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单选题
Before charging a refrigeration unit, the refrigerant charging lines should be（）
A
flushed with clean refrigerant oil
B
purged with the refrigerant
C
washed with an ammonia and alcohol solution
D
grounded to compressor
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liquid receiverB
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maintain adequate coil back pressureB
prohibit flashing in the liquid lineC
reduce refrigerant volume in the systemD
reduce compressor discharge line loading
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单选题If a liquid sight flow indicator in a refrigeration system shows gas bubbles in motion passing inside of the glass, there is （）.A
too much refrigerant in the systemB
oil entrained in the refrigerantC
less than a full charge of refrigerant in the systemD
ice crystals forming in the refrigerant
考题
单选题The only means of removing the latent heat of condensation from a refrigerant in the normal refrigeration cycle is by （）.A
passing it through the expansion valveB
condensing refrigerant in the system condenserC
passing the gaseous refrigerant through the heat interchanger on the suction side of the compressorD
maintaining a high pressure on the systems receiver
考题
单选题If the head pressure of a reciprocating refrigeration compressor is excessive, （）.A
the relief valve should open before the high pressure cutoutB
the relief valve should open and allow the excess refrigerant to flow to the receiverC
the high pressure cutout switch should operate before the relief valve opensD
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单选题Foaming of the oil in a refrigeration compressor crankcase is caused by （）.A
refrigerant boiling out of solution from the lube oilB
liquid refrigerant flooding the compressor and systemC
lube oil viscosity being reduced by refrigerant dilutionD
compressor suction pressure suddenly increasing
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单选题Refrigerant is circulated through a refrigeration system by the （）.A
compressorB
condenserC
expansion valveD
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high temperature liquidC
oil saturated liquidD
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liquidB
dry saturated gasC
wet saturated gasD
superheated vapor
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单选题When a refrigeration compressor has developed a high head pressure as a result of a refrigerant overcharge, you should （）.A
increase the amount of cooling water to the condenserB
decrease the amount of cooling water to the condenserC
add more refrigerant to the systemD
remove some refrigerant from the system
考题
单选题Which of the listed refrigeration system components keeps the refrigerant circulating through the system?（）A
Expansion valveB
CondenserC
EvaporatorD
Compressor
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