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单选题
In a flash type evaporator, the brine overboard pump is vented directly to the（）
A
saltwater heater shell
B
the condensation of the saltwater feed
C
air ejectors, eductors, or a separate vacuum pump
D
condensation of the distillate
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考题
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
考题
Which of the listed problems could produce a high absolute pressure within a flash type evaporator?A.production of high salinity distillateB.seawater feed temperature below 165℃C.a leak in the first stage demisterD.a cracked distillate pump vent line
考题
All of the following steps are taken in starting a centrifugal pump，EXCEPT to ______．A.Set the relief valveB.Check the lubrication systemC.Vent the pump casingD.Open the pump suction and discharge valves
考题
单选题When a flash-type evaporator is to be secured for an extended period of time, the entire unit should be drained, cleaned, and （）.A
completely filled with saltwaterB
filled with de-scaling compoundC
tightly closed to exclude airD
vented to the atmosphere
考题
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
考题
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
higher coolingC
lower coolingD
higher condensing
考题
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
考题
单选题In a flash type evaporator, all saltwater headers are vented through individual vent cocks to the（）.A
saltwater heater shellB
second-stage condenserC
atmosphereD
second-stage flash chamber
考题
单选题Which of the listed problems could produce a high absolute pressure within a flash type evaporator?（）A
Production of high salinity distillateB
Seawater feed temperature below 165℃C
A leak in the first stage demisterD
A cracked distillate pump vent line
考题
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
考题
单选题Small droplets of water entrained in the flashed vapor produced in a flash-type evaporator, are removed by the （）A
spray pipesB
demistersC
condensersD
splash baffles
考题
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
first stage after condenserD
second stage distilling condenser
考题
单选题The demisters installed in a flash-type evaporator serve to （）A
deaerate the first effect distillateB
filter the condensed flash vaporsC
deaerate the first and second effect distillateD
remove small water droplets entrained in the flashed vapor
考题
单选题The efficiency of a flash type evaporator can be increased by（）A
lowering brine discharge densityB
decreasing the absolute pressure of each stageC
increasing the saltwater feed heater temperatureD
increasing the pressure at the spray pipe
考题
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Which of the following statements is true concerning any evaporator?（）A
High conductivity of the distillate indicates distillate salinity is excessiveB
Increasing the absolute pressure of the shell will increase the distillers capacityC
Mesh separators are used in evaporators to filter the distillateD
Reducing the brine density will reduce the heat lost overboard
考题
单选题The design of for a flash type evaporator is of critical importance because it must provide an optimum feedwater spray pattern that facilitates the flashing process, and it must also maintain a pressure differential between successive stages（）A
condenserB
flashing deviceC
lashing deviceD
vacuum pump
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
考题
单选题For a flash type evaporator, a demister is located the condenser（）A
AfterB
beforeC
insideD
outside
考题
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On a multistage flash-type evaporator, the flash chamber is （）A
combined as part of the salt water feed heaterB
the open area above the brine levels in the first and second stagesC
combined as part of the distillate coolerD
another term used to describe the vapor feed heater
考题
单选题Scale accumulation on evaporator heat exchange surfaces （）.A
increases brine densityB
increases distillate salinityC
reduces metal corrosionD
reduces heat transfer
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Under normal operating conditions, the highest temperature and pressure conditions existing in a flash-type evaporator will occur in the （）.A
first stageB
second stageC
distillate coolerD
salt water feed heater
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