单项选择题
A.Centrifugal B.Reciprocating C.Gear D.Rotary
Heavy wear in a particular area of the inner circumfere...
单项选择题Heavy wear in a particular area of the inner circumference of a packing ring may be caused by （）.
A.a high suction head B.rotating rings C.badly worn bearings D.a loose stuffing box gland
A pressure drop through the refrigerant liquid line may...
单项选择题A pressure drop through the refrigerant liquid line may cause （）.
A.solenoid valve to seize B.compressor to hunt C.formation of flash gas in the liquid line D.expansion valve to freeze open
Low compressor head pressure in a refrigeration system ...
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
