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
A salinity indicator is used to determine the （）.
The control mode in which the final control element is moved from one of two flexed positions to the other is known as （）.
Pitting in the suction areas of a centrifugal pump bronze impeller is usually caused by （）.
A grease gun is generally used to lubricate a （）.
The amount of fluid friction or internal friction inherent in a mineral lubricating oil is reflected as a measure of its （）.
Which of the problems listed would came the discharge temperature of an R-12 refrigeration compressor to increase?（）
The usual symptoms of cavitation in a centrifugal pump is （）.
Thermostatic expansion valves can be adjusted for （）.
Which of the listed pumps is NOT a positive displacement pump?（）
Heavy wear in a particular area of the inner circumference of a packing ring may be caused by （）.