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
您可能感兴趣的试卷
你可能感兴趣的试题
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
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
A.a shortage of compressor oil
B.warm food in the refrigerator
C.excessive condenser cooling water
D.a shortage of refrigerant
最新试题
A gradual decrease in the discharge pressure of an operating hydraulic pump can be caused by ().
Which of the listed pumps is NOT a positive displacement pump?()
Who is responsible for ensuring that someone is assigned to close the watertight doors in an emergency?()
The output volume of a positive fixed displacement pump can be changed only by ().
If the suction pressure at the refrigeration compressor is below normal, the cause can be().
Which of the problems listed would came the discharge temperature of an R-12 refrigeration compressor to increase?()
Which of the following statements is correct concerning heat transfer?()
When a refrigeration compressor has developed a high head pressure as a result of a refrigerant overcharge, 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 ().
Thermostatic expansion valves can be adjusted for ().