A.The two objects must be in physical contact
B.The two objects must be the same size
C.There must be an existing temperature differential
D.There must be an existing weight differential
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A.insufficient lubrication
B.insufficient refrigerant
C.excess refrigerant
D.excessive opening of the expansion valve
A.increase compressor discharge pressure on demand
B.increase compressor operating speed as necessary
C.allow the motor to turn the compressor opposed only by friction
D.reduce the compressor frictional load when starting
A.Radiation
B.Conduction
C.Convection
D.Each of the above
A.Shortage of refrigerant oil
B.Slight shortage of refrigerant
C.Excessive condenser cooling water flow
D.Faulty expansion valve
A.vary their speed according to temperature and load
B.start and come up to speed before air compression begins
C.change speed according to overload demands
D.reduce compressed air charge density
最新試題
The rate of heat transfer from a hot region to a cold region is affected most by the （）.
Low compressor head pressure in a refrigeration system can be caused by（）.
When a refrigeration compressor has developed a high head pressure as a result of a refrigerant overcharge, you should （）.
Which of the following problems could cause the high pressure cutout switch to shut down the compressor in a refrigeration system?（）
Who is responsible for ensuring that someone is assigned to close the watertight doors in an emergency?（）
The usual symptoms of cavitation in a centrifugal pump is （）.
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?（）
If the thermal bulb of an expansion valve is incorrectly placed at the center of the coil instead of the end, it will （）.
Thermostatic expansion valves can be adjusted for （）.
A gradual decrease in the discharge pressure of an operating hydraulic pump can be caused by （）.