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1 Evaporative cooler designs

Direct Evaporative Cooling (open circuit)

• used to lower the temperature of air by using latent heat of evaporation, changing water to vapor. In this process, the energy in the air does not change. Warm dry air is changed to cool moist air. Heat in the air is used to evaporate water.

Indirect Evaporative Cooling (closed circuit)

• similar to direct evaporative cooling, lowers the temperature of air by using latent heat of evaporation via some type of heat exchanger. The cooled moist air never comes in direct contact with products or environment.

1.1 Typical

Typically, residential and industrial swamp coolers use direct evaporative cooling and can be described as an enclosed, metal or plastic box with vented sides containing an axial fan (squirrel cage), fan motor with pulley wheels and a water pump to wet the cooling pads. They can be mounted on the roof (down draft) or exterior walls (side draft) of buildings. To cool, the fan draws ambient air through vents on the sides and through the damp pads. Heat in the air evaporates water from the pads which are constantly re-dampened to continue the cooling process. This cooled, moistened air is then delivered to the building via a vent in the roof or wall.

Because the cooling air originates outside the building, a vent must exist to allow air to move from inside to outside. Air should only be allowed to cycle once through the system or cooling efficiency will fail. This is due to the air reaching the saturation point.

1.1.1 Cooler pads

Traditionally, swamp cooler pads consist of aspen wood fiber inside a containment net, but more modern materials, such as some plastics and melamine paper, are entering use as cooler-pad media. Wood absorbs some of the water, which allows the wood fibers to cool passing air to a lower temperature than some synthetic materials. The thickness of the padding media plays a large part in cooling efficiency, allowing longer air contact. For example, an eight-inch-thick pad with its increased interface will be more efficient than a one-inch pad.

1.2 Cooling towers

Cooling towers are found on large commercial buildings, factories and power generation plants. The term "cooling tower" can be used to describe either an open or closed circuit system. There are three types of common cooling towers, natural draft which utilizes a tall chimney, fan assisted natural draft, and mechanical draft which uses power driven fan motors to force or draw air through the tower. If ambient conditions are right plumes (fog) can be seen rising out of cooling towers.

1.3 Misting systems

Misting system work by forcing water via a high pressure pump and tubing through a brass and stainless steel mist nozzle that has an orifice as size of about 5 micrometres producing a micro-fine mist. The water droplets that create the mist are so small, that it instantly flash evaporates. This flash evaporation can reduce the surrounding air as much as 35 °F in just seconds. For patio systems, it is ideal to mount the mist line approximately 8 to 10 feet above the ground for optimum cooling. Misting is used on for many different applications including orchids, pets, livestock, kennels, insect control, odor control, zoos, veterinary clinics, produce cooling, greenhouses, etc.

2 Performance

Understanding evaporative cooling performance requires an understanding of psychrometrics. Evaporative cooling performance is dynamic due to changes in external temperature and humidity level. An evaporative cooler will nearly always deliver air cooler than 80 ° Fahrenheit (27 ° Celsius).

Some rough examples clarify this relationship.

• At 90 °F (32 °C) and 15% relative humidity, air may be cooled to nearly 60 °F (16 °C).
• At 90 °F (32 °C) and 50% relative humidity, air may be cooled to about 75 °F (24 °C).
• At 105 °F (40 °C) and 15% relative humidity, air may be cooled to nearly 70 ° (21 °C).

Because swamp coolers perform best in dry conditions, they are prevalent and most effective in arid, desert regions like the southwestern USA and northern MexicoThis article is about the country Mexico. For other meanings, see Mexico (disambiguation The United Mexican States or Mexico ( Spanish: Estados Unidos Mexicanos or Mexico regarding the use of the variant spelling Mejico see section The name below) is a co.

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