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
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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
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The rate of heat transfer from a hot region to a cold region is affected most by the （）.
A salinity indicator is used to determine the （）.
The temperature differential occurring between the inlet temperature of the fluid to be cooled and the outlet temperature of the cooling medium in a shell-and-tube heat exchanger is greatest in which of the flow designs listed?（）
An excessive charge of refrigerant in an air-cooled refrigeration system can cause （）.
If the relief valve on the discharge side of a hydraulic pump lifts, the cause could be （）.
The major source of chemical contaminants in hydraulic fluid is （）.
Pitting in the suction areas of a centrifugal pump bronze impeller is usually caused by （）.
If the head pressure of a reciprocating refrigeration compressor is excessive, （）.
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（）.