How Evaporative Cooling Works

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 evaporative heat exchange is 90% less than air conditioning.

Services Requirement

An evaporative cooler requires mains water and 240v electricity supply.

Mechanics of the 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 pads.

The pads become saturated, air is drawn through 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. (see graph) 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 suffer from one in the summer. Humidistats can be fitted if humidity is critical
Read more details on humidity

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.

Why is it cheaper to run than Air Conditioning?

The economics of using evaporative cooling are surprising to most people. An 90% reduction in energy used compared to a conventional air conditioning 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 conditioning system when the temperature outside is 10°C ? In a modern, well insulated and air tight building with even a light occupancy the air conditioning is running almost continuously. By simply bringing in ambient air this will keep a building cool most of the year. By 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 in the UK