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
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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
A.molecular fluid vibration
B.energy losses
C.wide pressure variations
D.mechanical damage to control valves
A.Keeps the refrigerated space cooler
B.Reduces the efficiency of the plant
C.Takes the load off the compressor
D.Has no affect on the system
最新試題
If the relief valve on the discharge side of a hydraulic pump lifts, the cause could be （）.
An increasing head pressure in a refrigeration system, without any corresponding change in the cooling water inlet temperature, would probably be caused by （）.
Who is responsible for ensuring that someone is assigned to close the watertight doors in an emergency?（）
If the suction pressure at the refrigeration compressor is below normal, the cause can be（）.
When a refrigeration compressor has developed a high head pressure as a result of a refrigerant overcharge, you should （）.
One cause of high head pressure occurring in a refrigeration system can be （）.
Which of the problems listed would came the discharge temperature of an R-12 refrigeration compressor to increase?（）
The rate of heat transfer between the hot and cold fluids passing through a shell-and-tube type heat exchanger will （）.
The output volume of a positive fixed displacement pump can be changed only by （）.
When the steering gear is in operation, you should （）.