单项选择题
Low compressor head pressure in a refrigeration system can be caused by（）.
A.insufficient condenser cooling water
B.excessive condenser cooling water
C.air in the refrigeration system
D.excessive refrigerant in the system
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相关考题
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单项选择题
Which of the problems listed would came the discharge temperature of an R-12 refrigeration compressor to increase?（）
A.Thermal expansion valve frozen open
B.Suction gas heat exchanger bypassed
C.Condenser clogged or fouled
D.High pressure cutout switch inoperative -
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 -
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
