A.throttling the pressure line
B.changing the speed of the rotor
C.either A or B
D.None of the above is true
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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
A.pump entry branch
B.outlet pipe
C.impeller
D.None of the above is true
最新試題
Which of the problems listed would came the discharge temperature of an R-12 refrigeration compressor to increase?（）
Which of the following statements is correct concerning heat transfer?（）
If the viscosity of the liquid being transferred remains constant as the discharge pressure increases, the rotary pump （）.
Which of the following problems could cause the high pressure cutout switch to shut down the compressor in a refrigeration system?（）
The rate of heat transfer between the hot and cold fluids passing through a shell-and-tube type heat exchanger will （）.
When the steering gear is in operation, 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?（）
Low compressor head pressure in a refrigeration system can be caused by（）.
If the head pressure of a reciprocating refrigeration compressor is excessive, （）.
An increasing head pressure in a refrigeration system, without any corresponding change in the cooling water inlet temperature, would probably be caused by （）.