providing excellent comfort cooling for most building requirements.
Humidity
With an evaporative cooler you are basically turning a hot summer day into an April day. If the building does not suffer from a humidity problem in April it will not in the summer. Humidistats can be fitted if humidity is critical.
evaporative cooling explained
In the UK during a typical hot period the ambient temperature approaches 30°C. This coincides with a Relative Humidity of under 50%. As the air passes over the pads it will typically cool down to about 22°C. There is less cooling in the night as the temperatures reduce and the humidity rises.
evaporative cooling performance table
The graph above shows the performance of a cooling unit in the UK. In cool conditions the EcoCooler operates in ventilation mode and in hot conditions in cooling mode. A sophisticated control system which comes as standard can automatically set the fan speed to constantly minimise the electricity use of the fan.

When to use Evaporative
Cooling?

Ventilation systems can provide comfort cooling for most of the year. During prolonged periods of high temperatures they are unable to maintain internal temperatures below 25°C. It is at this point that evaporative cooling is brought in. Using Evaporative cooling as an integral part of a balanced ventilation system means that the temperature of a building can be controlled even on the very hottest days.

evaporative cooler
Why is it cheaper than
Air Conditioning?

The economics of using evaporative cooling are surprising to people. An 85% reduction in energy used compared to a air con unit seems too good to be true. This is achieved because in the UK it is cold most of the time! Why do we need to run an air con system when there is an ambient temperature of 10C? In a well insulated & air tight building with even a light occupancy the air con is running almost continuously. By simply bringing in ambient air this will keep a building cool most of the year. Using a control system to minimise energy usage of fans coupled with evaporative cooling, relatively low flow rates of air are required. The only significant energy use is in the fan for the air movement. Typically a 1KW evaporative cooling system can manage a 20KW load.

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