A.radiation
B.conduction
C.convection
D.condo-radiation
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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
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
A.proportional band
B.the error signal
C.the reset signal
D.feedback
A.Dehydrators must be used continuously in a refrigeration system
B.A 25 ton refrigeration system has the same cooling effect as melting 25 tons of ice in 24 hours
C.A thermostatic expansion valve is used to control refrigerated space temperature
D.The liquid receiver functions to collect and remove non- condensable gases
A.Hydraulic
B.Mechanical
C.Pneumatic
D.Electrical
A.Energy can be created or destroyed
B.Energy may not be transformed
C.The total quantity of energy in the universe is always the same
D.None of the above
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最新试题
Which of the following problems could cause the high pressure cutout switch to shut down the compressor in a refrigeration system?()
A pressure drop through the refrigerant liquid line may cause ().
Which of the listed pumps is NOT a positive displacement pump?()
Pitting in the suction areas of a centrifugal pump bronze impeller is usually caused by ().
The output volume of a positive fixed displacement pump can be changed only by ().
If the suction pressure at the refrigeration compressor is below normal, the cause can be().
A grease gun is generally used to lubricate a ().
The usual symptoms of cavitation in a centrifugal pump is ().
An excessive charge of refrigerant in an air-cooled refrigeration system can cause ().
Which of the following statements is correct concerning heat transfer?()