Air Works Flashcards
Psychrometry
Is the branch of physics relating to the measurement or determination of atmospheric conditions particularly the amount of moisture mixed in the air.
Saturation
Is the state of being completely filled charged, or treated with something so the no more can be taken in.
Atmospheric pressure
Is the pressure exerted on the earths surface by the weight of the air and moisture above it. A unit of pressure equals about 14.696 or 29.92 inches Hg mercury at 32 degrees F at sea level.
Also called barometric pressure. Pressure is measured in pounds per square inch.
Dry bulb temperature
Is the temperature of air, measured by a thermometer freely exposed to the air but shielded from radiation and moisture.
Grain
Unit of weight equal to one 7000th of a pound. (.06480 grams). It is used to indicate the amount of moisture in the air.
Enthalphy
Is the total amount of heat (both latent and sensible in one pound of a substance that is calculated from accepted base of 32 degrees F. For refrigeration the accepted bases is -40 degrees F. Expressed in BTU/lb.
Vapor pressure
Is the pressure exerted by a saturated vapor above its own liquid in a closed container.
Wet bulb
The lowest temperature the can be reached by the evaporation of water. It is the temperature you feel when your skin is wet and exposed to moving air.
Dew Point
(Dpt) corresponds to the temperature at which air becomes completely saturated. If moist air is cooled, it cannot hold the same amount of moisture. At some pint the moisture will condense out of the air onto any surface.
Sling Psychrometer
A Humidity measuring device with wet and dry bulb thermometers. It is rapidly moved through the air when measuring humidity
Standard air (conditions)
Used as a basis for air conditioning calculations. These are temperature of 68 F, a pressure of 29.9 inches of Hg, a specific volume of 13.333 cubic foot, a specific density of .075 pounds per cubic foot, and relative humidity of 30%.
Specific Volume
Volume (in cubic feet) that one pound of air occupies at a specific set of conditions. The inverse relationship of density.
Air is 13.33 ft3/lb.
Hydrogen is 179 ft3/lb.
Specific density
A Statement of mass per unit of volume measurement.
Relative Humidity
Measure of how much water vapor air is holding compared to how much it holds is saturated.
Comfort
Temperature, humidity,air movement, and air cleanliness