Handbook for Heat Exchangers and Tube Banks design

The recently published book by the author Engineering Heat Transfer already dealt with exact computation of heat exchangers and tube banks. In design c- putationthisisaccomplishedviacorrectivefactors;thelattermakesitpossibleto compute the actual mean temperature difference by starting from the logarithmic onerelativeto?uidsinparallel?oworcounter?ow. As far as veri?cation computation is concerned corrective factors were int- ducedtocomputeacertaincharacteristicfactorcorrectlyasisfundamentalforthis typeofcomputation. Basedontheabovetheauthordecidedtoinvestigatefurtherre?neandwiden thistopic:theoutcomeofthisworkhasresultedinthishandbook. Newtypesofexchangerswereexamined;thecalculationwasre?nedtoproduce practicallyexactvaluesforthefactors. Thescopeoftheinvestigationwasincreased by widening the range of the starting factors. Furthermore a greater number of valuestobeincludedinthetableswasconsidered. Finallyafewcharacteristicsof certainvaluesofthecorrectivefactorswerehighlighted. The?rstsectionisanintroduction;itsummarizesthefundamentalcriteriaofheat transferandproceedstoillustratethebehaviorof?uidsinbothparallelandcounter ?ow. Italsoshowshowtocomputethemeanisobaricspeci?cheatforsome?uids; itillustratesthesigni?canceofdesigncomputationandveri?cationcomputation. In additionitillustrateshowtoproceedwithheatexchangersandtubebankstocarry outbothdesignandveri?cationcomputationcorrectly. AppendixAthenincludes36tablesasareferencefordesigncomputationThe tablescontainthecorrectivefactorsrequiredtoobtaintheactualmeantemperature differencebystartingfromthemeanlogarithmictemperaturedifferencerelativeto ?uidsinparallel?oworcounter?ow. Finally Appendix B includes 35 tables for veri?cation computation. As far as heatexchangers areconcerned itshowsthevaluesoffactor ? whichisrequired forthistypeofcomputation. Thevaluesofthecorrectivefactorsforcoilsandtube banksarealsopresented. MilanoItaly DonatelloAnnaratone v Notation c=speci?cheat(J/kgK) d=diameter(m) E=ef?ciencyfactor h=enthalpy(kJ/kg) k=thermalconductivity(W/mK) M=mass?owrate(kg/s) m=massmoisturepercentage(%) q=heatpertimeunit(W) 2 S=surface(m ) ? t=temperature( C) 2 U=overallheattransfercoef?cient(W/m K) x=thickness(m) 2 ? =heattransfercoef?cient(W/m K) ? =characteristicfactor ? =characteristicfactor ? =ef?ciency ? =correctivefactor ? =correctivefactor ? =characteristicfactor ? ?t=temperaturedifference( C) vii viii Notation Superscripts =heating?uid =heated?uid Subscripts c=counter?ow e=exchanger i=inside l=logarithmic m=mean o=outside p=constantpressure(isobaric)parallel?ow w=wall 1=inlet(forheatingorheated?uid) 2=outlet(forheatingorheated?uid) Contents 1 Introduction to Computation . . . . . . . . . . . . . . . . . . . . . 1 1. 1 GeneralConsiderations . . . . . . . . . . . . . . . . . . . . . . 1 1. 2 MeanIsobaricSpeci?cHeat . . . . . . . . . . . . . . . . . . . . 3 1. 2. 1 WaterandSuperheatedSteam . . . . . . . . . . . . . . . 4 1. 2. 2 AirandOtherGases. . . . . . . . . . . . . . . . . . . . 4 2 Design Computation. . . . . . . . . . . . . . . . . . . . . . . . . . 7 2. 1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 2. 2 FluidsinParallelFloworinCounterFlow . . . . . . . . . . . . 8 2. 3 TheMeanDifferenceinTemperatureinReality . . . . . . . . . 12 2. 3. 1 FluidsinCrossFlow. . . . . . . . . . . . . . . . . . . . 14 2. 3. 2 HeatExchangers. . . . . . . . . . . . . . . . . . . . . . 15 2. 3. 3 Coils. . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 2. 3. 4 TubeBankswithVariousPassagesoftheExternalFluid . 21