Which of the problems listed represent...

单项选择题Which of the problems listed represents the major difficulty encountered with thermal expansion valve operation?（）

A.Lube oil passing through the system
B.Moisture or foreign matter collecting at the valve seat and orifice
C.Variable spring tension caused by the changing temperature
D.Frost on the liquid line

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1.单项选择题Broken valve strips in an operating low pressure, air compressor will cause （）.

A.an immediate crankcase explosion
B.oil contamination in the compressed air
C.a decrease in compressor capacity
D.no immediate loss of the compressed air capacity

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2.单项选择题Which of the listed operating conditions would have the greatest effect on the volumetric efficiency of an operating reciprocating air compressor?（）

A.The density of the air entering the compressor
B.The temperature of the air entering the compressor
C.The designed rotating speed of the compressor
D.A leaking head gasket

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3.单项选择题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.Differential
B.Trunk
C.Barrel
D.Valve-in-head

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4.单项选择题A cracked diaphragm in a thermostatic expansion valve will cause the valve to （）.

A.return to a neutral position
B.flood the evaporator
C.open
D.close

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5.单项选择题If an air compressor is used to supply air primarily to the combustion control system and other pneumatic controllers, the entire system is known as the （）.

A.control air system
B.forced draft air system
C.supply air system
D.ships service air system

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6.单项选择题When it is necessary to open a refrigeration system for repairs and the system will be open for more than a few minutes, the open ends of the system should be （）.

A.dehydrated
B.purged
C.plugged
D.evacuated

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7.单项选择题If an air compressor is used to supply compressed air to outlets throughout the engine room and on deck of a vessel, the system is known as the （）.

A.combustion control air system
B.supply air system
C.ships service air system
D.low pressure deck air system

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8.单项选择题The sensible heat of air is dependent upon the （）.

A.dry bulb temperature
B.wet bulb temperature
C.saturation temperature
D.water vapor superheat

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9.单项选择题Which of the devices listed, when used on an electro-hydraulic steering gear, keeps the movement of the redder closely in step with the steering wheel?（）

A.The follow-up gear
B.The rudder angle indicator
C.The synchronous electric transmitter
D.A rudder angle limit switch

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10.单项选择题Propeller pitch speed minus ship speed divided by the propeller pitch speed is termed （）.

A.apparent slip
B.tree slip
C.pitch
D.propulsive efficiency

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