A.Reduction of frictionB.Insulation of hot surfacesC.Lu……

单项选择题A refrigerant with oil in solution has a （）.

A.higher boiling temperature for a given pressure than does a pure refrigerant
B.lower boiling temperature for a given pressure than does a pure refrigerant
C.boiling pressure equal to that of a pure refrigerant at a given pressure
D.boiling point will not be affected by entrained oil

单项选择题Which of the following terms would best describe the temperature at which a liquid boils at a given pressure?（）

A.Degree of saturation
B.Saturation temperature
C.Superheated temperature
D.Degree of superheat

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