A.Radiation
B.Conduction
C.Natural convection
D.All of the above
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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
A.evaporator
B.compressor
C.expansion valve
D.condenser
A.has continuously for a long period
B.suction pressure is below normal
C.oil level is below normal
D.starts after a long idle period
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最新试题
When the steering gear is in operation, you should ().
The control mode in which the final control element is moved from one of two flexed positions to the other is known as ().
The amount of fluid friction or internal friction inherent in a mineral lubricating oil is reflected as a measure of its ().
On tank vessels equipped with power operated cargo tank valves, the type of power operator most commonly used is ().
If the thermal bulb of an expansion valve is incorrectly placed at the center of the coil instead of the end, it will ().
If the viscosity of the liquid being transferred remains constant as the discharge pressure increases, the rotary pump ().
A grease gun is generally used to lubricate a ().
One cause of high head pressure occurring in a refrigeration system can be ().
Low compressor head pressure in a refrigeration system can be caused by().
If the relief valve on the discharge side of a hydraulic pump lifts, the cause could be ().