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单选题
Relative humidity is the percentage of water vapor that is in the air as compared to the maximum amount it can hold at（）.
A
a specific barometric pressure
B
a specific temperature
C
a specific wind speed
D
any time
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If air at 95°Cdry bulb temperature and 50%relative humidity is conditioned to 75°Cdry bulb temperature and 50%relative humidity, it is an example of()
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A hygrometer is device used for determining ______.A.the absolute temperatureB.atmospheric pressureC.wind velocityD.relative humidity
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As the temperature for an air mass decreases, the ______.A.absolute humidity increasesB.relative humidity increasesC.specific humidity increasesD.dew point rises
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As the temperature for a given mass of air increases, the ______.A.dew point increasesB.dew point decreasesC.relative humidity increasesD.relative humidity decreases
考题
单选题The expression THE AIR IS SATURATED means（）.A
the relative humidity is 100%B
the vapor pressure is at its minimum for the prevailing temperatureC
precipitation has commencedD
cloud cover is 100%
考题
单选题The dew point is reached when the（）.A
temperature of the air equals the temperature of the seawaterB
atmospheric pressure is 14.7 lbs. per square inchC
relative humidity reaches 50%D
air becomes saturated with water vapor
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单选题The temperature at which water vapor in the atmosphere begins to condense is called the （）.A
dew point temperatureB
condensation temperatureC
psychometric temperatureD
absolute humidity temperature
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单选题The temperature at which the air is saturated with water vapor and below which condensation of water vapor will occur is referred to as the（）.A
precipitation pointB
vapor pointC
dew pointD
absolute humidity
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单选题Clouds form（）.A
as a mass of warm，humid air rises into the atmosphere and cools，condensing moisture into small dropletsB
as winds blow across bodies of water，the sun causes the moisture to be absorbed and move upward forming cloudsC
dry air compresses moisture from the atmosphere into cloudsD
when the relative humidity of the atmosphere is low
考题
问答题Practice 1 Heat loss by sweating depends on the fact that when a liquid evaporates, it absorbs an enormous quantity of heat from its surroundings. Therefore, when I am of sweat evaporate, a great deal of heat is absorbed from the surface of the body in contact with it. 1______ 2______ The first is the amount of movement of air surrounding the body. The second is the amount of water vapor in the air that surrounds the body. 3______ For this reason, sweat evaporates very rapidly on windy days, and the rate of heat loss by sweating is much more than on a still day. This accounts for the fact that hot still days are much less comfortable than hot windy days. In contrast, the sweat evaporates very rapidly on hot windy days, and cools the body quickly and effectively. 4______ When air is carrying the maximum amount of water vapor that it can hold, it is said to be 100% saturated with water vapor. The relative humidity of the air is said to be 100%. Under these conditions the air cannot carry any water, so no water can evaporate. When the relative humidity is high, therefore, sweat cannot evaporate. Instead, it forms large drops and runs off your skin without cooling you. 5______ It is obvious that under these conditions, evaporation will be much more rapid. Therefore, sweating will be much more effective as a method of losing heat from the body. On a hot dry day, sweat evaporates as soon as it is formed, and you feel reasonably cool even though the temperature of your environment is very high.[A] When the air is very dry and carries no water at all, the relative humidity is said to be 0%.[B] The second factor is the amount of water vapor in the air－the humidity.[C] Hot windy days are much more comfortable than hot still days.[D] This heat transfer occurs even if the environment is hotter than the body.[E] When air moves over the surface of water, the amount of evaporation is greatly increased.[F] You might expect the highest incidence of a heat stroke when the maximum temperature is 100 and humidity is 50%.[G] Two factors affect the rate of evaporation of sweat, and therefore the effectiveness of sweating as a method of cooling the body.
考题
单选题When air is at its dew point it is at its（）A
lowest absolute humidityB
lowest relative humidityC
highest absolute humidityD
highest relative humidity
考题
单选题Which instrument is used to measure the relative humidity of air?（）A
HydrometerB
HygrometerC
SpectrometerD
Barometer
考题
单选题If air at 95℃ dry bulb temperature and 50% relative humidity is conditioned to 75℃ dry bulb temperature and 50% relative humidity, it is an example of （）.A
cooling onlyB
cooling and humidifyingC
cooling and dehumidifyingD
adiabatic cooling
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单选题A cargo hold has been determined to have a relative humidity of 80% and a dry bulb temperature of 80 ℃ and a dry bulb temperature of 85℃.When the hold is sealed and the dry bulb temperature decreases, the relative humidity in the space will （）A
decreaseB
increaseC
decrease to zeroD
remain unchanged
考题
单选题When comparing the air with 50% of relative humidity with the air with 100% of relative humidity, which one will hold more water?（）A
the formerB
the latterC
not for sureD
same each other
考题
单选题How dose water enter the crankcase of a diesel engine?（）A
Through the crankcase exhausterB
As water vapor contained in blow-byC
Demulsifying lube oil passing through the main bearingsD
Condensation from vapor formed in the expansion tank
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单选题A lower thermostatic temperature setting will provide a desired degree of comfort in a room where （）A
low relative humidity is maintainedB
triple banded squirrel cage fans are usedC
air circulation is a maximumD
high relative humidity is maintained
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单选题Which of the following statements is correct relative to distillation plant operation?（）A
Distillation is the process of boiling seawater to produce vapor which is condensed into fresh waterB
Evaporation is the second part of the distillation process where brine is removedC
Brine is the result of condensed sea water vaporD
Distillate is the product resulting from the evaporation of fresh water vapor
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