單項選擇題The purpose of the purge valve at the top of the condenser in a refrigerating system is to（）

A.remove any air that may accumulate in the system
B.take out unpleasant fumes from the refrigerant
C.vent off excess refrigerant in an emergency
D.permit opening the refrigerating system for cleaning and inspecting


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1.單項選擇題What is the purpose of sub cooling R-12 in the condenser?（）

A.to increase the system efficiency by sensible heat transfer
B.to stop the liquid from flashing
C.to reduce the load on the compressor
D.to remove latent heat of vaporization and the suction piping transfer

2.單項選擇題In terms of pressure and temperature in the refrigerant in the compressor, what happens to the primary?（）

A.its pressure and temperature are both lowered
B.its pressure and temperature are both raised
C.its pressure is lowered and its temperature is raised
D.its pressure is raised and its temperature is lowered

3.單項選擇題The solenoid valve can be typed as a（）

A.thermal valve
B.magnetic stop valve
C.bellows valve
D.bimetallic valve

4.單項選擇題If the compressor runs continually, the cause might be the（）

A.high-pressure cutout switch is jammed open
B.low-pressure switch is jammed shut
C.thermal bulb is not operating properly
D.scale trap is clogged

5.單項選擇題The bulb for the thermal expansion valve is located（）

A.in the middle of evaporator coils
B.near the evaporator coil outlet
C.near the evaporator coil inlet
D.on the bottom row of evaporator coils