單項(xiàng)選擇題In the presence of an open flame or hot surfaces, chlorinated fluorocarbon refrigerants decomposes and from （）

A.petroleum crystals
B.phosgene gas
C.water vapor
D.carbon monoxide


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1.單項(xiàng)選擇題In an operating refrigeration system low on refrigerant, a liquid line sight glass will（）

A.be clear
B.be blue
C.be light green
D.show bubbles

2.單項(xiàng)選擇題The thermal expansion valve reacts directly to the （）

A.temperature in the space being cooled
B.liquid refrigerant pressure at the solenoid valve
C.pressure drop across the evaporator coils
D.refrigerant gas superheat at the coil outlet

3.單項(xiàng)選擇題When transmitted by a reduction gear, diesel engine speed is reduced and the torque available for work （）

A.remains the same
B.is reduced
C.is increased
D.is eliminated

4.單項(xiàng)選擇題Pitting in the area close to the pitch line and on the same end of each gear tooth of a reduction gear unit would be caused by （）

A.corrosion on the gears
B.excessive gear speed
C.dirt in the oil
D.misalignment of the gears

5.單項(xiàng)選擇題When used with reversing reduction gears, medium-speed diesel engines should be bolted to their foundations with fitted bolts at the drive end and clearance(loosely fitted) bolts in other locations √This is done to （）

A.maintain alignment when the ship’s hull is working in heavy seas
B.ensure engine vibrations correspond to the natural frequency of the hull
C.permit the engine to expand away from the driven equipment as the engine heats up and expands
D.maintain engine thrust bearing clearances