单项选择题
A.Thermal expansion valve frozen open B.Suction gas heat exchanger bypassed C.Condenser clogged or fouled D.High pressure cutout switch inoperative
The usual symptoms of cavitation in a centrifugal pump ...
单项选择题The usual symptoms of cavitation in a centrifugal pump is （）.
A.noise and vibration B.an increase in discharge pressure C.an increase in suction pressure D.lifting of the relief valve
One cause of high head pressure occurring in a refriger...
单项选择题One cause of high head pressure occurring in a refrigeration system can be （）.
A.insufficient cooling water flow to the condenser B.a low refrigerant charge in the system C.the liquid valve is open too much D.high evaporator superheat
The control mode in which the final control element is ...
单项选择题The control mode in which the final control element is moved from one of two flexed positions to the other is known as （）.
A.dead band action B.neutral zone action C.range D.on-off action
