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单选题
In practice, the refrigerant flow after the evaporator is designed to ensure that the vapor leaving the evaporator is slightly ().
A
saturated
B
super-cooled
C
wet
D
superheated
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cooling coilsC
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refrigerant must be bled off the sensing line before adjustments are madeB
all refrigerant must be pumped into the receiver before adjustments are madeC
time must be allowed for conditions to stabilize in the evaporator before further adjustments are madeD
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restriction in refrigerant pipingB
air and non-condensable gases in the condenserC
water in the refrigerantD
flooding back of liquid refrigerant from the evaporator
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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
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单选题If the high-pressure switch on the compressor opens and stops the compressor a possible cause could be:()A
too much cooling water going through the condenserB
not enough refrigerant in the systemC
a leak in the evaporator coilsD
no enough cooling water going through the condenser
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单选题The heat gained per pound of refrigerant in the evaporator is known as the().A
latent heat of vaporizationB
sensible heatC
refrigerating effectD
specific heat of vaporization
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单选题Because the expansion valve is just () way open, the refrigerant is under low pressure in the evaporator.A
littleB
fewC
a littleD
a few
考题
单选题Overflow valve is used to ()A
control the fluid flow through itB
prevent the pressure before it over the specified valveC
make the pressure after it steadyD
control the direction of oil flow
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单选题The saturation temperature of the refrigerant must be () that required in the evaporator refrigerated space.A
aboveB
belowC
equal toD
None of the above
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单选题Why will a two stage flash type distilling plant tend to operate more efficiently when operating in cold seawater?()A
The colder seawater passing through the condenser tube bundles of the various stages increases evaporator vacuumB
The amount of heated feed water discharged from the feed water heater after cndenser is increasedC
Fewer non-condensable gases are created by the flow of colder seawaterD
More seawater is allowed to pass through the flint stage overflow weir
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increasing refrigerant pressure in the coilB
increasing chilled water flow through the coolerC
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superheating the refrigerant in the compressor
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refrigerant pressure in the evaporatorB
cooling water temperature to the condenserC
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solenoid valve in the liquid line
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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
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high evaporator superheat
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单选题Moisture in the refrigerant may ().A
freeze on the expansion valve seat and reduce the flow of liquid refrigerantB
emulsify the oil in the condenserC
freeze in the king valveD
clog the oil trap
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单选题Because of the reduced () in the vacuum boiling evaporator, some of the sea water boils as it flows through the tubes.A
temperatureB
water levelC
pressureD
rate of flow
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单选题The thermal expansion valve reacts directly to the ()A
temperature in the space being cooledB
liquid refrigerant pressure at the solenoid valveC
pressure drop across the evaporator coilsD
refrigerant gas superheat at the coil outlet
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单选题The refrigerant leaves the evaporator of a refrigeration system as a low pressure ().A
sub-cooled liquidB
high temperature liquidC
oil saturated liquidD
superheated vapor
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单选题After passing through the expansion valve the refrigerant should be in the state of ().A
vaporB
liquidC
solidD
None of the above is tree
考题
单选题While troubleshooting a refrigeration system for low head pressure, liquid refrigerant flooding back from the evaporator is determined to be the causeIt may be necessary to ().A
change the expansion valve adjustmentB
readjust the water regulating valve to increase the flow of waterC
purge air from the condenserD
clean the waterside of the condenser
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单选题The steam coils in a high pressure evaporator used for saltwater service should be de-scaled with ().A
a needle gunB
soap and waterC
a wire brushD
a chipping hammer
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单选题One function of the thermal expansion valve is to()A
act as a pilot from the solenoid valveB
regulate the amount of refrigerant flow to the coilC
regulate the water flowD
turn the compressor off and on
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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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