Cooling is provided 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 can be up to 80% less than air conditioning, however these systems do use water, so although they are cheaper to run in electrical terms they also use water were the standard air conditioning systems do not use any water.
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 or kitchen.
The hotter the outside temperature and the lower the humidity, the greater will be the cooling effect. On the hottest dry days in the Australia up to 15°C of cooling can be achieved through this process, however as the relative humidity increases the temperature difference decreases. This is why in Newcastle these type of systems are mainly used as fresh air make up for commercial kitchens as a cheap means of getting some tempered air into the hot kitchen. When we start to get further into the hunter valley and into the West were they experience dry heat, these type of systems start to get good temperature differences from outside ambient air to the tempered air drawn through the evaporative cooler and supplied into the building.
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.
Most designs take advantage of the fact that water has one of the highest known enthalpy of vaporization (latent heat of vaporization) values of any common substance. Because of this evaporative coolers use only a fraction of the energy of vapour-compression or absorption air conditioning systems. Unfortunately, except in very dry climates, the single-stage (direct) cooler can increase relative humidity to a level that makes occupants uncomfortable. Indirect and Two-stage evaporative coolers keep the RH lower.
Indirect evaporative cooling (closed circuit) is similar to direct evaporative cooling but uses some type of heat exchanger. The cooled moist air never comes in direct contact with the conditioned air. The moist air stream is released outside or used to cool other external devices such as solar cells which are more efficient if kept cool.
One indirect cooler manufacturer uses the so-called Maisotsenko cycle which employs an iterative (multi-step) heat exchanger that can reduce the temperature to below the wet-bulb temperature. While no moisture is added to the incoming air the RH does rise a little according to the Temperature-RH formula.
Conditioned air without added moisture increases the evaporation of perspiration improving the cooling effect of Indirect compared to Direct.
In the first stage of a two-stage cooler (or indirect-direct cooling), warm air is pre-cooled indirectly without adding humidity (by passing inside a heat exchanger that is cooled by evaporation on the outside). In the direct stage, the pre-cooled air passes through a water-soaked pad and picks up humidity as it cools. Since the air supply is pre-cooled in the first stage, less humidity is transferred in the direct stage, to reach the desired cooling temperatures. The result, according to manufacturers, is cooler air with a relative humidity between 50-70%, depending on the climate, compared to a traditional system that produces about 70–80% relative humidity in the conditioned air.
Over the past 73+ years Coles Refrigeration and Air-Conditioning have maintained their reputation as Newcastle’s leading air-conditioning and refrigeration company by ensuring their staff have the products, knowledge, expertise and experience to create efficient and reliable air-conditioning systems tailored to your specific requirements.
Contacting Coles refrigeration and Air-conditioning to organise a consultation with a sales engineer will ensure your system is able to meet all of your requirements in the most practical and efficient way. This process is obligation free, free of charge and will provide you with not only a detailed quote but also honest valuable advice from recognised air-conditioning experts with decades of experience.
“Your professionalism, quality, honesty, and delivery timeframes were outstanding given you were under an extremely tight schedule to get the project completed. I was especially impressed with your effort to accommodate any additions to the original scope, including the client's request to refurbish the entire kitchen two weeks prior to Christmas. I have no hesitation in recommending you and Coles Refrigeration & Air Conditioning to future clients and trust we will continue to further strengthen the relationship between our companies.”
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“Throughout all the stages of development and construction, I always found the staff from Coles to be highly professional and diligent in their works. Cole's tradesmen who carried out the works at our site were always helpful and met our stringent OH&S requirements. The buildings that were refurbished present various challenges with timeframes and meeting relevant codes and standards. With Cole's help, we were able to meet and exceed all expectations. I have no hesitation in recommending Coles Refrigeration for any future works in which they tender.”
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