單項(xiàng)選擇題The gear, screw, and vane pumps are all classified as ().

A.variable stroke pumps
B.multistage pumps
C.positive displacement pumps
D.triple-ported pumps


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1.單項(xiàng)選擇題The () discharge a nearly constant amount of liquid regardless of pressure.

A.mixed-flow pump
B.axial-flow pump
C.centrifugal pump
D.displacement pump

2.單項(xiàng)選擇題Sediment collects in a tubular purifier ().

A.on top cover
B.on sides of bowl
C.in drain line on the discs
D.on the discs

4.單項(xiàng)選擇題In (), hot diesel engine jacket water passes over the stack and heats the sea water passing through the tubes.

A.a flash generator
B.a flash evaporator
C.a vacuum boiling evaporator
D.a boiler

5.單項(xiàng)選擇題When a boiler is operating, the water level in the gauge glass reads () when the boiler is shut down.

A.lower than
B.higher than
C.as much as
D.the same as