A.Radiation
B.Conduction
C.Natural convection
D.All of the above
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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
A.molecular fluid vibration
B.energy losses
C.wide pressure variations
D.mechanical damage to control valves
A.Keeps the refrigerated space cooler
B.Reduces the efficiency of the plant
C.Takes the load off the compressor
D.Has no affect on the system
A.proportional band
B.the error signal
C.the reset signal
D.feedback
最新試題
The rate of heat transfer between the hot and cold fluids passing through a shell-and-tube type heat exchanger will （）.
Heavy wear in a particular area of the inner circumference of a packing ring may be caused by （）.
If the relief valve on the discharge side of a hydraulic pump lifts, the cause could be （）.
The amount of fluid friction or internal friction inherent in a mineral lubricating oil is reflected as a measure of its （）.
If the suction pressure at the refrigeration compressor is below normal, the cause can be（）.
The rate of heat transfer from a hot region to a cold region is affected most by the （）.
The major source of chemical contaminants in hydraulic fluid is （）.
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?（）
An internal bypass is provided on some hydraulic system suction strainers to help reduce the possibility of （）.