A.insufficient lubrication
B.insufficient refrigerant
C.excess refrigerant
D.excessive opening of the expansion valve
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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
A.radiation
B.conduction
C.convection
D.condo-radiation
最新試題
The usual symptoms of cavitation in a centrifugal pump is （）.
Low compressor head pressure in a refrigeration system can be caused by（）.
A gradual decrease in the discharge pressure of an operating hydraulic pump can be caused by （）.
If the relief valve on the discharge side of a hydraulic pump lifts, the cause could be （）.
Thermostatic expansion valves can be adjusted for （）.
If the suction pressure at the refrigeration compressor is below normal, the cause can be（）.
Which of the following problems could cause the high pressure cutout switch to shut down the compressor in a refrigeration system?（）
An excessive charge of refrigerant in an air-cooled refrigeration system can cause （）.
Which of the following statements is correct concerning heat transfer?（）
One cause of high head pressure occurring in a refrigeration system can be （）.