| Absolute humidity | (specific humidity or humidity ratio) is the mass of water vapor present in a unit mass of dry air; that is, it is the ratio of the mass of water vapor to the mass of dry air in atmospheric air.
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| Adiabatic saturation process | is the process in which a steady stream of unsaturated air of unknown specific humidity is passed through a long insulated channel that contains a pool of water. As the air flows over the water, some water will evaporate and mix with the airstream. The moisture content of air will increase during this process, and its temperature will decrease, since part of the latent heat of vaporization of the water that evaporates will come from the air. If the channel is long enough, the airstream will exit as saturated air (100 percent relative humidity) at the exit temperature.
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| Adiabatic saturation temperature | is the exit temperature that air attains in the adiabatic saturation process.
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| Atmospheric air | is the air in the atmosphere, which normally contains some water vapor (or moisture).
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| Cooling pond | is a large lake open to the atmosphere into which warm water containing waste heat is pumped. Heat transfer from the pond surface to the atmosphere is very slow; thus, the cooling pond requires much more surface area than that of a spray pond to achieve the same cooling.
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| Dehumidifying | is the process of removing moisture from atmospheric air.
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| Dew-point temperature | is defined as the temperature at which condensation begins when the air is cooled at constant pressure.
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| Dry air | is air that contains no water vapor.
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| Dry-bulb temperature | is the ordinary temperature of atmospheric air.
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| Evaporative coolers | also known as swamp coolers. Use evaporative cooling based on the principle that as water evaporates, the latent heat of vaporization is absorbed from the water body and the surrounding air. As a result, both the water and the air are cooled during the process.
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| Forced-draft cooling tower, | or induced-draft cooling tower, is a wet cooling tower in which the air is drawn through the tower by fans.
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| Humidity ratio | (see absolute humidity)
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| Humidifying | is the process of adding moisture to atmospheric air.
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| Natural-draft cooling tower | uses the naturally occurring density gradients between the inside air-water vapor mixture and the outside air which create an airflow from the bottom to the top of a wet cooling tower.
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| Psychrometric chart | presents the properties of atmospheric air at a specified pressure and two independent intensive properties. The psychrometric chart is a plot of absolute humidity versus dry-bulb temperature and shows lines of constant relative humidity, wet-bulb temperature, specific volume, and enthalpy for the atmospheric air.
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| Relative humidity | is a measure of the amount of moisture the air holds relative to the maximum amount the air can hold at the same temperature. The relative humidity can be expressed as the ratio of the vapor pressure to the saturation pressure of water at that temperature.
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| Saturated air | is air which can hold no more moisture at its state. Any moisture introduced into saturated air will condense.
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| Simple cooling | is the process of lowering the temperature of atmospheric air when no moisture is removed.
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| Simple heating | is the process of raising the temperature of atmospheric air when no moisture is added.
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| Sling psychrometer | is a device with both a dry-bulb thermometer and a wet-bulb temperature mounted on the frame of the device so that when it is swung through the air both the wet-and dry-bulb temperatures can be read simultaneously.
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| Specific humidity | (see absolute humidity)
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| Spray pond | is a pond where warm water is sprayed into the air and is cooled by the air as it falls into the pond. Spray ponds require 25 to 50 times the area of a cooling tower because water loss due to air drift is high.
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| Vapor pressure | is usually considered to be the partial pressure of water vapor in atmospheric air.
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| Waste heat | is energy that must be dissipated to the atmosphere from a process such as the heat transferred from condensing steam in the condenser of a steam power plant.
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| Wet-bulb temperature | is temperature measured by using a thermometer whose bulb is covered with a cotton wick saturated with water and blowing air over the wick.
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| Wet cooling tower | is essentially a semienclosed evaporative cooler.
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