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 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?（）
One cause of high head pressure occurring in a refrigeration system can be （）.
The usual symptoms of cavitation in a centrifugal pump 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 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 （）.
Low compressor head pressure in a refrigeration system can be caused by（）.
The rate of heat transfer between the hot and cold fluids passing through a shell-and-tube type heat exchanger will （）.
The general purpose of a heat exchanger is to （）.
An internal bypass is provided on some hydraulic system suction strainers to help reduce the possibility of （）.
Which of the following problems could cause the high pressure cutout switch to shut down the compressor in a refrigeration system?（）