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- ducedtocomputeacertaincharacteristicfactorcorrectly,asisfundamentalforthis typeofcomputation. Basedontheabove,theauthordecidedtoinvestigatefurther,re?ne,andwiden thistopic:theoutcomeofthisworkhasresultedinthishandbook. Newtypesofexchangerswereexamined;thecalculationwasre?nedtoproduce practicallyexactvaluesforthefactors. Thescopeoftheinvestigationwasincreased by widening the range of the starting factors. Furthermore, a greater number of valuestobeincludedinthetableswasconsidered. Finally,afewcharacteristicsof certainvaluesofthecorrectivefactorswerehighlighted. The?rstsectionisanintroduction;itsummarizesthefundamentalcriteriaofheat transferandproceedstoillustratethebehaviorof?uidsinbothparallelandcounter ?ow. Italsoshowshowtocomputethemeanisobaricspeci?cheatforsome?uids; itillustratesthesigni?canceofdesigncomputationandveri?cationcomputation. In addition,itillustrateshowtoproceedwithheatexchangersandtubebankstocarry outbothdesignandveri?cationcomputationcorrectly. AppendixAthenincludes36tablesasareferencefordesigncomputation,The 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. Milano,Italy 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 3 Veri?cation Computation . . . . . . . . . . . . . . . . . . . . . . . 25 3. 1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 3. 2 FluidsinParallelFloworinCounterFlow . . . . . . . . . . . . 25 3. 3 Factor?inRealCases. . . . . . . . . . . . . . . . . . . . . . . 33 3. 3. 1 FluidswithCrossFlow . . . . . . . . . . . . . . . . . .