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
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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 （）.
The major source of chemical contaminants in hydraulic fluid is （）.
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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?（）
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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 from a hot region to a cold region is affected most by the （）.
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