_aspen换热设计模式教程之蒸发.pdf

《_aspen换热设计模式教程之蒸发.pdf》由会员上传分享，免费在线阅读，更多相关内容在行业资料-天天文库。

1、BoilingDesignonAspenPlus(Heat-Exchangerdesignwithaphasechange)Author:JimLang(©SDSM&T,2000)ThisportioncontinueswiththedesignofheatexchangersonAspen.Wewilltakeamorein-depthlookattwoimportantprocessesinChemicalEngineering:boilingandcondensation.Thelatterwillbecoveredlater.Thefoll

2、owingexamplewillaideinteachingboilingconceptsinAspen.ProblemStatement:TheFreon-12streamusedinthepreviousexampleisnowflowingat90kmol/hrwithatemperatureof270Kandapressureof3atm.Theplantmanagerwantstovaporizethisstreamforaunitoperationlaterintheplant.Ethyleneglycolisnowavailablea

3、t340Kand2atm.Theplantmanagerrecommendsusing80BWGtubingforthisoperation,andthepressuredropshouldbeminimizedasmuchaspossible.SchematicEthyleneGlycolTi=340kFreon–12Pi=2atm90kmol/hrTi=270KFreon-12To=TsatPi=3atmVaporfraction=1.0EthyleneGlycolTo=300KVaporizerDesignProcedure©SDSM&T2/

4、13Inthissituation,thereisaphasechangeintheFreonstream.OurpurposeistodesignaheatexchangerthatwillprovideenoughenergyfortheFreontoboil.Boilingisaspecialformofheattransferandneedsspecialconsiderations.Therefore,beforestartingcalculationsonAspen,becomefamiliarwiththemechanismsofbo

5、ilingbyreadingthefollowing.Recommendedreadings:thPerry’s7edition—pgs.5-22through5-23IncroperaandDeWitt—pgs.538-546.CoulsonandRichardson—670-671andexample12.10.Geankoplis—pg.259through262GeneraldesignconsiderationsMostofthetimekettle-typereboilersareusedinboilingprocessesforhea

6、texchangerdesign.Examplesofreboilerscanbeseenonpg.11-34and11-37inreferencefive.Kettle-typereboilersaresetupinwhichthecoldprocessstreamentersnearthebottomandmakescontactwiththetubebundlewhichhousesthehotstream.Thecoldliquidformsa“pool”aroundthetubebundleinwhichtheheattransferta

7、kesplaceandtheliquidisboiledoff.Reboilershaveahugeshellareaorvaporspaceinordertoaccommodateforthehugechangeinvolumegoingfromaliquidtoagas.Thelayoutdesignismuchthesameforanormalshell-and-tubeheatexchanger;theamountofrequiredareaisfoundfirst,thenthetubebundleisdesigned,andfinall

8、ytheshellandvaporspacearecalculated.Theshelldiameterisrelated