A.Reduction of friction
B.Insulation of hot surfaces
C.Lubrication of moving parts
D.Elevation of cooler outlet temperatures
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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
A.the suction pressure to decrease
B.the suction temperature to increase
C.increased ice formation on the evaporator coil
D.excessive short cycling of the compressor
最新試題
Pitting in the suction areas of a centrifugal pump bronze impeller is usually caused by （）.
If the viscosity of the liquid being transferred remains constant as the discharge pressure increases, the rotary pump （）.
The control mode in which the final control element is moved from one of two flexed positions to the other is known as （）.
The usual symptoms of cavitation in a centrifugal pump is （）.
The output volume of a positive fixed displacement pump can be changed only by （）.
On tank vessels equipped with power operated cargo tank valves, the type of power operator most commonly used is （）.
A grease gun is generally used to lubricate a （）.
When a refrigeration compressor has developed a high head pressure as a result of a refrigerant overcharge, you should （）.
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（）.