All designs yield advantage of the actuality that baptize has one of the accomplished accepted enthalpy of dehydration (latent calefaction of vaporization) ethics of any accepted substance.
Evaporative acknowledgment illustration
Direct evaporative cooling (open circuit) is acclimated to lower the temperature of air by application abeyant calefaction of evaporation, alteration aqueous baptize to baptize vapor. In this process, the activity in the air does not change. Balmy dry air is afflicted to air-conditioned clammy air. The calefaction of the alfresco air is acclimated to clear water.
Indirect evaporative cooling (closed circuit) is agnate to absolute evaporative cooling, but uses some blazon of calefaction exchanger. The cooled clammy air never comes in absolute acquaintance with the conditioned environment.
Two-stage evaporative cooling, or indirect-direct. Acceptable evaporative coolers use alone a atom of the activity of vapor-compression or assimilation air conditioning systems. Unfortunately, except in actual dry climates they access clamminess to a akin that makes occupants uncomfortable. Two-stage evaporative coolers do not aftermath clamminess levels as top as that produced by acceptable single-stage evaporative coolers.
In the aboriginal date of a two-stage cooler, balmy air is pre-cooled alongside after abacus clamminess (by casual central a calefaction exchanger that is cooled by dehydration on the outside). In the absolute stage, the pre-cooled air passes through a water-soaked pad and picks up clamminess as it cools. Since the air accumulation is pre-cooled in the aboriginal stage, beneath clamminess is bare in the absolute date to ability the adapted cooling temperatures. The result, according to manufacturers, is acknowledgment air with a about clamminess amid 50 and 70 percent, depending on the climate, compared to a acceptable arrangement that produces about 70–80 percent about clamminess air.
edit Typical
Typically, residential and automated evaporative coolers use absolute dehydration and can be declared as an amid metal or artificial box with vented abandon absolute a centrifugal fan or 'blower', electric motor with pulleys (known as 'sheaves' in HVAC), (or a direct-driven axial fan), and a baptize pump to wet the evaporative cooling pads. The units can be army on the roof (down draft, or downflow), or exoteric walls or windows (side draft, or accumbent flow) of buildings. To cool, the fan draws ambient air through vents on the unit's abandon and through the clammy pads. Calefaction in the air evaporates baptize from the pads which are consistently re-dampened to abide the cooling process. Thus cooled, clammy air is again delivered to the architecture via a aperture in the roof or wall.
Because the cooling air originates alfresco the building, one or added ample vents have to abide to acquiesce air to move from central to outside. Air should alone be accustomed to canyon already through the system, or the cooling aftereffect will decrease. This is due to the air extensive the assimilation point. Generally 15 or so air changes per hour (ACHs) action in spaces served by evaporative coolers.
Didcot Ability Station cooling towers
edit Acknowledgment pads
Question book-new.svg
This area does not adduce any references or sources. Please advice advance this area by abacus citations to reliable sources. Unsourced actual may be challenged and removed. (September 2010)
Traditionally, evaporative acknowledgment pads abide of excelsior (wood wool) (aspen copse fiber) central a ascendancy net, but added avant-garde materials, such as some plastics and melamine paper, are entering use as cooler-pad media. Copse absorbs some of the water, which allows the copse fibers to air-conditioned casual air to a lower temperature than some constructed materials.
edit Evaporative (wet) cooling towers
Main article: Cooling tower
Cooling building are structures for cooling baptize or added alive media to near-ambient wet-bulb temperature. Wet cooling building accomplish on the evaporative cooling principle, but are optimized to air-conditioned the baptize rather than the air. Cooling building can generally be begin on ample barrio or on automated sites. They alteration calefaction to the ambiance from chillers, automated processes, or the Rankine ability cycle, for example.
edit Misting systems
Mist spraying arrangement with baptize pump beneath
Misting systems plan by banishment baptize via a top burden pump and tubing through a assumption and stainless animate brume bill that has an breach of about 5 micrometres, thereby bearing a micro-fine mist. The baptize aerosol that actualize the brume are so baby that they instantly beam evaporate. Beam dehydration can abate the surrounding air temperature by as abundant as 35 F° (20 C°) in just seconds.8 For patio systems, it is ideal to arise the brume band about 8 to 10 anxiety (2.4 to 3.0 m) aloft the arena for optimum cooling. Misting is acclimated for applications such as flowerbeds, pets, livestock, kennels, insect control, odor control, zoos, veterinary clinics, aftermath cooling and greenhouses.
edit Misting fans
A misting fan is agnate to a humidifier. A fan assault a accomplished brume of baptize into the air. If the air is not too humid, the baptize evaporates, arresting calefaction from the air, acceptance the misting fan to plan as an air conditioner. A misting fan may be acclimated outdoors, abnormally in a dry climate.
edit Performance
Understanding evaporative cooling achievement requires an compassionate of psychrometrics. Evaporative cooling achievement is activating due to changes in alien temperature and clamminess level. A residential acknowledgment should air-conditioned air to aural 3–4 C° (5–7 F°) of the agnate wet-bulb temperature.
It is simple to adumbrate acknowledgment achievement from accepted acclimate address information. Because acclimate letters usually accommodate the dewpoint and about humidity, but not the wet-bulb temperature, a Psychrometric blueprint have to be acclimated to analyze the wet ball temperature. Already the wet ball temperature and the dry ball temperature are articular the cooling achievement or abrogation air temperature of the acknowledgment may be determined:
TLA = TDB – ((TDB – TWB) x E)
TLA = Abrogation Air Temp
TDB = Dry Ball Temp
TWB = Wet Ball Temp
E = Ability of the evaporative media.
Evaporative media ability usually runs amid 80% to 90% and the dehydration ability drops actual little over time. Archetypal aspen pads acclimated in residential evaporative coolers action about 85% ability while CELdek blazon of evaporative media action efficiencies of 90% + depending on air velocity. The celdec media is added generally acclimated in ample bartering and automated installations.
As an example, in Las Vegas, Nevada, with a archetypal summer architecture day of 108°F DB/66°F WB or about 8% about humidity, the abrogation air temperature of a residential acknowledgment would be:
TLA = 108° – ((108° – 66°) x 85% efficiency)
TLA = 72.3°F
However, either of two methods can be acclimated to estimatte performance:
Use a Psychrometric blueprint to account wet ball temperature, and again add 6–8 F° as declared above.
Use a aphorism of deride which estimates that the wet ball temperature is about according to the ambient temperature, bare one third of the aberration amid the ambient temperature and the dew point. As before, add 6–8 F° as declared above.
Some examples analyze this relationship:
At 32 °C (90 °F) and 15% about humidity, air may be cooled to about 16 °C (61 °F). The dew point for these altitude is 2 °C (36 °F).
At 32 °C (90 °F) and 50% about humidity, air may be cooled to about 24 °C (75 °F). The dew point for these altitude is 20 °C (68 °F).
At 40 °C (104 °F) and 15% about humidity, air may be cooled to about 21 °C (70 °F). The dew point for these altitude is 8 °C (46 °F).
(Cooling examples extracted from the June 25, 2000 University of Idaho publication, "Homewise").
Because evaporative coolers accomplish best in dry conditions, they are broadly acclimated and a lot of able in arid, arid regions such as the southwestern USA and arctic Mexico.
The aforementioned blueprint indicates why evaporative coolers are of bound use in awful boiling environments: for example, a hot August day in Tokyo may be 30 °C (86 °F), 85% about humidity, 1,005 hPa pressure. This gives dew point 27.2 °C (81.0 °F) and wet-bulb temperature 27.88 °C (82.18 °F). According to the blueprint above, at 85% ability air may be cooled alone down to 28.2 °C (82.8 °F) which makes it absolutely impractical.
Evaporative acknowledgment illustration
Direct evaporative cooling (open circuit) is acclimated to lower the temperature of air by application abeyant calefaction of evaporation, alteration aqueous baptize to baptize vapor. In this process, the activity in the air does not change. Balmy dry air is afflicted to air-conditioned clammy air. The calefaction of the alfresco air is acclimated to clear water.
Indirect evaporative cooling (closed circuit) is agnate to absolute evaporative cooling, but uses some blazon of calefaction exchanger. The cooled clammy air never comes in absolute acquaintance with the conditioned environment.
Two-stage evaporative cooling, or indirect-direct. Acceptable evaporative coolers use alone a atom of the activity of vapor-compression or assimilation air conditioning systems. Unfortunately, except in actual dry climates they access clamminess to a akin that makes occupants uncomfortable. Two-stage evaporative coolers do not aftermath clamminess levels as top as that produced by acceptable single-stage evaporative coolers.
In the aboriginal date of a two-stage cooler, balmy air is pre-cooled alongside after abacus clamminess (by casual central a calefaction exchanger that is cooled by dehydration on the outside). In the absolute stage, the pre-cooled air passes through a water-soaked pad and picks up clamminess as it cools. Since the air accumulation is pre-cooled in the aboriginal stage, beneath clamminess is bare in the absolute date to ability the adapted cooling temperatures. The result, according to manufacturers, is acknowledgment air with a about clamminess amid 50 and 70 percent, depending on the climate, compared to a acceptable arrangement that produces about 70–80 percent about clamminess air.
edit Typical
Typically, residential and automated evaporative coolers use absolute dehydration and can be declared as an amid metal or artificial box with vented abandon absolute a centrifugal fan or 'blower', electric motor with pulleys (known as 'sheaves' in HVAC), (or a direct-driven axial fan), and a baptize pump to wet the evaporative cooling pads. The units can be army on the roof (down draft, or downflow), or exoteric walls or windows (side draft, or accumbent flow) of buildings. To cool, the fan draws ambient air through vents on the unit's abandon and through the clammy pads. Calefaction in the air evaporates baptize from the pads which are consistently re-dampened to abide the cooling process. Thus cooled, clammy air is again delivered to the architecture via a aperture in the roof or wall.
Because the cooling air originates alfresco the building, one or added ample vents have to abide to acquiesce air to move from central to outside. Air should alone be accustomed to canyon already through the system, or the cooling aftereffect will decrease. This is due to the air extensive the assimilation point. Generally 15 or so air changes per hour (ACHs) action in spaces served by evaporative coolers.
Didcot Ability Station cooling towers
edit Acknowledgment pads
Question book-new.svg
This area does not adduce any references or sources. Please advice advance this area by abacus citations to reliable sources. Unsourced actual may be challenged and removed. (September 2010)
Traditionally, evaporative acknowledgment pads abide of excelsior (wood wool) (aspen copse fiber) central a ascendancy net, but added avant-garde materials, such as some plastics and melamine paper, are entering use as cooler-pad media. Copse absorbs some of the water, which allows the copse fibers to air-conditioned casual air to a lower temperature than some constructed materials.
edit Evaporative (wet) cooling towers
Main article: Cooling tower
Cooling building are structures for cooling baptize or added alive media to near-ambient wet-bulb temperature. Wet cooling building accomplish on the evaporative cooling principle, but are optimized to air-conditioned the baptize rather than the air. Cooling building can generally be begin on ample barrio or on automated sites. They alteration calefaction to the ambiance from chillers, automated processes, or the Rankine ability cycle, for example.
edit Misting systems
Mist spraying arrangement with baptize pump beneath
Misting systems plan by banishment baptize via a top burden pump and tubing through a assumption and stainless animate brume bill that has an breach of about 5 micrometres, thereby bearing a micro-fine mist. The baptize aerosol that actualize the brume are so baby that they instantly beam evaporate. Beam dehydration can abate the surrounding air temperature by as abundant as 35 F° (20 C°) in just seconds.8 For patio systems, it is ideal to arise the brume band about 8 to 10 anxiety (2.4 to 3.0 m) aloft the arena for optimum cooling. Misting is acclimated for applications such as flowerbeds, pets, livestock, kennels, insect control, odor control, zoos, veterinary clinics, aftermath cooling and greenhouses.
edit Misting fans
A misting fan is agnate to a humidifier. A fan assault a accomplished brume of baptize into the air. If the air is not too humid, the baptize evaporates, arresting calefaction from the air, acceptance the misting fan to plan as an air conditioner. A misting fan may be acclimated outdoors, abnormally in a dry climate.
edit Performance
Understanding evaporative cooling achievement requires an compassionate of psychrometrics. Evaporative cooling achievement is activating due to changes in alien temperature and clamminess level. A residential acknowledgment should air-conditioned air to aural 3–4 C° (5–7 F°) of the agnate wet-bulb temperature.
It is simple to adumbrate acknowledgment achievement from accepted acclimate address information. Because acclimate letters usually accommodate the dewpoint and about humidity, but not the wet-bulb temperature, a Psychrometric blueprint have to be acclimated to analyze the wet ball temperature. Already the wet ball temperature and the dry ball temperature are articular the cooling achievement or abrogation air temperature of the acknowledgment may be determined:
TLA = TDB – ((TDB – TWB) x E)
TLA = Abrogation Air Temp
TDB = Dry Ball Temp
TWB = Wet Ball Temp
E = Ability of the evaporative media.
Evaporative media ability usually runs amid 80% to 90% and the dehydration ability drops actual little over time. Archetypal aspen pads acclimated in residential evaporative coolers action about 85% ability while CELdek blazon of evaporative media action efficiencies of 90% + depending on air velocity. The celdec media is added generally acclimated in ample bartering and automated installations.
As an example, in Las Vegas, Nevada, with a archetypal summer architecture day of 108°F DB/66°F WB or about 8% about humidity, the abrogation air temperature of a residential acknowledgment would be:
TLA = 108° – ((108° – 66°) x 85% efficiency)
TLA = 72.3°F
However, either of two methods can be acclimated to estimatte performance:
Use a Psychrometric blueprint to account wet ball temperature, and again add 6–8 F° as declared above.
Use a aphorism of deride which estimates that the wet ball temperature is about according to the ambient temperature, bare one third of the aberration amid the ambient temperature and the dew point. As before, add 6–8 F° as declared above.
Some examples analyze this relationship:
At 32 °C (90 °F) and 15% about humidity, air may be cooled to about 16 °C (61 °F). The dew point for these altitude is 2 °C (36 °F).
At 32 °C (90 °F) and 50% about humidity, air may be cooled to about 24 °C (75 °F). The dew point for these altitude is 20 °C (68 °F).
At 40 °C (104 °F) and 15% about humidity, air may be cooled to about 21 °C (70 °F). The dew point for these altitude is 8 °C (46 °F).
(Cooling examples extracted from the June 25, 2000 University of Idaho publication, "Homewise").
Because evaporative coolers accomplish best in dry conditions, they are broadly acclimated and a lot of able in arid, arid regions such as the southwestern USA and arctic Mexico.
The aforementioned blueprint indicates why evaporative coolers are of bound use in awful boiling environments: for example, a hot August day in Tokyo may be 30 °C (86 °F), 85% about humidity, 1,005 hPa pressure. This gives dew point 27.2 °C (81.0 °F) and wet-bulb temperature 27.88 °C (82.18 °F). According to the blueprint above, at 85% ability air may be cooled alone down to 28.2 °C (82.8 °F) which makes it absolutely impractical.
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