A.proportional band
B.the error signal
C.the reset signal
D.feedback
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A.Dehydrators must be used continuously in a refrigeration system
B.A 25 ton refrigeration system has the same cooling effect as melting 25 tons of ice in 24 hours
C.A thermostatic expansion valve is used to control refrigerated space temperature
D.The liquid receiver functions to collect and remove non- condensable gases
A.Hydraulic
B.Mechanical
C.Pneumatic
D.Electrical
A.Energy can be created or destroyed
B.Energy may not be transformed
C.The total quantity of energy in the universe is always the same
D.None of the above
A.evaporator
B.compressor
C.expansion valve
D.condenser
A.has continuously for a long period
B.suction pressure is below normal
C.oil level is below normal
D.starts after a long idle period
最新試題
Which of the following statements is correct concerning heat transfer?（）
A gradual decrease in the discharge pressure of an operating hydraulic pump can be caused by （）.
Who is responsible for ensuring that someone is assigned to close the watertight doors in an emergency?（）
If the head pressure of a reciprocating refrigeration compressor is excessive, （）.
The amount of fluid friction or internal friction inherent in a mineral lubricating oil is reflected as a measure of its （）.
If the viscosity of the liquid being transferred remains constant as the discharge pressure increases, the rotary pump （）.
The output volume of a positive fixed displacement pump can be changed only by （）.
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 （）.
A salinity indicator is used to determine the （）.
The major source of chemical contaminants in hydraulic fluid is （）.