What three environmental conditions have the most effect on comfort?
Temperature, humidity, and air movement.
41-2) List four ways the human body expels
... [Show More] heat?
Conduction
Convection
Radiation
Evaporation
41-3) Why does the air’s relative humidity affect comfort?
The relative humidity of the air affects how rapidly perspiration can
evaporate form the skin and cool the body. High humidity levels slow
evaporation and reduce body cooling.
41-4) How is the air volume affected by temperature?
Air volume increases as the air temperature increases.
41-5) What is the relationship between air volume and air weight (density)?
The volume and weight are affected oppositely. Increases in temperature
increase the volume and decrease the weight, while decreases in
temperature decrease the volume and increase the weight.
41-6) What are grains and what air property is measured in grains?
A grain is a small measurement of weight. 7000 grains = 1 pound. Grains
are used to measure the amount of water in the air. This is called the
specific humidity.
41-7) In general, which is heavier humid air or dry air?
Humid air lighter than dry air because water vapor is less dense than air.
41-8) What is a wet bulb temperature reading?
The wet bulb temperature is measured by placing a wick soaked with
water around the thermometer bulb and moving it rapidly through the air.
Water evaporates from the wick, cooling the bulb and lowering the
temperature.
41-9) How is relative humidity measured?
Wet bulb and dry bulb temperature readings are obtained with a sling
psychrometer and then compared to a wet bulb depression chart, a
relative humidity slide rule, or a psychrometric chart.
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41-10) What is the dew point temperature?
The dew point temperature is the temperature where water vapor can
begin condensing out of the air.
41-11) What is the difference between specific humidity and relative humidity?
Specific humidity is the actual weight of the water in each pound of dry
air, measured in grains. Relative humidity compares the amount of water
in the air to the amount of water the air can hold at a given temperature.
41-12) What is a psychrometric chart?
The psychrometric chart is a graphical representation of air properties.
41-13) List the air properties that are plotted on a psychrometric chart and give a brief
description of each.
Dry bulb temperature – the normal air temperature in degrees Fahrenheit
Wet bulb temperature – the temperature of a thermometer with a wet bulb
in degrees Fahrenheit. The wet bulb temperature reading takes the
moisture in the air into account.
Enthalpy – Measures the total heat content of the air in BTUs per pound
of air. Dew point temperature - Measures the temperature where water
will start to condense out of the air.
Specific Humidity – Measures the weight of water vapor in the air in
grains Relative humidity – Expresses the percentage of water vapor in the
air compared to the amount of water vapor the air can hold.
Specific volume – Measures the space in cubic feet occupied by each
pound of air. [Show Less]