A.injector pumps
B.positive displacement pumps
C.centrifugal pump
D.centripetal pumps
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A.the mechanical seal
B.packed stuffing boxes
C.either A or B
D.neither A nor B
As for a hydraulic vane pump, which of the following is in contact with the vanes during working: （）
(1)the rotor
(2)the pump shaft
(3)the external surface of the housing
A.(1) only
B.(2) only
C.(1) and (2)
D.(1),(2)and(3)
A.circular
B.elliptical
C.rectangular
D.hexagon
A.suction
B.exhaust
C.pressure
D.discharge
A.draw the liquid in；force the liquid out
B.force the liquid out；draw the liquid in
C.suction；draw
D.deliver；outlet
A.throttling the pressure line
B.changing the speed of the rotor
C.either A or B
D.None of the above is tree
Which of the following pumps are self-priming, and can deal with liquid from a level below the pump? （）
(1) reciprocating
(2) rotary
(3) centrifugal
A.(1)only
B.(1)and (2)
C.(1),(2)and(3)
D.(2)and(3)
A.throttling the pressure line
B.changing the speed of the driving rotor
C.either A or B
D.None of the above is tree
A.throttling the pressure line
B.changing the speed of the piston
C.either A or B
D.None of the above is tree
A.throttling the pressure line
B.changing the speed of the rotor
C.either A or B
D.None of the above is tree
最新试题
An increasing head pressure in a refrigeration system, without any corresponding change in the cooling water inlet temperature, would probably be caused by （）.
The output volume of a positive fixed displacement pump can be changed only by （）.
An excessive charge of refrigerant in an air-cooled refrigeration system can cause （）.
An internal bypass is provided on some hydraulic system suction strainers to help reduce the possibility of （）.
A salinity indicator is used to determine the （）.
If the relief valve on the discharge side of a hydraulic pump lifts, the cause could be （）.
The rate of heat transfer between the hot and cold fluids passing through a shell-and-tube type heat exchanger will （）.
Which of the following statements is correct concerning heat transfer?（）
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?（）