A.evaporatorB.compressorC.expansion valveD.condenserIn ……

单项选择题Excessive oil foaming in the crankcase of a refrigeration compressor is most likely to occur（） when the compressor.

A.has continuously for a long period
B.suction pressure is below normal
C.oil level is below normal
D.starts after a long idle period

单项选择题Strainers are commonly used in hydraulic systems to （）.

A.protect the pump from fine soluble contaminants
B.prevent solid particles from entering the pump
C.prevent solid particles from entering the filter
D.protect the directional control valves

单项选择题On which of the following heated surfaces of a flash type evaporator would you be more likely to find soft scale formation?（）

A.Feed-water heater internal tube surfaces
B.Internal distillate cooler tubes
C.Flash chamber vertical surfaces
D.Distilling condenser tubes

单项选择题Machinery operating features are designed to help conserve energy.Which of the following results will not contribute to energy conservation?（）

A.Reduction of friction
B.Insulation of hot surfaces
C.Lubrication of moving parts
D.Elevation of cooler outlet temperatures

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