A.in series
B.in parallel
C.either A or B
D.None of the above is tree
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Which of the following pumps are self-priming, and can deal with liquid from a level below the pump: （）
(1)reciprocating
(2)vane
(3)gear
A.（1）only
B.（1）and（2）
C.（2）and（3）
D.（1），（2）and（3）
Which of the following will be the advantage of a centrifugal pump as compared with a reciprocating pump?（）
(1) Its discharge is continuous
(2) It has no internal valves
(3) Upon accidental closing of discharge valve, excessive pressure will not build up
A.（1），（2）
B.（2），（3）
C.（1），（2），（3）
D.（2）only
A.reduce
B.rise
C.raise
D.fall
A.increase discharge pressure
B.increase suction vacuum
C.develop pulsation flow
D.keep a steady rate of flow
A.slack enough to allow slight leakage of fluid
B.slightly clocked
C.brought up tight so as not to allow any leakage
D.fitted with a relief valve
最新試題
Which of the following statements is correct concerning heat transfer?（）
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 rate of heat transfer between the hot and cold fluids passing through a shell-and-tube type heat exchanger will （）.
An increasing head pressure in a refrigeration system, without any corresponding change in the cooling water inlet temperature, would probably be caused by （）.
The major source of chemical contaminants in hydraulic fluid is （）.
The usual symptoms of cavitation in a centrifugal pump is （）.
The rate of heat transfer from a hot region to a cold region is affected most by the （）.
The control mode in which the final control element is moved from one of two flexed positions to the other is known as （）.
Which of the listed pumps is NOT a positive displacement pump?（）
A pressure drop through the refrigerant liquid line may cause （）.