Evaporative cooling walls for dry-coolers and chillers. Freecooling

Price for 1 m ²

Evaporative cooling
Physics teaches us that water, when water evaporates in adiabatic cooling systems, removes a large amount of energy. The temperature thus drops to almost the dew point (depending on efficiency). For the water to evaporate, energy is needed, namely 2501 kJ for every kilogram of evaporated water. Liquid water takes the energy needed to evaporate from the environment, mostly air, and consequently the air is cooled. In simplified terms, it can be stated that sensible heat (temperature) is converted into latent heat (relative humidity). As a result, we get cooled and moistened air. Such cooling is called evaporative cooling, evaporative cooling, or adiabatic cooling.

Fig. 1 Evaporative cooling presented in the Mollier diagram [source: own]

Heat exchangers (dry-coolers and chillers) adiabatically cooled The
amount of heat emitted by air conditioning systems using dry-choolers and chillers depends on various factors, including the temperature (dry thermometer) of the air. In climates where the average relative humidity in summer is less than about 50%, evaporative cooling can be used.
Most chiller and dry-cooler installations are designed to operate efficiently during summer high temperatures, which leads to significant equipment oversizing. Oversizing dry coolers and chillers means: increased installation cost, increased operating costs, greater environmental pollution, greater noise and increased auxiliary costs (e.g. reinforced ceiling structure for a heavier unit). Thanks to water cooling walls, the investment and operating costs can be significantly reduced by lowering the temperature of the air passing through the heat exchangers of dry-coolers and chillers.

Fig. 2 Water cooling walls mounted on a drycooler [source: own]

Water is pumped to the evaporation panels from the water tank under a slight pressure. The water is then evenly distributed over the cellulose inserts so that the entire evaporation panels are saturated with water. The air flowing through the cellulose cartridges is cooled, but there is no drip formation or water entrainment from the cartridges. As a result, the exchanger does not come into direct contact with water and there is no precipitation of scale on the heat exchanger fins.

Advantages of using evaporation panels for dry-coolers and chillers:
- Lower installation costs, lower operating costs, less environmental pollution, less noise
- Heat exchanger protected from sunlight
- Heat exchanger protected against external pollution
- Lower condensation pressure and pressure on the compressor increasing service life compressors and system
- Reduced failure rate of dry-cooler and chiller systems, especially in summer
- Cooling capacity by at least 20-30% higher
- Easy installation
- No water treatment required
- Reduced environmental impact: lower electricity consumption
- Air temperature cooled by 5 10ºC

Example of application in a chiller
The table below shows the data in which we assume constant air flow of chiller fans.

To sum up
We know from scientific research and our own experience that using evaporation panels are non-invasive in relation to cooling devices and thanks to the use of evaporative cooling in chillers and dry-coolers, it is possible to significantly increase the efficiency and achieve significant operating savings. Usually, less than one cooling season is needed to pay for investment in evaporation panels.