A.providing the impeller with balancing holes
B.the use of symmetrical impeller
C.neither A nor B
D.either A or B
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A.throttling the pressure line
B.changing the speed of the rotor
C.either A or B
D.None of the above is true
Which of the following pumps are self-priming, and can deal with liquid from a level below the pump（）
(1) ejector
(2) screw
(3) centrifugal
A.(1)only
B.(1)and(2)
C.(1),(2)and(3)
D.(2)and(3)
A.centrifugal
B.plunger
C.injector
D.water
A.discharges into a gradually widening channel
B.has stationary diffuser vanes
C.produces no kinetic energy
D.All of the above are true
A.Piston pump
B.Screw pump
C.Diffuser pump
D.Water-ring pump
最新試題
Which of the following statements is correct concerning heat transfer?（）
When a refrigeration compressor has developed a high head pressure as a result of a refrigerant overcharge, you should （）.
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?（）
The usual symptoms of cavitation in a centrifugal pump is （）.
An excessive charge of refrigerant in an air-cooled refrigeration system can cause （）.
One cause of high head pressure occurring in a refrigeration system can be （）.
A grease gun is generally used to lubricate a （）.
Thermostatic expansion valves can be adjusted for （）.
Which of the following problems could cause the high pressure cutout switch to shut down the compressor in a refrigeration system?（）
If you are given the job of adding hydraulic fluid to a mooring winch, and are not certain as to the type of fluid to use, you should （）.