A.Hydraulic
B.Mechanical
C.Pneumatic
D.Electrical
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A.Energy can be created or destroyed
B.Energy may not be transformed
C.The total quantity of energy in the universe is always the same
D.None of the above
A.evaporator
B.compressor
C.expansion valve
D.condenser
A.has continuously for a long period
B.suction pressure is below normal
C.oil level is below normal
D.starts after a long idle period
A.protect the pump from fine soluble contaminants
B.prevent solid particles from entering the pump
C.prevent solid particles from entering the filter
D.protect the directional control valves
A.Feed-water heater internal tube surfaces
B.Internal distillate cooler tubes
C.Flash chamber vertical surfaces
D.Distilling condenser tubes
A.Reduction of friction
B.Insulation of hot surfaces
C.Lubrication of moving parts
D.Elevation of cooler outlet temperatures
A.higher boiling temperature for a given pressure than does a pure refrigerant
B.lower boiling temperature for a given pressure than does a pure refrigerant
C.boiling pressure equal to that of a pure refrigerant at a given pressure
D.boiling point will not be affected by entrained oil
A.Degree of saturation
B.Saturation temperature
C.Superheated temperature
D.Degree of superheat
A.pump must always be primed
B.volute must impart a radial and rotary motion of the water suction side
C.connection must guide the liquid to the lantern rings
D.stuffing box should not be allowed any water leakage
A.change in impeller diameter
B.square of the impeller diameter
C.cube of the impeller diameter
D.impeller efficiency for large changes in the size of the impeller
最新试题
If the relief valve on the discharge side of a hydraulic pump lifts, the cause could be （）.
If the suction pressure at the refrigeration compressor is below normal, the cause can be（）.
A gradual decrease in the discharge pressure of an operating hydraulic pump can be caused by （）.
Which of the following problems could cause the high pressure cutout switch to shut down the compressor in a refrigeration system?（）
Low compressor head pressure in a refrigeration system can be caused by（）.
A grease gun is generally used to lubricate a （）.
Which of the listed pumps is NOT a positive displacement pump?（）
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 （）.
The usual symptoms of cavitation in a centrifugal pump is （）.