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单选题
Air compressors are equipped with unloading systems for the purpose of（）.
A
removing all but the frictional load during starting
B
relieving intercoolers of high temperature buildups
C
providing high starting torque in the drive motor
D
seating valve plates during compressor shutdown
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Compressed air is supplied by air compressors to______.A.the air receiversB.the starting valvesC.the cylinder coversD.the distributors
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单选题Hot gas defrosting uses the hot gas from （） to defrost the evaporator.A
starting air bottlesB
diesel enginesC
boilersD
refrigeration compressors
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单选题By far the greatest use is for diesel engine starting using air pressure of 25 bar or more provided by （）.A
rotary compressorsB
reciprocating compressorsC
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单选题The unloading system on an air compressor will （）.A
increase compressor discharge pressure on demandB
increase compressor operating speed as necessaryC
allow the motor to turn the compressor opposed only by frictionD
reduce the compressor frictional load when starting
考题
单选题请阅读 Passage 1，完成第 21~25小题。Passage 1These days，many large city buildings are equipped with their own air-conditioning systems.These systems help keep the buildings cool，but they can also damage the environment.Since they use a lot of electricity，for instance，they contribute indirectly to global warming.In addition，the water that flows through the systems is often cooled using chemicals called chlorofluorocarbons，or CFCs，that are believed to damage the Earth's ozone layer.Recently，though，a system has been built in the city of Toronto，Canada，that cools buildings with little damage to the environment. In the traditional air-conditioning systems found in most large buildings，water is pumped through the building in a continuous cycle.The water is first cooled to a temperature of 4℃ in machines called chillers.It is then sent to individual units that cool the air in each room.As the water flows through the building，it gradually becomes warmer.Finally，it reaches the roof ，where it is left to cool down naturally in a water tower.After that it is returned to the chillers，where the cycle begins again.Toronto lies on the shore of Lake Ontario，one of North America's Great Lakes，and the new system makes use of cold water taken from about 80 meters below the surface of the lake.At this depth，the water in the lake remains at 4℃ all year round.This is exactly the temperature to which the water in air-conditioning systems is cooled.However，the water from the lake is not pumped directly into the air-conditioning systems.Instead，it is used to cool the water that is already inside the air-conditioning systems.After that，the lake water is added to the city's ordinary water supply.Enwave，the company that developed this deep-lake cooling system，says that it uses 75 percent less energy than traditional air conditioning.And since no CFCs are used，no damage can be caused to the ozone layer.Not every city is located next to a large lake，but experts believe that systems like the one being used in Toronto could be built elsewhere by using other natural sources of cold water.What is the function of the chillers in a traditional air-conditioning system?A
They pump the air continuously to the units in each room.B
They lower the temperature of the water in the system.C
They help the water cool down naturally on the roof .D
They gradually clean the water as it flows through the building.
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Vessel's typeB
Vessel's courseC
Navigational statusD
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单选题Intercoolers installed on starting air compressors, reduce the possibility of（）A
dust entering the high pressure stageB
lube oil carbonizationC
discharge pulsationsD
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单选题In the operation of a flash type evaporator equipped with air ejectors,the air and non- condensable gases are evacuated directly from the （）.A
first stage flash chamberB
second stage flash chamberC
first stage after condenserD
second stage distilling condenser
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单选题Which of the following statements is true concerning the overall efficiency of air compressors?（）A
High pressure compressors are more efficient than low pressure compressorsB
Mechanical efficiency divided by compressor efficiency will equal the overall efficiency of the compressor unitC
Two stage compressors are generally more efficient than single stage compressorsD
The volumetric efficiency is decreased in multistage compressors
考题
单选题On small, low pressure, air compressors, the cylinders are usually lubricated by the （）.A
splash methodB
mechanical force feed lubricatorsC
detached sump methodD
internal cooling passages in the crankshafts and connecting rods
考题
单选题Air line lubricators are used in compressed air systems to lubricate （）.A
the suction and discharge valvesB
tools and equipment served by compressed airC
air line reducing valvesD
all of the above
考题
单选题In order to distribute the side pressures over a wide area of the cylinder walls and liners, which of the listed types of pistons are used in modem low pressure air compressors?（）A
DifferentialB
TrunkC
BarrelD
Valve-in-head
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单选题With ducted air conditioning systems, the modern tendency is to use（）A
central air conditioning systemB
high velocity systemC
low velocity systemD
single duct system
考题
单选题The purpose of an air compressor unloading device is to （）A
drain water from the air receiverB
drain water from the cylindersC
delay the compression process until the motor is up to speedD
check pump alignment
考题
单选题An un-loader is installed on an air compressor to （）.A
bypass the high pressure stage to the low pressure stage on 100% of the air compressors in serviceB
prevent excessive inter-stage pressure buildupC
control compressor discharge pressureD
remove all but the frictional load during starting
考题
单选题Which of the following problems should be taken when cleaning the air filter on a diesel engine equipped with a turbocharger?（）A
Reduce engine speed to idle before removing the filterB
Soak the dirty filter in kerosene onlyC
Blow out the air inlet with compressed airD
Cover the air inlet after removing the filter
考题
单选题请阅读 Passage 1，完成第 21~25小题。Passage 1These days，many large city buildings are equipped with their own air-conditioning systems.These systems help keep the buildings cool，but they can also damage the environment.Since they use a lot of electricity，for instance，they contribute indirectly to global warming.In addition，the water that flows through the systems is often cooled using chemicals called chlorofluorocarbons，or CFCs，that are believed to damage the Earth's ozone layer.Recently，though，a system has been built in the city of Toronto，Canada，that cools buildings with little damage to the environment. In the traditional air-conditioning systems found in most large buildings，water is pumped through the building in a continuous cycle.The water is first cooled to a temperature of 4℃ in machines called chillers.It is then sent to individual units that cool the air in each room.As the water flows through the building，it gradually becomes warmer.Finally，it reaches the roof ，where it is left to cool down naturally in a water tower.After that it is returned to the chillers，where the cycle begins again.Toronto lies on the shore of Lake Ontario，one of North America's Great Lakes，and the new system makes use of cold water taken from about 80 meters below the surface of the lake.At this depth，the water in the lake remains at 4℃ all year round.This is exactly the temperature to which the water in air-conditioning systems is cooled.However，the water from the lake is not pumped directly into the air-conditioning systems.Instead，it is used to cool the water that is already inside the air-conditioning systems.After that，the lake water is added to the city's ordinary water supply.Enwave，the company that developed this deep-lake cooling system，says that it uses 75 percent less energy than traditional air conditioning.And since no CFCs are used，no damage can be caused to the ozone layer.Not every city is located next to a large lake，but experts believe that systems like the one being used in Toronto could be built elsewhere by using other natural sources of cold water.What happens in the end to the water from Lake Ontario?A
It is used by the residents of Toronto.B
It is returned to a place deep in the lake.C
It is cooled down before being used again.D
It is added to the water inside air-conditioning systems.
考题
单选题Air compressors are NOT permitted in which space(s) on a tank barge carrying grade A cargo?（）A
A cargo handling roomB
A space in which cargo hose is storedC
An enclosed space containing cargo pipingD
All of the above
考题
单选题Bad valves operation of the reciprocating air compressors can be detected by observation of （）.A
the discharge temperature lowB
the discharge temperature highC
the discharge pressure riseD
the inter-stage pressure low
考题
单选题Adequate attention must be given to the water cooling system of the air compressors, for （） can cause condensation on the cylinder walls.A
overcoolingB
poor coolingC
overloadingD
unloading
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Explosions do occur （） caused by the ignition of oil or vapour gaining access from compressors or defective engine starting valves.A
in boiler drumsB
in refrigerating plantsC
in starting air pipesD
in air coolers
考题
单选题请阅读 Passage 1，完成第 21~25小题。Passage 1These days，many large city buildings are equipped with their own air-conditioning systems.These systems help keep the buildings cool，but they can also damage the environment.Since they use a lot of electricity，for instance，they contribute indirectly to global warming.In addition，the water that flows through the systems is often cooled using chemicals called chlorofluorocarbons，or CFCs，that are believed to damage the Earth's ozone layer.Recently，though，a system has been built in the city of Toronto，Canada，that cools buildings with little damage to the environment. In the traditional air-conditioning systems found in most large buildings，water is pumped through the building in a continuous cycle.The water is first cooled to a temperature of 4℃ in machines called chillers.It is then sent to individual units that cool the air in each room.As the water flows through the building，it gradually becomes warmer.Finally，it reaches the roof ，where it is left to cool down naturally in a water tower.After that it is returned to the chillers，where the cycle begins again.Toronto lies on the shore of Lake Ontario，one of North America's Great Lakes，and the new system makes use of cold water taken from about 80 meters below the surface of the lake.At this depth，the water in the lake remains at 4℃ all year round.This is exactly the temperature to which the water in air-conditioning systems is cooled.However，the water from the lake is not pumped directly into the air-conditioning systems.Instead，it is used to cool the water that is already inside the air-conditioning systems.After that，the lake water is added to the city's ordinary water supply.Enwave，the company that developed this deep-lake cooling system，says that it uses 75 percent less energy than traditional air conditioning.And since no CFCs are used，no damage can be caused to the ozone layer.Not every city is located next to a large lake，but experts believe that systems like the one being used in Toronto could be built elsewhere by using other natural sources of cold water.What is one advantage of Enwave 's new system?A
It keeps buildings much cooler than other methods.B
It can be used by large cities anywhere in the world.C
It is much more energy-efficient than traditional systems.D
It keeps water from being used for more than one purpose.
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