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
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A.radiation
B.conduction
C.convection
D.condo-radiation
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
A.Radiation
B.Conduction
C.Natural convection
D.All of the above
A.A gate valve
B.A globe valve
C.Any check valve
D.Any needle valve
A.a shortage of compressor oil
B.warm food in the refrigerator
C.excessive condenser cooling water
D.a shortage of refrigerant
最新試題
Who is responsible for ensuring that someone is assigned to close the watertight doors in an emergency?（）
An excessive charge of refrigerant in an air-cooled refrigeration system can cause （）.
A grease gun is generally used to lubricate a （）.
Thermostatic expansion valves can be adjusted for （）.
Which of the listed pumps is NOT a positive displacement pump?（）
A salinity indicator is used to determine the （）.
The output volume of a positive fixed displacement pump can be changed only by （）.
A gradual decrease in the discharge pressure of an operating hydraulic pump can be caused by （）.
If the thermal bulb of an expansion valve is incorrectly placed at the center of the coil instead of the end, it will （）.
The usual symptoms of cavitation in a centrifugal pump is （）.