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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 purity
B
no boiling occurs on heat transfer surfaces
C
evaporation occurs at a higher rate
D
the incoming feed is at a higher temperature
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The condensers located in various stages of a flash evaporator are cooled by( ).A.distillateB.seawaterC.brineD.air
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In a flash type evaporator, all saltwater heaters are vented through individual vent cocks to the ______.A.saltwater heater shellB.second-stage condenserC.atmosphereD.second-stage flash chamber
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单选题Excessive scale formation in a distilling plant may result from （）.A
poor distillate qualityB
reduced evaporator capacityC
low brine concentrationD
improper vacuum regulation
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单选题The flash-evaporator is different with the submerged-tube evaporator in that for the former（）A
Water is heated into vapor on heating surfacesB
Water is vaporized by pressure differenceC
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There are more heating-transfer surfaces
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单选题A flash-type evaporator discharges heated seawater into a chamber that is maintained at a pressure than the vapor pressure of the entering heated seawater, and subsequently the flashed water vapor thereby produced（）A
lower condensingB
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单选题The heated feed-water entering any flash chamber of a flash-type evaporator will（）A
vaporize, with the un-flashed water remaining at the temperature at which it entered the flash chamberB
vaporize, with the un-flashed eater equalizing to the saturation conditions existing in the f lash chamberC
vaporize, with the remaining water a t a temperature greater than it entered the flash chamberD
boil, allowing steam bubbles to rise through the brine at the bottom of the flash chamber
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单选题In a flash type evaporator, all saltwater headers are vented through individual vent cocks to the（）.A
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单选题The scale trap is located between the （）A
king valve and the expansion valveB
solenoid valve and expansion valveC
evaporator and receiverD
compressor and evaporator
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单选题For a flash type evaporator, the seawater heater will have to maintain a enough temperature to minimize scale formation（）A
lowerB
higherC
lowD
high
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单选题In the operation of a flash type evaporator equipped with air ejectors,the air and non- condensable gases are evacuated directly from the （）.A
first stage flash chamberB
second stage flash chamberC
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second stage distilling condenser
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单选题Operating a propulsion diesel engine at less than 30% of designed normal load for prolonged periods will result in （）.A
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单选题The demisters installed in a flash-type evaporator serve to （）A
deaerate the first effect distillateB
filter the condensed flash vaporsC
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单选题One distinct advantage of flash type evaporators, as compared to most other evaporators, is that in a flash evaporator （）.A
high temperature distillate can be re- circulated to induce additional flashingB
scale formation is not a severe problemC
cold shocking is more effective in removing scaleD
water purity is greatly increased at high capacity
考题
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
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考题
单选题The heated feedwater entering any flash chamber of a flash-type evaporator will（）A
vaporize, with the unflashed water remaining at the temperature at which it entered the flash chamberB
vaporize, with the unflashed water equalizing to the saturation conditions existing in the flash chamberC
vaporize, with the remaining water at the temperature greater than it entered the flash chamberD
boil, allowing steam bubbles to rise through the brine at the bottom of the flash chamber
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单选题For a flash type evaporator, a demister is located the condenser（）A
AfterB
beforeC
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单选题The advantages of flash type evaporators, as compared to submerged tube type evaporators, include （）.A
less internal corrosion because of lower brine densityB
higher temperature evaporation for lower salinity of the distillate producedC
less scale formation in a flash evaporatorD
less feed-water required for a flash evaporator
考题
单选题The condensers located in various stages of a flash evaporator are cooled by（）A
distillateB
seawaterC
brineD
air
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单选题Scale accumulation on evaporator heat exchange surfaces （）.A
increases brine densityB
increases distillate salinityC
reduces metal corrosionD
reduces heat transfer
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单选题That the scale of any part of a chart to be larger than the scale of the survey is（）.A
very rareB
commonC
oftenD
reasonable
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单选题In a flash evaporator, scale as a result of higher than normal temperatures in most likely to occur in the （）A
second stage feed heaterB
saltwater feed heaterC
distillate coolerD
second stage vapor separator
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单选题More than one stage of evaporation can take place by admitting the sea water into chambers with progressively （） pressure in the flash evaporator.A
lowerB
higherC
the lowerD
the higher
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单选题On which of the following heated surfaces of a flash type evaporator would you be more likely to find soft scale formation?（）A
Feed-water heater internal tube surfacesB
Internal distillate cooler tubesC
Flash chamber vertical surfacesD
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单选题An increase in the heat load to a refrigeration system will cause （）.A
the suction pressure to decreaseB
the suction temperature to increaseC
increased ice formation on the evaporator coilD
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单选题The primary reason low pressure evaporators produce distillate more efficiently, and with less scale formation, than high pressure evaporators is （）.A
evaporation is accomplished in a vacuumB
due to the higher temperature of the incoming feedC
due to the latent heat of evaporation principleD
evaporation in a submerged medium produces more distillate
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