单项选择题
A purge recovery system is used in a centrifugal air conditioning or refrigeration system to （）
A.purge lube oil from the liquid refrigerant B.recover water purged from the system C.separate foul gases from the receiver D.purge non-condensable gases without losing refrigerant
单项选择题 Refrigerant entering the compressor of a refrigeration system should be in which of the following conditions?（）
单项选择题 Flame failure in an automatically fired auxiliary boiler can from a/an （）
单项选择题 Cold weather starting of a diesel engine may be made easier by（）
