A.increased；decreased
B.decreased；increased
C.decreased；decreased
D.increased；increased
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A.kg
B.MPa
C.mH20
D.None of the above
Which of the following are components of a mechanical seal? （）
(1) stationary ring
(2) rotational ring
(3) packing
(4)spring
A.(1), (2) and (3)
B.(1), (2) and (4)
C.(2), (3) and (4)
D.None of the above
A.variable stroke pumps
B.multistage pumps
C.positive displacement pumps
D.triple-ported pumps
A.mixed-flow pump
B.axial-flow pump
C.centrifugal pump
D.displacement pump
A.on top cover
B.on sides of bowl
C.in drain line on the discs
D.on the discs
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 （）.
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?（）
One cause of high head pressure occurring in a refrigeration system can be （）.
The general purpose of a heat exchanger is to （）.
Thermostatic expansion valves can be adjusted for （）.
If the head pressure of a reciprocating refrigeration compressor is excessive, （）.
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?（）
Heavy wear in a particular area of the inner circumference of a packing ring may be caused by （）.
The output volume of a positive fixed displacement pump can be changed only by （）.