单选题On a multistage flash-type evaporator, the flash chamber is （）Acombined as part of the salt water feed heaterBthe open area above the brine levels in the first and second stagesCcombined as part of the distillate coolerDanother term used to describe the vapor feed heater
单选题
On a multistage flash-type evaporator, the flash chamber is （）
A
combined as part of the salt water feed heater
B
the open area above the brine levels in the first and second stages
C
combined as part of the distillate cooler
D
another term used to describe the vapor feed heater
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The condensers located in various stages of a flash evaporator are cooled by( ).A.distillateB.seawaterC.brineD.air
The process during which liquid containing a reasonable amount of sensible heat at a particular pressure immediately changes into steam after admitted to a chamber at a lower pressure is called _____.A.boiling offB.flash evaporationC.condensationD.none of the above
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
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 （）.Acompletely filled with saltwaterBfilled with de-scaling compoundCtightly closed to exclude airDvented to the atmosphere
单选题The flash-evaporator is different with the submerged-tube evaporator in that for the former（）AWater is heated into vapor on heating surfacesBWater is vaporized by pressure differenceCThere are no heating-transfer surfacesDThere are more heating-transfer surfaces
单选题The vacuum maintained in the salt water feed heater shell of a flash-type evaporator is generally accomplished by （）.Aa separate air ejector unitBa direct unimpeded connection between second stage and salt water feed heaterCeither by vacuum drag or an external line from the first stage via a fixed orificeDthe fixed orifice provided in the steam supply line
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（）Alower condensingBhigher coolingClower coolingDhigher condensing
单选题The heated feed-water entering any flash chamber of a flash-type evaporator will（）Avaporize, with the un-flashed water remaining at the temperature at which it entered the flash chamberBvaporize, with the un-flashed eater equalizing to the saturation conditions existing in the f lash chamberCvaporize, with the remaining water a t a temperature greater than it entered the flash chamberDboil, allowing steam bubbles to rise through the brine at the bottom of the flash chamber
单选题In a flash type evaporator, all saltwater headers are vented through individual vent cocks to the（）.Asaltwater heater shellBsecond-stage condenserCatmosphereDsecond-stage flash chamber
单选题For a flash type evaporator, the seawater heater will have to maintain a enough temperature to minimize scale formation（）AlowerBhigherClowDhigh
单选题Small droplets of water entrained in the flashed vapor produced in a flash-type evaporator, are removed by the （）Aspray pipesBdemistersCcondensersDsplash baffles
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 （）.Afirst stage flash chamberBsecond stage flash chamberCfirst stage after condenserDsecond stage distilling condenser
单选题The demisters installed in a flash-type evaporator serve to （）Adeaerate the first effect distillateBfilter the condensed flash vaporsCdeaerate the first and second effect distillateDremove small water droplets entrained in the flashed vapor
单选题The efficiency of a flash type evaporator can be increased by（）Alowering brine discharge densityBdecreasing the absolute pressure of each stageCincreasing the saltwater feed heater temperatureDincreasing the pressure at the spray pipe
单选题One distinct advantage of flash type evaporators, as compared to most other evaporators, is that in a flash evaporator （）.Ahigh temperature distillate can be re- circulated to induce additional flashingBscale formation is not a severe problemCcold shocking is more effective in removing scaleDwater purity is greatly increased at high capacity
单选题Less scale formation occurs in a flash evaporator than in a submerged tube evaporator because （）.Athe distillate produced has greater purityBno boiling occurs on heat transfer surfacesCevaporation occurs at a higher rateDthe incoming feed is at a higher temperature
单选题The heated feedwater entering any flash chamber of a flash-type evaporator will（）Avaporize, with the unflashed water remaining at the temperature at which it entered the flash chamberBvaporize, with the unflashed water equalizing to the saturation conditions existing in the flash chamberCvaporize, with the remaining water at the temperature greater than it entered the flash chamberDboil, allowing steam bubbles to rise through the brine at the bottom of the flash chamber
单选题For a flash type evaporator, a demister is located the condenser（）AAfterBbeforeCinsideDoutside
单选题The advantages of flash type evaporators, as compared to submerged tube type evaporators, include （）.Aless internal corrosion because of lower brine densityBhigher temperature evaporation for lower salinity of the distillate producedCless scale formation in a flash evaporatorDless feed-water required for a flash evaporator
单选题On a multistage flash-type evaporator, the flash chamber is （）Acombined as part of the salt water feed heaterBthe open area above the brine levels in the first and second stagesCcombined as part of the distillate coolerDanother term used to describe the vapor feed heater
单选题The condensers located in various stages of a flash evaporator are cooled by（）AdistillateBseawaterCbrineDair
单选题Which of the following descriptions best identifies the operating principal of a flash-type evaporator?（）ASea water is heated to boiling temperature while under a vacuumBSea water is passed over heated plates in a thin filmCHeated sea water is injected into a vacuum chamberDSea water is forced through a heated eductor
单选题Early models of the flash-type evaporators used a separate shell-and-tube heat exchanger as the air ejector condenser.More recent models use a combined air ejector condenser with the（）Adistilling condenserBsalt water feed heaterCdistillate coolerDflash chamber
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.AlowerBhigherCthe lowerDthe higher
单选题Which one of the followings might not be employed to create vacuum for flash type evaporator? （）Ahigh-pressure steam-driven air-ejectorBmotor-driven vacuum pumpCwater-motivated air eductorDcentrifuge pump
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?（）AFeed-water heater internal tube surfacesBInternal distillate cooler tubesCFlash chamber vertical surfacesDDistilling condenser tubes
单选题Under normal operating conditions, the highest temperature and pressure conditions existing in a flash-type evaporator will occur in the （）.Afirst stageBsecond stageCdistillate coolerDsalt water feed heater
单选题In a flash distilling unit, evaporator feed (seawater) first absorbs heat in the （）.Avapor feed heaterBair ejector condenserCsaltwater heaterDdistillate cooler