单项选择题
Which of the conditions listed will cause a refrigeration compressor to run constantly without simultaneously decreasing the temperature in the refrigerated space?（）
A.Shortage of refrigerant oil
B.Slight shortage of refrigerant
C.Excessive condenser cooling water flow
D.Faulty expansion valve
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相关考题
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单项选择题
Air compressor cylinder un-loaders enable the compressor to （）.
A.vary their speed according to temperature and load
B.start and come up to speed before air compression begins
C.change speed according to overload demands
D.reduce compressed air charge density -
单项选择题
The movement of heat within a fluid, caused by the application of thermal energy, is called （）.
A.radiation
B.conduction
C.convection
D.condo-radiation -
单项选择题
A gate valve installed in a pipeline should be （）.
A.used in either the fully dosed or fully opened position
B.installed with the stem down
C.used for steam service only
D.used to throttle or regulate the flow of liquid
