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单选题
When a vacuum boiling evaporator works, the hot jacket water will pass over the tube stack and （） the sea water passing through the tubes.
A
dispose
B
dissolve
C
heat
D
dissipates
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A geothermal reservoir is formed when hot water is trapped under _____.A.the energy to turn a turbine
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单选题Hot gas defrosting uses the hot gas from （） to defrost the evaporator.A
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diesel enginesC
boilersD
refrigeration compressors
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单选题The fresh air intake of the inert gas system（）.A
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单选题The vacuum maintained in the salt water feed heater shell of a flash-type evaporator is generally accomplished by （）.A
a separate air ejector unitB
a direct unimpeded connection between second stage and salt water feed heaterC
either by vacuum drag or an external line from the first stage via a fixed orificeD
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考题
单选题When distilling sea water the cooling water discharging from the distiller is fed back to evaporator as feed water （）.A
to decrease scale formationB
for better cooling effectC
for more economical purposeD
to raise vacuum
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单选题Diesel engine jacket water is used in the distillation process as the （）.A
coolant for the distillateB
coolant for the brine coolerC
means of heating the feedwaterD
primary means of producing a vacuum within the distiller
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单选题The three conditions which cause engine shutdown are overspeed，low lube oil pressure，and（）.A
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High jacket water pressureC
High jacket water temperatureD
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单选题The main propulsion diesel engine jacket water temperature rises above normal, with the raw water sea suction and the expansion tank water level being normalWhich of the following problems is most likely the cause?（）A
Faulty thermostatic bypass valveB
Eroded zinc pencils in the heat exchangerC
Steam formation in the expansion tankD
Excessive leakage from jacket water pump seal
考题
单选题What is the operating principal of a flash type evaporator?（）A
Sea water is heated to boiling temperature under a vacuumB
Sea water is passed over heated plates in a thin filmC
Heated sea water is injected into a vacuum chamberD
Sea water is forced through a heated eductor
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问答题Practice 1 Heat loss by sweating depends on the fact that when a liquid evaporates, it absorbs an enormous quantity of heat from its surroundings. Therefore, when I am of sweat evaporate, a great deal of heat is absorbed from the surface of the body in contact with it. 1______ 2______ The first is the amount of movement of air surrounding the body. The second is the amount of water vapor in the air that surrounds the body. 3______ For this reason, sweat evaporates very rapidly on windy days, and the rate of heat loss by sweating is much more than on a still day. This accounts for the fact that hot still days are much less comfortable than hot windy days. In contrast, the sweat evaporates very rapidly on hot windy days, and cools the body quickly and effectively. 4______ When air is carrying the maximum amount of water vapor that it can hold, it is said to be 100% saturated with water vapor. The relative humidity of the air is said to be 100%. Under these conditions the air cannot carry any water, so no water can evaporate. When the relative humidity is high, therefore, sweat cannot evaporate. Instead, it forms large drops and runs off your skin without cooling you. 5______ It is obvious that under these conditions, evaporation will be much more rapid. Therefore, sweating will be much more effective as a method of losing heat from the body. On a hot dry day, sweat evaporates as soon as it is formed, and you feel reasonably cool even though the temperature of your environment is very high.[A] When the air is very dry and carries no water at all, the relative humidity is said to be 0%.[B] The second factor is the amount of water vapor in the air－the humidity.[C] Hot windy days are much more comfortable than hot still days.[D] This heat transfer occurs even if the environment is hotter than the body.[E] When air moves over the surface of water, the amount of evaporation is greatly increased.[F] You might expect the highest incidence of a heat stroke when the maximum temperature is 100 and humidity is 50%.[G] Two factors affect the rate of evaporation of sweat, and therefore the effectiveness of sweating as a method of cooling the body.
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单选题Less scale formation occurs in a flash evaporator than in a submerged tube evaporator because （）.A
the distillate produced has greater purityB
no boiling occurs on heat transfer surfacesC
evaporation occurs at a higher rateD
the incoming feed is at a higher temperature
考题
单选题When the water produced from most evaporator is supplied for drinking purpose, it must be treated to ensure it is biologically pure and （）.A
slightly acidicB
slightly alkalineC
no saltyD
slightly bitter
考题
单选题When distilling salt water the cooling water discharging from the distiller is fed back to evaporator as feed water （）.A
to cut down the amount of cooling water neededB
to prevent an excess amount of cooling water from being discharged to the bilgesC
to supply hot water to the evaporator for more economical operationD
None of the above is tree
考题
单选题In （）, hot diesel engine jacket water passes over the stack and heats the sea water passing through the tubes.A
a flash generatorB
a flash evaporatorC
a vacuum boiling evaporatorD
a boiler
考题
单选题With a vacuum boiling evaporator, the remainder of sea water fed to the evaporator is pumped out by （）.A
a brine pumpB
an air ejectorC
a feed pumpD
distillate pump
考题
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
考题
单选题Which of the following descriptions best identifies the operating principal of a flash-type evaporator?（）A
Sea water is heated to boiling temperature while under a vacuumB
Sea water is passed over heated plates in a thin filmC
Heated sea water is injected into a vacuum chamberD
Sea water is forced through a heated eductor
考题
单选题Which of the listed conditions will cause the feed water that has not flashed to vapor in the first-stage of a flash evaporator, to flow into the second-stage?（）A
Gravity siphon effectB
Higher vacuum in the second-stageC
Difference in brine density between first and second stagesD
lower pressure in first-stage
考题
单选题Which one of the followings might not be employed to create vacuum for flash type evaporator? （）A
high-pressure steam-driven air-ejectorB
motor-driven vacuum pumpC
water-motivated air eductorD
centrifuge pump
考题
单选题In a vacuum boiling evaporator, the fresh water generated is pumped out by （）.A
a brine pumpB
an air ejectorC
a feed water pumpD
a condensate pump
考题
单选题When steam is being raised on a boiler, the water level will normally （）.A
drop as the boiler warms upB
rise as the boiler warms upC
remain unchanged until the boiler is hot enoughD
rise and fall with the steam demand
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单选题When separating the lube oil without additive, it is usually cleaned with hot water; the aim is to remove （） from it.A
acidB
sludgeC
mechanical impurityD
salinity
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单选题Which of the listed types steam traps operates on the principle that hot water flashes to steam when its vapor pressure is rapidly reduced?（）A
Ball floatB
ThermostaticC
BimetallicD
Impulse
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