A.Shortage of refrigerant oil
B.Slight shortage of refrigerant
C.Excessive condenser cooling water flow
D.Faulty expansion valve
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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
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
最新試題
Heavy wear in a particular area of the inner circumference of a packing ring may be caused by （）.
Thermostatic expansion valves can be adjusted for （）.
If the head pressure of a reciprocating refrigeration compressor is excessive, （）.
The rate of heat transfer between the hot and cold fluids passing through a shell-and-tube type heat exchanger will （）.
A salinity indicator is used to determine the （）.
A salinity indicator is used to determine the （）.
The major source of chemical contaminants in hydraulic fluid is （）.
When a refrigeration compressor has developed a high head pressure as a result of a refrigerant overcharge, you should （）.
If the relief valve on the discharge side of a hydraulic pump lifts, the cause could be （）.
If the viscosity of the liquid being transferred remains constant as the discharge pressure increases, the rotary pump （）.