A.excessive condenser cooling water
B.warm food in the refrigerator
C.a shortage of refrigerant
D.s shortage of compressor oil
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A.either all the way open or all the way closed
B.normally open
C.throttled depending on load
D.controlled by suction pressure
When a hydraulic vane pump is working, which of the following is in contact with the vanes?（）
(1) the rotor
(2) the internal surface of the housing
(3) the external surface of the housing
A.(1) only
B.(2) only
C.(1) and (2)
D.(1), (2) and (3)
A.Control of evaporation
B.A separate means to prevent feed-water contamination
C.Power circulating pump
D.Super-heater
A.check and regulate the water level
B.close the air cock once fires are lit
C.blowdown the gage glass
D.crack the steam stop to assure protective steam flow
A.furnace to be re-purged
B.electric charge to buildup in the igniter
C.fuel pump to restart
D.drum level to stabilize
最新試題
Heavy wear in a particular area of the inner circumference of a packing ring may be caused by （）.
Low compressor head pressure in a refrigeration system can be caused by（）.
The rate of heat transfer from a hot region to a cold region is affected most by the （）.
The general purpose of a heat exchanger is to （）.
When a refrigeration compressor has developed a high head pressure as a result of a refrigerant overcharge, you should （）.
If the thermal bulb of an expansion valve is incorrectly placed at the center of the coil instead of the end, it will （）.
Who is responsible for ensuring that someone is assigned to close the watertight doors in an emergency?（）
The amount of fluid friction or internal friction inherent in a mineral lubricating oil is reflected as a measure of its （）.
A salinity indicator is used to determine the （）.
An internal bypass is provided on some hydraulic system suction strainers to help reduce the possibility of （）.