Twoshell-and-tubeheatexchangers(STHXs)usingcontinuoushelicalbafflesinsteadofsegmentalbafflesusedinconventionalSTHXswereproposed,designed,andtestedinthisstudy.ThetwoproposedSTHXshavethesametubebundlebutdifferentshellconfigura-tions.Theflowpatternintheshellsideoftheheatexchangerwithcontinuoushelicalbaffleswasforcedtoberotationalandhelicalduetothegeometryofthecontinuoushelicalbaffles,whichresultsinasignificantincreaseinheattransfercoefficientperunitpressuredropintheheatexchanger.Properlydesignedcontinuoushelicalbafflescanreducefoulingintheshellsideandpreventtheflow-inducedvibrationaswell.TheperformanceoftheproposedSTHXswasstudiedexperimentallyinthiswork.TheheattransfercoefficientandpressuredropinthenewSTHXswerecomparedwiththoseintheSTHXwithsegmentalbaffles.Theresultsindicatethattheuseofcontinuoushelicalbafflesresultsinnearly10%increaseinheattransfercoefficientcomparedwiththatofconventionalsegmentalbafflesforthesameshell-sidepressuredrop.Basedontheex-perimentaldata,thenondimensionalcorrelationsforheattransfercoefficientandpres-suredropweredevelopedfortheproposedcontinuoushelicalbaffleheatexchangerswithdifferentshellconfigurations,whichmightbeusefulforindustrialapplicationsandfur-therstudyofcontinuoushelicalbaffleheatexchangers.ThispaperalsopresentsasimpleandfeasiblemethodtofabricatecontinuoushelicalbafflesusedforSTHXs.

Three-dimensionalturbulentflowandheattransferinaninternallyfinnedtubewithablockedcore-tubehavebeennumericallystudiedbytherealizablek−εturbulencemodelwiththewall-functionmethod.Thenumericalmethodisvalidatedbycomparingthecalculatedresultswithexperimentaldata.Therangeofratioofblockedcore-tubeoutsidediametertoouter-tubeinsidediameter(d0/Di)isfrom0.25to0.75.Thecomputationalresultsdemonstratedthatthereexistsanoptimalratioof(d0/Di)underbothidenticalmassflowrateandidenticalpressuredrop.Theoptimalratioof(d0/Di),whichisreducedwiththeincreaseofmassflowrate,isapproximately0.5to0.625atgivenmassflowrateforbothconstantwalltemperatureanduniformwallheatflux.Theoptimalratioof(d0/Di)atagivenpressuredropisfrom0.44to0.50,whichisalsoslightlyreducedwiththeincreaseofpressuredrop.Furthermore,theoptimalratioof(d0/Di)isnotsensitivetothenumberofcross-sectionwavyfinsofaninternallylongitudinalfinnedtube,intherangeofafinwavenumberof15–25.