A.Degree of saturationB.Saturation temperatureC.Superhe……

单项选择题To thoroughly pump out the bilges using a horizontally mounted centrifugal pump, the （）.

A.pump must always be primed
B.volute must impart a radial and rotary motion of the water suction side
C.connection must guide the liquid to the lantern rings
D.stuffing box should not be allowed any water leakage

单项选择题The discharge head of a centrifugal pump will vary directly with the （）.

A.change in impeller diameter
B.square of the impeller diameter
C.cube of the impeller diameter
D.impeller efficiency for large changes in the size of the impeller

单项选择题An increase in the heat load to a refrigeration system will cause （）.

A.the suction pressure to decrease
B.the suction temperature to increase
C.increased ice formation on the evaporator coil
D.excessive short cycling of the compressor

单项选择题Which of the following types of hydraulic pumps would be used in a steering system?（）

A.Lobe
B.Screw
C.Radial piston
D.Volute

单项选择题Which of the following statements is true concerning centrifugal pumps?（）

A.They are particularly suited for pumping high viscosity fluids
B.They are started with the discharge valve opened
C.The flow of liquid is developed by imparting energy due to the rotation of an impeller
D.They are always mounted in a horizontal position