A.reduce
B.rise
C.raise
D.fall
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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
A.Volute pump
B.Diffuser pump
C.Regenerative pump
D.All of the above
A.mixed-flow
B.axial-flow
C.centrifugal
D.displacement
Which of the following operating features do displacement pumps bear if they are working under no-cavitation condition?（）
(1) output is almost directly proportional to speed
(2) they are self-priming
(3) they will develop a discharged pressure equal to the resistance to be overcome, irrespective of speed
A.（1）and（2）
B.（2）and（3）
C.（1）and（3）
D.（1），（2）and（3）
最新試題
An increasing head pressure in a refrigeration system, without any corresponding change in the cooling water inlet temperature, would probably be caused by （）.
A gradual decrease in the discharge pressure of an operating hydraulic pump can be caused by （）.
Which of the following problems could cause the high pressure cutout switch to shut down the compressor in a refrigeration system?（）
If the suction pressure at the refrigeration compressor is below normal, the cause can be（）.
The output volume of a positive fixed displacement pump can be changed only by （）.
If the head pressure of a reciprocating refrigeration compressor is excessive, （）.
Which of the following statements is correct concerning heat transfer?（）
Heavy wear in a particular area of the inner circumference of a packing ring may be caused by （）.
One cause of high head pressure occurring in a refrigeration system can be （）.
Which of the problems listed would came the discharge temperature of an R-12 refrigeration compressor to increase?（）