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单选题
The amount of moisture in a given sample of air, when compared with the amount of moisture the air could hold if totally saturated at the existing temperature of the sample, is called （）.
A
absolute humidity
B
specific humidity
C
effective humidity
D
relative humidity
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As the amount of moisture in the air increases, the difference between the dry bulb and wet bulb temperatures will ______.A.increaseB.decreaseC.remain unchangedD.be greatest at dew point
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The moisture equilibrium chart can be used to determine the ______．A.Absolute moisture content of the air surrounding a hygroscopic cargo when moisture equilibrium existsB.Dew point temperature that the air surrounding a hygroscopic commodity will have when in moisture equilibrium with that commodityC.Enthalpy of the air surrounding a hydroscopic cargo which is in moisture equilibrium with the cargoD.Temperature at which moisture equilibrium will occur in a cargo hold containing a hygroscopic cargo
考题
单选题Some refrigeration systems have chemical moisture indicators installed in conjunction with the sight glass in the liquid lineIf excess moisture is present in the system, the indicator will （）A
activate the driersB
change colorC
secure the compressorD
add a predetermined amount of liquid drier
考题
单选题As the amount of moisture in the air increases, the difference between the dry bulb and wet bulb temperature will （）.A
increaseB
decreaseC
remain unchangedD
be greatest at dew point
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单选题If the moisture content of the cargo sample is（）the Transportable Moisture Limit,then the cargo should be safe to load.A
aboveB
belowC
equal toD
uncertain
考题
单选题When used in conjunction with a turbocharger, the main function of an after-cooler is to （）A
increase the density of the cylinder air chargeB
prevent turbocharger overheatingC
liminate the need for a pre-coolerD
remove moisture from air compressed by the turbocharger
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单选题Vapor given off by a flammable liquid will burn when ignited provided（）A
the vapor and air mixture is too richB
it is mixed with certain proportions of airC
the vapor is too little compared to the airD
it is of heavy toxicity
考题
单选题In an air conditioning system, moisture is removed from the air by（）A
filersB
separatorsC
ducted trapsD
dehumidifiers
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单选题Temperature and moisture characteristics are modified in a warm or cold air mass due to （）.A
pressure changes in the air massB
movement of the air massC
the heterogeneous nature of the air massD
upper level atmospheric changes
考题
单选题As the air passes through the charge air cooler, its temperature may be reduced and moisture condensed, with the condensate in danger of being carried into the engineSo a water separator should be mounted beneath the bottom part of the engine inlet manifoldA water separator is used in order to （）.A
keep the air from being carried into the engineB
keep the moisture from being condensedC
keep the danger from being carded into the engineD
take away the condensate from the air
考题
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 would the available energy of the exhaust gases of a two-stroke/cycle diesel engine be insufficient to drive an exhaust gas turbocharger, resulting in the incorrect amount of air for combustion?（）A
During operation at low speedB
During operation at rated speed, but low power outputC
During accelerationD
All of the above
考题
单选题Increasing the moisture content of conditioned air is known as （）.A
moisturizingB
dehumidificationC
dampeningD
humidification
考题
单选题In reference to air conditioning, when air attains the maximum amount of moisture it can hold at a specific temperature, it is said to be （）.A
superheatedB
saturatedC
condensedD
convected
考题
单选题The moisture equilibrium chart can be used to determine the（）.A
Absolute moisture content of the air surrounding a hygroscopic cargo when moisture equilibrium existsB
Dew point temperature that the air surrounding a hygroscopic commodity will have when in moisture equilibrium with that commodityC
Enthalpy of the air surrounding a hydroscopic cargo which is in moisture equilibrium with the cargoD
Temperature at which moisture equilibrium will occur in a cargo hold containing a hygroscopic cargo
考题
单选题The ratio of the weight of moisture contained in a given volume of air, to the weight of moisture that the same sample would hold if saturated, is called the（）.A
absolute humidityB
relative humidityC
specific humidityD
total humidity
考题
单选题When the load is increased on a turbocharged diesel engine, the amount of increased air supplied by the turbocharger will（）A
lag behind the increased fuel supplied to the engineB
enter the engine along with the increase in the fuelC
enter the engine before the increased fuel supplyD
leave the turbocharger as a negative pulse
考题
单选题Which of the processes listed would be the most satisfactory method to use to lower the humidity of the air being circulated by an air conditioning system?（）A
Cooling the air to a temperature just above dew pointB
Heating the air to a point at which moisture will boil off ,then re-cooling itC
Cooling the air to a point below dew point, then reheating itD
Heating the air and then cooling it to a point below dew point
考题
单选题By far the greatest item of maintenance of the reciprocating air compressors concerns （）.A
the lubricationB
the coolingC
the moisture separationD
the valves
考题
单选题Hot air can hold（）.A
less moisture than cold airB
more moisture than cold airC
the same amount of moisture as cold airD
moisture independent of air temperature
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