A.At the designed operating temperature, the liquid refrigerant charge has changed to a vapor
B.The liquid refrigerant tends to collect at the bellows or diaphragm and reduces the valve sensitivity
C.The sensing bulb is empty of liquid refrigerant charge at the designed operating temperature
D.The sensing bulb is never emptied of liquid refrigerant under normal operating conditions
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A.diaphragm type gage
B.pressure transducer
C.manometer
D.All of the above
A.reduce radial thrust to the impeller
B.double the liquid velocity through the pump when compared to a single volute
C.reduce hydraulic end thrust
D.provide the effect of multi-staging
A.dirt will cause corrosion of bearing
B.bearings will leak oil excessively
C.dirt is very abrasive when mixed with grease
D.grease will become inflammable
A.promote refrigerant dehydration
B.be absorbed in the receiver
C.cause low condensing pressure
D.carry moisture and lead to corrosion
A.frosting of the liquid line
B.higher than normal head pressure
C.a clear sight glass
D.abnormally cold reefer boxes
最新試題
Low compressor head pressure in a refrigeration system can be caused by（）.
Which of the following statements is correct concerning heat transfer?（）
If the thermal bulb of an expansion valve is incorrectly placed at the center of the coil instead of the end, it will （）.
The amount of fluid friction or internal friction inherent in a mineral lubricating oil is reflected as a measure of its （）.
Thermostatic expansion valves can be adjusted for （）.
An internal bypass is provided on some hydraulic system suction strainers to help reduce the possibility of （）.
The rate of heat transfer from a hot region to a cold region is affected most by the （）.
The control mode in which the final control element is moved from one of two flexed positions to the other is known as （）.
If the suction pressure at the refrigeration compressor is below normal, the cause can be（）.
If the relief valve on the discharge side of a hydraulic pump lifts, the cause could be （）.