Evaporative cooler - Wikipedia, the free encyclopedia. A . Evaporative cooling differs from typical air conditioning systems which use vapor- compression or absorption refrigeration cycles. Evaporative cooling works by employing water's large enthalpy of vaporization. The temperature of dry air can be dropped significantly through the phase transition of liquid water to water vapor (evaporation), which can cool air using much less energy than refrigeration. In extremely dry climates, evaporative cooling of air has the added benefit of conditioning the air with more moisture for the comfort of building occupants. The cooling potential for evaporative cooling is dependent on the wet bulb depression, the difference between dry- bulb temperature and wet- bulb temperature. In arid climates, evaporative cooling can reduce energy consumption and total equipment for conditioning as an alternative to compressor- based cooling. In climates not considered arid, indirect evaporative cooling can still take advantage of the evaporative cooling process without increasing humidity. Passive evaporative cooling strategies offer the same benefits of mechanical evaporative cooling systems without the complexity of equipment and ductwork. Overview. Nowadays Iranians have changed the windcatcher into an evaporative cooler (Coolere . A typical design, as shown in a 1. In 1. 98. 6, two researchers at the University of Arizona, Tucson, W. Thompson, constructed the first passive evaporative cooling tower in Tucson, AZ. This performance data from this experimental facility became the foundation of today. ![]() Evaporative Cooling Design Guidelines Manual v EVAPORATIVE COOLING DESIGN GUIDELINES MANUAL FOR NEW MEXICO SCHOOLS AND COMMERCIAL BUILDINGS TABLE OF CONTENTS PREFACE. Go To Home Page; Go To Browse Page; Open Tools Menu. Go To Interactive Equations Page; Go To Periodic Table Page; Go To. Air-Conditioning and Heating Systems. Evaporative Air-Cooling Equipment. Evaporative cooling is the addition of water vapor into air, which causes a lowering of the temperature of the air. The energy needed to evaporate the water is taken from the air in the form of sensible heat, which affects the temperature of the air, and converted into latent heat, the energy present in the water vapor component of the air, whilst the air remains at a constant enthalpy value. This conversion of sensible heat to latent heat is known as an adiabatic process because it occurs at a constant enthalpy value. Evaporative cooling therefore causes a drop in the temperature of air proportional to the sensible heat drop and an increase in humidity proportional to the latent heat gain. Evaporative cooling can be visualized using a psychrometric chart by finding the initial air condition and moving along a line of constant enthalpy toward a state of higher humidity. The amount of heat transfer depends on the evaporation rate, however for each kilogram of water vaporized 2,2. J of energy (about 8. BTU per pound of pure water, at 9. The evaporation rate depends on the temperature and humidity of the air, which is why sweat accumulates more on humid days, as it does not evaporate fast enough. Vapor- compression refrigeration uses evaporative cooling, but the evaporated vapor is within a sealed system, and is then compressed ready to evaporate again, using energy to do so. A simple evaporative cooler's water is evaporated into the environment, and not recovered. In an interior space cooling unit, the evaporated water is introduced into the space along with the now- cooled air; in an evaporative tower the evaporated water is carried off in the airflow exhaust. Other types of phase- change cooling. A separate compartment inside the can contains a desiccant and a liquid. Just before drinking, a tab is pulled so that the desiccant comes into contact with the liquid and dissolves. As it does so it absorbs an amount of heat energy called the latent heat of fusion. Evaporative cooling works with the phase change of liquid into vapor and the latent heat of vaporization, but the self- cooling can uses a change from solid to liquid, and the latent heat of fusion to achieve the same result. Applications. A porous earthenware vessel would cool water by evaporation through its walls; frescoes from about 2. BC show slaves fanning jars of water to cool rooms. The colored lines illustrate the potential of direct and indirect evaporative cooling strategies to expand the comfort range in summer time. It is mainly explained by the combination of a higher air speed on one hand and elevated indoor humidity when the region permits the direct evaporative cooling strategy on the other hand. Evaporative cooling strategies that involve the humidification of the air should be implemented in dry condition where the increase in moisture content stays below recommendations for occupant. Evaporative Air Conditioning Handbook: John Watt: 9780412011511: Books - Amazon.ca. Amazon.ca Try Prime Books Go. Sign in Your Account Try Prime.Passive cooling towers lack the control that traditional HVAC systems offer to occupants. However, the additional air movement provided into the space can improve occupant comfort. Evaporative cooling is most effective when the relative humidity is on the low side, limiting its popularity to dry climates. Evaporative cooling raises the internal humidity level significantly, which desert inhabitants may appreciate as the moist air re- hydrates dry skin and sinuses. Therefore, assessing typical climate data is an essential procedure to determine the potential of evaporative cooling strategies for a building. The three most important climate considerations are dry- bulb temperature, wet- bulb temperature, and wet- bulb depression during the summer design day. It is important to determine if the wet- bulb depression can provide sufficient cooling during the summer design day. By subtracting the wet- bulb depression from the outside dry- bulb temperature, one can estimate the approximate air temperature leaving the evaporative cooler. It is important to consider that the ability for the exterior dry- bulb temperature to reach the wet- bulb temperature depends on the saturation efficiency. A general recommendation for applying direct evaporative cooling is to implement it in places where the wet- bulb temperature of the outdoor air does not exceed 2. Despite this lower value, this climate is still suitable for this technique. Evaporative cooling is especially well suited for climates where the air is hot and humidity is low. Buy Evaporative Air Conditioning Handbook by John Watt (ISBN: 9780412011511) from Amazon's Book Store. Free UK delivery on eligible orders. Skickas inom 2-5 vardagar. Evaporative Air Conditioning Handbook. 28-06-2016 2/4 Evaporative Air Conditioning Handbook. Other Files Available to Download In the United States, the western/mountain states are good locations, with evaporative coolers prevalent in cities like Denver, Salt Lake City, Albuquerque, El Paso, Tucson, and Fresno. Evaporative air conditioning is also popular and well- suited to the southern (temperate) part of Australia. In dry, arid climates, the installation and operating cost of an evaporative cooler can be much lower than that of refrigerative air conditioning, often by 8. However, evaporative cooling and vapor- compression air conditioning are sometimes used in combination to yield optimal cooling results. Some evaporative coolers may also serve as humidifiers in the heating season. Even in regions that are mostly arid, short periods of high humidity may prevent evaporative cooling from being an effective cooling strategy. An example of this event is the monsoon season in southern Arizona in July and August. In locations with moderate humidity 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) often employ evaporative cooling. In highly humid climates, evaporative cooling may have little thermal comfort benefit beyond the increased ventilation and air movement it provides. Other examples. 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. Evaporative cooling of ordinary helium forms a 1- K pot, which can cool to at least 1. K. Evaporative cooling of helium- 3 can provide temperatures below 3. K. These techniques can be used to make cryocoolers, or as components of lower- temperature cryostats such as dilution refrigerators. 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. Evaporative cooling is also the last cooling step in order to reach the ultra- low temperatures required for Bose. Here, so- called forced evaporative cooling is used to selectively remove high- energetic (. For a cloud of 1 million alkali atoms, this temperature is about 1. Examples include the Space Shuttle, the Apollo. Command/Service Module (CSM), Lunar Module and Portable Life Support System. The Apollo CSM and the Space Shuttle also had radiators, and the Shuttle could evaporate ammonia as well as water. The Apollo spacecraft used sublimators, compact and largely passive devices that dump waste heat in water vapor (steam) that is vented to space. The water expended is often available in surplus from the fuel cells used by many manned spacecraft to produce electricity. However the ice crystals from dumped urine, water etc., which are flying through space at orbital velocities, have been found to . Because of this, evaporative coolers use only a fraction of the energy of vapor- compression or absorption air conditioning systems. Unfortunately, except in very dry climates, the single- stage (direct) cooler can increase relative humidity (RH) to a level that makes occupants uncomfortable. Indirect and Two- stage evaporative coolers keep the RH lower. Direct evaporative cooling. In this process, the energy in the air does not change. Warm dry air is changed to cool moist air. The heat of the outside air is used to evaporate water. The RH increases to 7. The moist air has to be continually released to outside or else the air becomes saturated and evaporation stops. A mechanical direct evaporative cooler unit uses a fan to draw air through a wetted membrane, or pad, which provides a large surface area for the evaporation of water into the air.
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