CPS TEMP-SEEKER TM360 Руководство пользователя - Страница 8
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Печатать страницуPSYCHROMETRIC CHART
Psychrometry is the science which studies the properties of moist air. A psychrometric
chart graphically illustrates the relationship between air temperature and relative humidity
as well as other properties. Air Temperature is a measure of the heat content of air.
Three different temperature measurements are used in the psychrometric chart.
1. Dry Bulb temperature refers basically to the ambient air temperature not affected
by the moisture in the air. The dry bulb scale is located at the base of the chart.
Vertical lines indicate constant dry bulb temperatures.
2. Wet Bulb temperature reflects the cooling effect of evaporating water. The cooling
effect of the evaporating water causes a lower temperature compared to the dry
bulb air temperature. The wet bulb temperature scale is located along the curved
upper left portion of the chart. The sloping lines indicate equal wet bulb
temperatures.
3. Dew Point is the temperature at which water vapor starts to condense out of the
air; the temperature at which air becomes completely saturated. Water will
condense on a surface, such as a building wall or pitcher of ice water, that is at or
below the dew point temperature of the air. Above this temperature the moisture
will stay in the air. The dew point temperature scale is located along the same
curved portion of the chart as the wet bulb temperature scale. However, horizontal
lines indicate equal dew point temperatures. If the dew point temperature is close
to the air temperature, the relative humidity is high, and if the dew point is
well below the air temperature, the relative humidity is low.
Relative Humidity is a measure of how much moisture is present compared to how
much moisture the air could hold at that temperature expressed as a percentage. Lines
representing conditions of equal relative humidities sweep from the lower left to the
upper right of the psychrometric chart. The 100 percent relative humidity (saturation)
line corresponds to the wet bulb and the dew point temperature scale line. The line
for zero percent relative humidity falls along the dry bulb temperature scale line.
The versatility of the psychrometric chart lies in the fact that by knowing just two
properties of moist air, the other properties can be determined.
Dry Bulb Temperature, ˚F
Dew Point Temperature, ˚F
Wet Bulb Temperature, ˚F
Relative Humidity, %
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