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


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1.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

2.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

3.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

4.单项选择题The cetane rating of diesel fuel is an indication of the ()

A.ignition quality of the fuel
B.calorific value of the fuel
C.flash point of the fuel
D.rate of fuel consumption

5.单项选择题The condensers located in various stages of a flash evaporator are cooled by()

A.distillate
B.seawater
C.brine
D.air

8.单项选择题To shut down a diesel engine after it exceeds the set maximum speed,which type of device listed should be used?()

A.Speed limiting governor
B.Over-speed governor
C.Over-speed trip
D.Over-speed relay

10.单项选择题Thermostatic steam pressure reducing valves are used in the fuel oil service system to control the()

A.double bottom fuel oil tank temperature
B.heater supply steam flow
C.pressure of the fuel supplied to the burners
D.attemperator steam flow in the heater discharge circuit