Evaporative coolers (also called swamp, desert, or air coolers) are devices that cool air through the simple evaporation of water. Evaporation is the process by which Molecules in a Liquid state (e They differ from refrigeration or absorption air conditioning, which use the vapor-compression or absorption refrigeration cycles. Refrigeration is the process of removing Heat from an enclosed space or from a substance and moving it to a place where it is unobjectionable The absorption refrigerator is a Refrigerator that utilizes a heat source (e The term air conditioning refers to the cooling and dehumidification of indoor air for Thermal comfort. Vapor-compression refrigeration is one of the many Refrigeration cycles available for use In the United States, small-scale evaporative coolers are called swamp coolers by some users due to the humid air conditions produced. The United States of America —commonly referred to as the The name sump cooler is also used. Air washers and wet cooling towers utilize the same principles as evaporative coolers, but are optimized for purposes other than air cooling.

Evaporative cooling is especially well suited for climates where the air is hot and humidity is low. Evaporative coolers (also called swamp, desert, or air coolers) are devices that cool air through the simple Evaporation of water Climate encompasses the temperatures humidity rainfall atmospheric particle count and numerous other meteorogical factors in a given region over long periods of Humidity is the amount of water vapor in the air In daily language the term "humidity" is normally taken to mean Relative humidity. For example, in the United States, the western/mountain states are good locations, with swamp coolers very prevalent in cities like Denver, Salt Lake City, Albuquerque, El Paso and Phoenix, where sufficient water is available. The United States of America —commonly referred to as the The City and County of Denver (pronounced /ˈdɛnvɚ/ is the Capital and the most populous city of Colorado, in the United States Salt Lake City is the Capital and the most populous city of the U Phoenix (ˈfiːˌnɪks O'odham Skikik, Yavapai Wasinka, Western Apache Fiinigis, Navajo Hoozdo, Evaporative air conditioning is also popular and well suited to the southern (temperate) part of Australia. For a topic outline on this subject see List of basic Australia topics. In dry climates, the installation and operating cost of an evaporative cooler can be much lower than refrigerative air conditioning, often by 80% or so. But evaporative cooling and vapor-compression air conditioning are sometimes used in combination to yield optimal performance. Some evaporative coolers may also serve as humidifiers in the heating season. A humidifier is a household Appliance that increases Humidity (moisture in a single room or in the entire home

In moderate humidity locations there are many cost-effective uses for evaporative cooling, in addition to their widespread use in dry climates. For example, industrial plants, commercial kitchens, laundries, dry cleaners, greenhouses, spot cooling (loading docks, warehouses, factories, construction sites, athletic events, workshops, garages, and kennels) and confinement farming (poultry ranches, hog, and dairy) all often employ evaporative cooling. Large institutions that require a constant flow of clean linen working- Clothing or Uniform, will often employ the services of an industrial laundry Dry cleaning is any cleaning process for Clothing and Textiles using an organic Solvent rather than Water. A greenhouse (also called a glasshouse or hothouse) is a building where plants are cultivated In highly humid climates, evaporative cooling may have little thermal comfort benefit beyond the increased ventilation and air movement it provides. Human thermal comfort is defined by ASHRAE as the state of mind that expresses satisfaction with the surrounding environment (ASHRAE Standard 55

Contents 1 History 2 Evaporative cooling 3 Evaporative cooler designs 3.1 Typical 3.1.1 Cooler pads 3.2 Evaporative (wet) cooling towers 3.3 Misting systems 3.3.1 Misting fans 4 Performance 5 Comparison to air conditioning 5.1 Advantages 5.2 Disadvantages 6 Health Concerns 7 See also 8 References 9 External links

History

Civilizations throughout the ages have found ingenious ways to combat the heat in their region. An earlier form of air cooling, the windcatcher (Bâd gir), was invented in Persia (Iran) thousands of years ago in the form of wind shafts on the roof, which caught the wind and passed it through water and blew the cooled air into the building. A windcatcher ( Persian: بادگیر Bâdgir, Arabic: بارجيل Baarjiil) is a traditional Persian architectural device The Persian Empire was a series of Iranian empires that ruled over the Iranian plateau, the original Persian homeland and beyond in Western Asia For a topic outline on this subject see List of basic Iran topics. ^[1] Nowadays Iranians have changed the windcatcher into an evaporative cooler (Coolere Âbi) and use it widely. A windcatcher ( Persian: بادگیر Bâdgir, Arabic: بارجيل Baarjiil) is a traditional Persian architectural device There are 9,000,000 evaporative coolers in central Iran, and in just the first two months of year 1385 in the (Persian/Iranian calender) (April–May 2006) 130,000 evaporative coolers were sold in Iran. The Iranian calendar or Solar Hejri (تقویم هجری شمسی؛ سالنمای هجری خورشیدی Taqwim Hejri Shamsi Salanmay Hejri Khurshidi) is an astronomical

Evaporative cooling was in vogue for aircraft designs for some time in the late 1930s. In this case the system was used in order to reduce, or eliminate completely, the radiator which would otherwise create considerable drag. Radiators and convectors are types of Heat exchangers designed to transfer Thermal energy from one medium to another for the purpose of cooling In these systems the water in the engine was kept under pressure with pumps, allowing it to heat to temperatures above 100 Celsius, as the actual boiling point is a function of the pressure. The super-heated water was then sprayed though a nozzle into an open tube, where it rapidly boiled and released its heat. The tubes could be placed under the skin of the aircraft, resulting in a zero-drag cooling system.

However these systems also had serious disadvantages. Since the amount of tubing needed to cool the water was large, the cooling system covered a significant portion of the plane even though it was hidden. This led to all sorts of added complexity and the systems were always terribly unreliable. In addition this large size meant it was very easy for it to be hit by enemy fire, and practically impossible to armor. British and US attempts to use the system turned to ethylene glycol instead. Ethylene glycol ( monoethylene glycol ( MEG) 12-ethanediol, IUPAC name: ethane-12-diol) is an Alcohol with two -OH The Germans instead used streamlining and positioning of traditional radiators. Even its most ardent supporters, Heinkel's Günter brothers, eventually gave up on it in 1940. Heinkel Flugzeugwerke was a German aircraft manufacturing company founded by and named after Ernst Heinkel. Siegfried and Walter Günter were twin brothers and aircraft designers born 8 December 1899.

Evaporative cooling was used in some automobiles, often as aftermarket accessories, until modern vapor-compression air-conditioning became widely available.

Evaporative cooling

Evaporative cooling is a physical phenomenon in which evaporation of a liquid, typically into surrounding air, cools an object or a liquid in contact with it. Evaporation is the process by which Molecules in a Liquid state (e Latent heat describes the amount of heat that is needed to evaporate the liquid; this heat comes from the liquid itself and the surrounding gas and surfaces. In Thermochemistry, latent heat is the amount of Energy in the form of Heat released or absorbed by a substance during a change of phase When considering water evaporating into air, the wet-bulb temperature, as compared to the air's dry-bulb temperature, is a measure of the potential for evaporative cooling. The wet-bulb temperature is a type of Temperature measurement that reflects the physical properties of a system with a mixture of a Gas and a The dry-bulb temperature is the Temperature of Air measured by a Thermometer freely exposed to the air but shielded from Radiation and Moisture The greater the difference between the two temperatures, the greater the evaporative cooling effect. When the temperatures are the same, no net evaporation of water in air occurs, thus there is no cooling effect.

The simplest example would be perspiration, or sweat, which the body secretes in order to cool itself. The amount of heat transfer depends on the evaporation rate, which in turn depends on the humidity of the air and its temperature, which is why one sweats more on hot, humid days. Humidity is the amount of water vapor in the air In daily language the term "humidity" is normally taken to mean Relative humidity.

Another, recent application of evaporative cooling is the "self-refrigerating" beverage can. [1] A separate compartment inside the can contains a desiccant and cooling liquid. A Desiccant is a Hygroscopic substance that induces or sustains a state of dryness ( Desiccation) in its local vicinity in a moderately-well sealed container Just before consumption, the desiccant comes into contact with the cooling liquid, inducing evaporation.

Evaporative cooling is a very common form of cooling buildings for thermal comfort since it is relatively cheap and requires less energy than many other forms of cooling. Human thermal comfort is defined by ASHRAE as the state of mind that expresses satisfaction with the surrounding environment (ASHRAE Standard 55 However evaporative cooling requires an abundant water source as an evaporate, and is only efficient when the relative humidity is low, restricting its effective use to dry climates. Evaporative coolers are colloquially referred to as swamp coolers in the U. S. In other places they are known as desert coolers.

Evaporative cooling is commonly used in cryogenic applications. Cryogenics is often used incorrectly to refer to Cryonics, cryopreserving humans or animals The vapor above a reservoir of cryogenic liquid is pumped away, and the liquid continuously evaporates as long as the liquid's vapor pressure is significant. Vapor pressure (also known as equilibrium vapor pressure or saturation vapor pressure) is the Pressure of a Vapor in equilibrium Evaporative cooling of ordinary helium forms a 1-K pot, which can cool to at least 1. Helium ( He) is a colorless odorless tasteless non-toxic Inert Monatomic Chemical 2 K. Evaporative cooling of helium-3 can provide temperatures below 300 mK. This article is about the elemental isotope For the record label Helium 3 see Muse or A&E Records. Each of these techniques can be used to make cryocoolers, or as components of lower-temperature cryostats such as dilution refrigerators. Cryocoolers are the devices used to reach cryogenic temperatures A Cryostat (cryo=cold and stat=stable is a vessel similar in construction to a Vacuum flask, or Dewar used to maintain cold Cryogenic temperatures A dilution refrigerator is a cryogenic device first proposed by Heinz London. As the temperature decreases, the vapor pressure of the liquid also falls, and cooling becomes less effective. This sets a lower limit to the temperature attainable with a given liquid.

This process has recently been observed to operate on a planetary scale on Pluto and acts as an Anti-Greenhouse Effect. The anti-greenhouse effect is a Neologism used to describe two different effects coming under the header of "the cooling effect an atmosphere has on the ambient temperature

Evaporative cooling is also the last cooling step in order to reach the ultra-low temperatures required for Bose-Einstein Condensation (BEC). A Bose–Einstein condensate (BEC is a State of matter of Bosons confined in an external Potential and cooled to Temperatures very near to Here, so-called forced evaporative cooling is used to selectively remove high-energetic ("hot") atoms from an atom cloud until the remaining cloud is cooled below the BEC transition temperature. For a cloud of 1 million alkali atoms, this temperature is about 1μK.

Evaporative cooler designs

Direct Evaporative Cooling (open circuit) is 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) is similar to direct evaporative cooling, but uses some type of heat exchanger. A heat exchanger is a device built for efficient Heat transfer from one medium to another whether the media are separated by a solid wall so that they never mix or the media The cooled moist air never comes in direct contact with the conditioned environment.

Two-stage Evaporative Cooling, or Indirect-Direct. Traditional evaporative coolers use only a fraction of the energy of vapor-compression or absorption air conditioning systems. Unfortunately, except for in very dry climates, they may increase humidity to a level that makes occupants uncomfortable. Two-stage evaporative coolers do not produce humidity levels as high as that produced by traditional single-stage evaporative coolers.

In the first stage of a two-stage cooler, 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 precooled air passes through a water-soaked pad and picks up humidity as it cools. Because the air supply to the second stage evaporator is pre-cooled, less humidity is added to the air (because cooler air can’t hold as much moisture as warmer air). The result, according to manufacturers, is cool air with a relative humidity between 50 and 70 percent, depending on the climate, compared to a traditional system that produces about 80 percent relative humidity air.

Typical

Typically, residential and industrial evaporative coolers use direct evaporation and can be described as an enclosed metal or plastic box with vented sides containing a centrifugal fan or 'blower', electric motor with pulleys (known as 'sheaves' in HVAC]), and a water pump to wet the evaporative cooling pads. A centrifugal fan (also squirrel-cage fan, as it looks like a Hamster wheel) is a mechanical device for moving Air or other Gases It has a HVAC (pronounced either "H-V-A-C" or occasionally " H-vak " is an Initialism or Acronym that stands for " Heating The units can be mounted on the roof (down draft, or downflow), or exterior walls or windows (side draft, or horizontal flow) of buildings. To cool, the fan draws ambient air through vents on the unit's 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. Thus cooled, moist air is then delivered to the building via a vent in the roof or wall.

Because the cooling air originates outside the building, one or more large vents must exist to allow air to move from inside to outside. Air should only be allowed to pass once through the system, or the cooling effect will decrease. This is due to the air reaching the saturation point. Humidity is the amount of water vapor in the air In daily language the term "humidity" is normally taken to mean Relative humidity. Often 15 or so air changes per hour (ACHs) occur in spaces served by evaporative coolers.

Cooler pads

Traditionally, evaporative cooler pads consist of excelsior (wood wool) (aspen wood fiber) inside a containment net, but more modern materials, such as some plastics and melamin paper, are entering use as cooler-pad media. Excelsior is a wood product made of fibers from the Aspen tree used in packaging cushioning stuffing of stuffed animals and for the cooling pads in home Evaporative Aspens are Trees of the willow family and comprise a section of the Poplar genus Populus sect Wood is hard fibrous lignified structural tissue produced as secondary Xylem in the stems of Woody plants notably trees but also shrubs Fiber or fibre is a class of Materials that are continuous filaments or are in discrete elongated pieces similar to lengths of thread. Melamine resin or melamine formaldehyde (also shortened to melamine) is a hard Thermosetting plastic material made from Melamine and 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 surface area will be more efficient than a one-inch pad.

Evaporative (wet) cooling towers

Main article: Cooling tower

Cooling towers are structures for cooling water or other working media to near-ambient wet bulb temperature. Cooling towers are heat removal devices used to transfer process waste heat to the Atmosphere. Cooling towers are heat removal devices used to transfer process waste heat to the Atmosphere. Wet cooling towers operate on the evaporative cooling principle, but are optimized to cool the water rather than the air. Cooling towers can often be found on large buildings or on industrial sites. They reject heat to the environment from chillers, industrial processes, or the Rankine power cycle, for example. The Rankine cycle is a thermodynamic cycle which converts heat into work

Misting systems

Misting systems work by forcing water via a high pressure pump and tubing through a brass and stainless steel mist nozzle that has an orifice of about 5 micrometres, thereby producing a micro-fine mist. A micrometre ( American spelling: micrometer; symbol µm) is one millionth of a Metre, or equivalently one thousandth of a Millimetre The water droplets that create the mist are so small that they instantly flash evaporate. Flash evaporation can reduce the surrounding air temperature by as much as 35°F (20°C) in just seconds [2]. Flash (or partial Evaporation is the partial Vaporization that occurs when a saturated liquid stream undergoes a reduction in pressure by passing through 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 for many different applications including orchids, pets, livestock, kennels, insect control, odor control, zoos, veterinary clinics, produce cooling, greenhouses, etc.

Misting fans

A misting fan is similar to a humidifier. A humidifier is a household Appliance that increases Humidity (moisture in a single room or in the entire home A fan blows a fine mist of water into the air. If the air is not too humid, the water evaporates, absorbing heat from the air, allowing the misting fan to work as an air conditioner. A misting fan may be used outdoors, especially in a dry climate.

Performance

Understanding evaporative cooling performance requires an understanding of psychrometrics. Psychrometrics or psychrometry are terms used to describe the field of engineering concerned with the determination of physical and thermodynamic properties of gas-vapor mixtures Evaporative cooling performance is dynamic due to changes in external temperature and humidity level. Under typical operating conditions, an evaporative cooler will nearly always deliver air cooler than 27°Celsius (80°Fahrenheit). The Celsius Temperature scale was previously known as the centigrade scale. Fahrenheit is a temperature scale named after Daniel Gabriel Fahrenheit (1686–1736 a German Physicist who proposed it in 1724 A typical residential 'swamp cooler' in good working order should cool air to within 3°C–4°C (6°F–8°F) of the wet-bulb temperature. The wet-bulb temperature is a type of Temperature measurement that reflects the physical properties of a system with a mixture of a Gas and a

In practice, it may be difficult to predict swamp cooler performance from standard weather report information, because weather reports usually contain the dewpoint and relative humidity, but not the wet bulb temperature. The dew point (sometimes spelled dewpoint) is the Temperature to which a given parcel of Air must be cooled at constant Barometric pressure, Relative humidity is a measurement of the amount of Water vapor that exists in a gaseous mixture of air and water However, you may use either of two methods to estimate performance:

• Use a Psychrometric chart to calculate wet bulb temperature, and then add 6°F–8°F as described above. Psychrometrics or psychrometry are terms used to describe the field of engineering concerned with the determination of physical and thermodynamic properties of gas-vapor mixtures
• Use a rule of thumb which estimates that the wet bulb temperature is approximately equal to the ambient temperature, minus two thirds of the difference between the ambient temperature and the dewpoint. A rule of thumb is a principle with broad application that is not intended to be strictly accurate or reliable for every situation As before, add 6°F–8°F as described above.

Some rough examples clarify this relationship.

• At 32°C (90°F) and 15% relative humidity, air may be cooled to nearly 16°C (60°F). The dew point for these conditions is 2°C (~36°F).
• At 32°C (90°F) and 50% relative humidity, air may be cooled to about 24°C (75°F). The dew point for these conditions is 20°C (~68°F).
• At 40°C (105°F) and 15% relative humidity, air may be cooled to nearly 21°C (70°F). The dew point for these conditions is 8°C (~47°F).

Because evaporative coolers perform best in dry conditions, they are widely used and most effective in arid, desert regions such as the southwestern USA and northern Mexico. A desert is a Landscape or region that receives very little precipitation. The Southwestern area of the United States could be defined as the states west of the Mississippi River, with the qualification of a certain northern limit such as the 37 The United Mexican States ( or commonly Mexico (ˈmɛksɪkoʊ () is a federal constitutional Republic in North America.

(Cooling examples extracted from the June 25, 2000 University of Idaho publication, "Homewise"). Events 524 - Battle of Vézeronce, the Franks defeat the Burgundians 2000 ( MM) was a Leap year that started on Saturday of the Common Era, in accordance with the Gregorian calendar.

Comparison to air conditioning

Comparison of Evaporative cooling to phase-change air conditioning:

Advantages

Less expensive to install

• Estimated cost for installation is 1/8 to 1/2 that of refrigerated air conditioning

Less expensive to operate

• Estimated cost of operation is 1/4 that of refrigerated air. The term air conditioning refers to the cooling and dehumidification of indoor air for Thermal comfort.
• Power consumption is limited to the fan and water pump vs. compressors, pumps, and blowers. A gas compressor is a mechanical device that increases the Pressure of a Gas by reducing its Volume. For information on Wikipedia project-related discussions see WikipediaVillage pump. A mechanical fan is an electrically powered device used to produce an airflow for the purpose of creature comfort (particularly in the heat ventilation, exhaust

Ventilation air

• The constant and high volumetric flow rate of air through the building reduces the age-of-air in the building dramatically.
• Evaporative cooling increases humidity, which, in dry climates, may improve thermal comfort. Humidity is the amount of water vapor in the air In daily language the term "humidity" is normally taken to mean Relative humidity. Human thermal comfort is defined by ASHRAE as the state of mind that expresses satisfaction with the surrounding environment (ASHRAE Standard 55

Disadvantages

Performance

• High temperature, high humidity outside conditions decrease the cooling capability of the evaporative cooler.
• No dehumidification. A dehumidifier is a Household appliance that reduces the level of Humidity in air usually for health reasons as humid air can cause Mold and Traditional air conditioners remove moisture from the air, which is usually a design requirement except in very dry locations. Evaporative cooling adds moisture, which, in dry climates, may improve thermal comfort. Human thermal comfort is defined by ASHRAE as the state of mind that expresses satisfaction with the surrounding environment (ASHRAE Standard 55

Comfort

• The air supplied by the evaporative cooler is typically 80–90% relative humidity.
• Very humid air reduces the evaporation rate of moisture from the skin, nose, lungs, and eyes.
• High humidity in air accelerates corrosion. Corrosion means the breaking down of essential properties in a material due to Chemical reactions with its surroundings This can considerably shorten the life of electronic and other equipment.
• High humidity in air may cause condensation. Condensation is the change of the physical state of aggregation (or simply state of matter from gaseous phase into liquid phase This can be a problem for some situations (e. g. , electrical equipment, computers, paper/books, old wood).

Water

• Evaporative coolers require a constant supply of water to wet the pads.
• Water high in mineral content will leave mineral deposits on the pads and interior of the cooler. A mineral is a naturally occurring substance formed through geological processes that has a characteristic chemical composition a highly ordered atomic structure and specific Water softeners, bleed-off, and refill systems may reduce this problem. A water softener reduces the dissolved Calcium, Magnesium, and to some degree Manganese and Ferrous iron ion concentration in Hard water
• The water supply line needs protection against freeze bursting during off-season, winter temperatures. The cooler itself needs to be drained too, as well as cleaned periodically and the pads replaced.

Miscellaneous

• Pollen, odors, and other outdoor contaminants may be blown into the building unless sufficient filtering is in place. Pollen is a fine to coarse powder consisting of microgametophytes ( pollen grains) which produce the male Gametes (sperm cells of
• The vents that allow air to exit the building may pose a physical security risk. Physical security describes measures that prevent or deter Attackers from accessing a facility resource or information stored on physical media
• Asthma patients may need to avoid evaporatively cooled environments. Asthma is a chronic Condition involving the Respiratory system in which the airways occasionally constrict become inflamed, and are

Health Concerns

Evaporative coolers, like all equipment, require maintenance. Legionnaire's Disease, caused by the bacterium Legionella pneumophila and related bacteria . Legionellosis is an Infectious disease caused by Bacteria belonging to the Genus Legionella. Legionella is a Gram negative Bacterium, including species that cause Legionellosis or Legionnaires' disease most notably L The Bacteria ( singular: bacterium) are a large group of unicellular Microorganisms Typically a few Micrometres in length bacteria have . . "may be found in purpose built water systems such as cooling towers, evaporative condensers. . . " ^[2] As such, it is critical that evaporative coolers be properly installed and adequately maintained according to their manufacturers' recommendations.

See also

• Air conditioning
• Cooling tower
• Cooling tower system
• Pot-in-pot refrigerator
• Psychrometrics
• Dew point
• Evaporation
• Humidity
• HVAC
• Architectural engineering
• Building engineering

References

External links

• Holladay, April (2001). A swamp cooler cools air by evaporation. WonderQuest Weekly Q&A science column. USAToday. com. Retrieved on 2006-07-14. Year 2006 ( MMVI) was a Common year starting on Sunday of the Gregorian calendar. Events 1223 - Louis VIII becomes King of France upon the death of his father Philip II of France.
• Mithra, S. (2006). What is a Swamp Cooler?. clear answers for common questions. Wisegeek. com. Retrieved on 2006-07-14. Year 2006 ( MMVI) was a Common year starting on Sunday of the Gregorian calendar. Events 1223 - Louis VIII becomes King of France upon the death of his father Philip II of France.
• PATH Tech Inventory: Two Stage Evaporative Cooler
• PATH Tech Inventory: Evaporative Cooler
• Evaporative cooling simulation

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