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单选题
An excessive charge of refrigerant in an air-cooled refrigeration system can cause （）.
A
oil foaming in the compressor
B
higher than normal suction and discharge pressures with a higher box temperature
C
higher than normal discharge pressure with a normal box temperature
D
the compressor to run continuously
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考题
Which of the conditions listed will cause a refrigeration compressor to run constantly without simultaneously decreasing the temperature in the refrigerated space?( )A.Shortage of refrigerant oilB.Slight shortage of refrigerantC.Excessive condenser cooling water flowD.Faulty expansion valve
考题
Low compressor head pressure in a refrigeration system can be caused by ___.A.insufficient condenser cooling waterB.excessive condenser cooling waterC.air in the refrigeration systemD.excessive refrigerant in the system
考题
Sweating of the refrigeration system compressor crankcase is caused by_______ .A.too much superheatB.insufficient superheatC.suction pressure too lowD.excessive refrigerant returning to the compressor
考题
Which of the following problems could cause the high pressure cutout switch to shut down the compressor in a refrigeration system?A.A shortage of liquid refrigerant.B.Excessive frost on the evaporator.C.Excessive condenser cooling water.D.Insufficient condenser cooling water flow.
考题
I don‘t think the charge for overhauling the equipment is excessive in _______ to its size. A. correspondence B. equation C. proportion D. dimension
考题
The experiment in physics is Prof Strong．__________A．in’charge ofB．taking charge ofC．in the charge ofD．taking the charge of
考题
In a chilled(冷的) water air conditioning unit using a reciprocating compressor, the refrigerating effect of the primary refrigerant can be increased by ______.A.increasing refrigerant pressure in the coilB.increasing chilled water flow through the coolerC.sub-cooling the refrigerant in the condenserD.superheating the refrigerant in the compressor
考题
Maintaining the lowest possible scavenging air temperature at all times is not recommended due to the possibility of the ______.A.air charge density becoming too highB.piston crown surfaces becoming too coldC.formation of excessive quantities of condensateD.compression pressure being greatly reduced
考题
Excessive circulation of the lubricating oil with the refrigerant in a refrigeration system will cause______.A.carbon deposits on the compressor suction valvesB.the evaporator temperature to increaseC.rapid corrosion of the thermal expansion valveD.no operating problems
考题
单选题As the refrigerant passes through the valve orifice, its pressure is reduced and part of the refrigerant turns into （）.A
liquidB
oily mixtureC
emulsionD
vapor
考题
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Maintaining the lowest possible scavenging air temperature at all times is not recommended due to the possibility of the （）.A
air charge density becoming too highB
piston crown surfaces becoming too coldC
formation of excessive quantities of condensateD
compression pressure being greatly reduced
考题
单选题Air entering an air-cooled refrigeration system is indicated by （）.A
frosting of the liquid lineB
higher than normal head pressureC
a clear sight glassD
abnormally cold reefer boxes
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 a refrigeration compressor will not start, the reason may be （）.A
the pressure regulating valve is not closingB
an excessive lack of refrigerant in the systemC
badly leaking discharge valvesD
worn piston rings
考题
单选题Before charging a refrigeration unit, the refrigerant charging lines should be（）A
flushed with clean refrigerant oilB
purged with the refrigerantC
washed with an ammonia and alcohol solutionD
grounded to compressor
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
you should close in on the suction valve
考题
单选题A liquid sight flow indicator in a refrigeration system is examined and gas bubbles are noted in motion with the fluid flowThis means （）.A
the system is fully chargedB
there is air leaking in from the condenserC
ice crystals are forming in the refrigerantD
the system contains less than a full charge of refrigerant
考题
单选题In a chilled water air conditioning unit using a reciprocating compressor, the refrigerating effect of the primary refrigerant can be increased by （）.A
increasing refrigerant pressure in the coilB
increasing chilled water flow through the coolerC
sub-cooling the refrigerant in the condenserD
superheating the refrigerant in the compressor
考题
单选题Saltwater is typically provided to a refrigeration system to （）.A
cool the expansion valveB
prevent refrigerant superheatingC
condense the refrigerant gasD
prevent motor overheating
考题
单选题One cause of high head pressure occurring in a refrigeration system can be （）.A
insufficient cooling water flow to the condenserB
a low refrigerant charge in the systemC
the liquid valve is open too muchD
high evaporator superheat
考题
单选题The thermostatic valve has a throttling action, that is to say the valve can（）A
stop the refrigerant from flowingB
force the refrigerant to flowC
cause the refrigerant pressure to riseD
cause the refrigerant pressure to fall
考题
单选题Which of the listed statements is a characteristic of the liquid charged power element used with thermostatic expansion valves?（）A
At the designed operating temperature, the liquid refrigerant charge has changed to a vaporB
The liquid refrigerant tends to collect at the bellows or diaphragm and reduces the valve sensitivityC
The sensing bulb is empty of liquid refrigerant charge at the designed operating temperatureD
The sensing bulb is never emptied of liquid refrigerant under normal operating conditions
考题
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The bus was _____ the driver.A
in charge ofB
in the charge ofC
take charge ofD
free of charge
考题
单选题A sight glass is installed in the liquid line to indicate the condition of the refrigerant charge and may also indicate the （）.A
condition of the expansion valveB
moisture in the systemC
condition of the compressor suction valvesD
condenser temperature
考题
单选题Excessive circulation of the lubricating oil with the refrigerant in a refrigeration system will cause （）.A
carbon deposits on the compressor suction valvesB
the evaporator temperature to increaseC
rapid corrosion of the thermal expansion valveD
no operating problems
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