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
The temperature differential occurring between the inlet temperature of the fluid to be cooled and the outlet temperature of the cooling medium in a shell-and-tube heat exchanger is greatest in which of the flow designs listed?（）
On tank vessels equipped with power operated cargo tank valves, the type of power operator most commonly used is （）.
Pitting in the suction areas of a centrifugal pump bronze impeller is usually caused by （）.
Which of the listed pumps is NOT a positive displacement pump?（）
An internal bypass is provided on some hydraulic system suction strainers to help reduce the possibility of （）.
The control mode in which the final control element is moved from one of two flexed positions to the other is known as （）.
If the suction pressure at the refrigeration compressor is below normal, the cause can be（）.
The amount of fluid friction or internal friction inherent in a mineral lubricating oil is reflected as a measure of its （）.
If you are given the job of adding hydraulic fluid to a mooring winch, and are not certain as to the type of fluid to use, you should （）.
When the steering gear is in operation, you should （）.