新版轮机英语unit22_marine_disalination_plants(1)

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1、22MarinedesalinationplantsAconsiderableamountoffreshwaterisconsumedinaship.Thecrewusesonaverageabout70liter/person/dayandinapassengership,consumptioncanbeashighas225/Liter/person/day.Waterusedinthemachineryspacesasmakeupforcoolingsystemlossesmaybefreshordistilled(蒸馏水）butdistilledwat

2、erisessentialforsteamplantwherethereisawatertubeboiler.Steamshipconsumptionforthepropulsionplant(推进装置）andhotelservicescanbeashighas50tons/day.Itisnowcommonpracticetotakeononlyaminimalsupplyofportablewaterinportandtomakeuptherestbydistillationofseawater.maximalThesavedstoragecapacity

3、forwater,isavailableforcargoandincreasestheearning（盈利）poweroftheship.Avesselwhichcarriessufficientportablewaterfornormalrequirementsisrequired,ifocean-going（远洋航行的）,tocarrydistillationplantforemergencyuse.Thestate（状况，国家）oftheartofdistillingplantdesignhasevolved（发展）considerably.Avarie

4、tyofdistillingplantdesignshasbeendevelopedfromwhichthemostappropriatesystemforagivenmarinepowerplantcanbeselected.Thedistillationplantdesignsmostcommonlyconsideredformarineusecanbebroadlyclassifiedasthoseusing:Flashevaporators（闪发式蒸发器）Spray-film（喷膜式）evaporatorsSubmerged-tube（潜管式）evap

5、oratorsPlate-typeevaporators（平板式）Vapor-compressioncycles（蒸汽压缩式循环）Membraneprocesses（膜式）它的特点是海水加热器与蒸发器彼此分开，经加热器加热的海水喷到高度真空的闪发室中作雾状蒸发，因此有利于淡水质量的提高和防止蒸发器内部结垢。与前一种比较，由于闪发室内没有传热表面，故这种装置又称为无传热表面式制淡装置。FlashevaporatorsThemultistage（多级）flashevaporatorswasarevolutionary（革命性的）designdevelopment,

6、becauseunlikesubmerge-tubeevaporators,Whichhaveheatingsurfacessubmergedinboilingseawater,theflash-evaporatorconceptcausesseawaterto“flash”intowatervapor;Noboilingoccursintheheat-transfersurfaces（受热面）.Flashevaporatorsbecomewidelyacceptedforapplicationinmarinedistillingplantsprimarily

7、（主要的）becauseoftheirlowoperatingtemperatureaswellastheycanoperatethreemonthsormorewithoutfeed（给水）treatmentandwithoutshutdownforcleaning.Inadditiontobeingsmallerandlighterforagivencapacity,theflash-typeevaporatorisalsosimplertooperate,whichisanadvantagefromanautomaticstandpoint.Aflesh

8、-typeevaporatorprod