A.the temperature and flow quantity of the exhaust gas ……

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?（）

A.Sub-cooled liquid
B.Sub-cooled vapor
C.Superheated vapor
D.Liquid

单项选择题Flame failure in an automatically fired auxiliary boiler can from a an （）

A.incorrect electrode setting
B.incorrect nozzle position
C.clogged fuel nozzle
D.broken high tension lead

单项选择题Cold weather starting of a diesel engine may be made easier by（）

A.decreasing the compression ratio
B.using a special fuel having a high ignition temperature
C.increasing the starting air supply
D.heating the jacket water

单项选择题Diesel engine air start system check valves are opened by （）

A.an air start cam
B.cylinder compression pressure
C.starting air pressure
D.valve springs