Compact Heat Exchangers: Selection, Application, Design and Evaluation PDF
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Bahman Zohuri Compact Heat Exchangers Selection, Application, Design and Evaluation Compact Heat Exchangers Bahman Zohuri Compact Heat Exchangers Selection, Application, Design and Evaluation BahmanZohuri GalaxyAdvancedEngineering,Inc. Albuquerque,NM,USA ISBN978-3-319-29834-4 ISBN978-3-319-29835-1 (eBook) DOI10.1007/978-3-319-29835-1 LibraryofCongressControlNumber:2016953367 ©SpringerInternationalPublishingSwitzerland2017 Thisworkissubjecttocopyright.AllrightsarereservedbythePublisher,whetherthewholeorpartof the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilarmethodologynowknownorhereafterdeveloped. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publicationdoesnotimply,evenintheabsenceofaspecificstatement,thatsuchnamesareexempt fromtherelevantprotectivelawsandregulationsandthereforefreeforgeneraluse. Thepublisher,theauthorsandtheeditorsaresafetoassumethattheadviceandinformationinthis book are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or the editors give a warranty, express or implied, with respect to the material contained hereinorforanyerrorsoromissionsthatmayhavebeenmade. Printedonacid-freepaper ThisSpringerimprintispublishedbySpringerNature TheregisteredcompanyisSpringerInternationalPublishingAGSwitzerland This book is dedicated to my daughter Dr. Natasha Zohuri MD She always encouraged me with my publications Bahman Zohuri Preface Today’s global energy market, places many demands on power generation tech- nology including high thermal efficiency, low cost, rapid installation, reliability, environmentalcompliance,andoperationflexibility. The demand for clean, non-fossil based electricity is growing; therefore, the worldneedstodevelopnewnuclearreactorswithhigherthermalefficiencyinorder to increase electricity generation and decrease the detrimental effects on the environment. The current fleet of nuclear power plants is classified as Generation III or less. However, these models are not as energy efficient as they should be because the operating temperatures are relatively low. Currently, groups of coun- trieshaveinitiatedaninternationalcollaborationtodevelopthenextgenerationof nuclear reactors called Generation IV. The ultimate goal of developing such reactors is to increase the thermal efficiency from what currently is in the range of30–35%to45–50%.Thisincreaseinthermalefficiencywouldresultinahigher productionofelectricitycomparedtocurrentPressurizedWaterReactor(PWR)or BoilingWaterReactor(BWR)technologies. A number of technologies are being investigated for the Next Generation Nuclear Plant that will produce heated fluids at significantly higher temperatures thancurrentgenerationpowerplants.Thehighertemperaturesoffertheopportunity to significantly improve the thermodynamic efficiency of the energy conversion cycle. One of the concepts currently under study is the Molten Salt Reactor. The coolant fromtheMolten SaltReactor maybeavailable attemperaturesashighas 800–1000 (cid:1)C. At these temperatures, an open Brayton cycle combined with and Rankinebottomingcycleappearstohavesomestrongadvantages. Combined-cycle thermal efficiency increases as gas turbine specific power increases.Thegasturbinefiringtemperatureistheprimarydeterminantofspecific power. Gasturbineengines,bothaircraftandindustrialpowergeneration,representone of the most aggressive applications for structural materials. With ever growing demands for increasing performance and efficiencies, all classes of materials are beingpushedtohighertemperaturecapabilities.Thesematerialsmustalsosatisfy vii viii Preface stringentdurabilityandreliabilitycriteria.Asmaterialsaredevelopedtomeetthese demanding requirements, the processing of these materials often becomes very complicated and expensive. As a result, the cost of materials and processes has become a much larger consideration in the design and application of high perfor- mance materials. Both the aircraft engine and power generation industries are highly cost competitive, and market advantage today relies on reducing cost as wellasincreasingperformanceandefficiency. The distributed power generation market and renewing attention to renewable sourceofenergyputssomeinterestingdemandonanewaspectofheatexchangers andtheircompactnessgoingforwardwithbetterefficiencyofpowerplantwhether itisgasdriven,fossilfueloranewgenerationofnuclearplanet. For the nuclear power plant, in particular new generation and small modular reactors(SMRs),oneofthemosteconomicalsolutionstodayistogeneratepower throughsmallgasturbinesystemsintheformofBraytoncyclecombinedwiththese reactors. These gas turbines arbitrarily can be categorized as micro-turbines with outputof(5–200kW)andmini-turbineswithoutputof(200–500kW).Thethermal efficiencyofsuchmicro-turbinesisabout20%orlessifnorecuperatorisusedin the system. Using a recuperator (regenerator can also be considered but has a number of problems) operating at 87% effectiveness, the efficiency of the gas turbine system increases to about 30%, a substantial performance improvement. However, cost of the recuperator is about 25–30% of the total power plant, therefore total cost of ownership and return on investments are not very well justified. This necessitates the use of all prime surface heat exchangers with no brazing. Thus the quest for a novel design of new generation compact heat exchangers in support of such combined cycle is there and understanding of such innovativeapproachamongengineersandscientistinthefieldisrisingrapidly. In order to achieve the above described situation and usage of technology an approachsuchascombinedcycledrivenefficiencyofpowerplantseithernuclearor otherwise demands a better and more compact heat exchanger utilizing Brayton, Rankinecycleoracombinationofthemasbottomingortopingconfiguration. This book, after providing the necessary concise information on all aspects of this innovative approach such as combined cycle and associated turbines such as micro-turbinescombined,movesontothediscussiononvarioustypesofcompact heat exchanger surfaces and novel designs that can be considered for the cost effectiveheatexchangersandpackaginginthesystem. The simple Brayton cycle is modified to include recuperators or compact heat exchangers (which will transfer heat from the turbine exhaust to preheat com- pressed highpressureairbeforegoingtothecombustionchamber),itwillrequire lessfueltoobtainthedesiredturbineinlettemperatureofcompressedairandalso theoptimumpressureratio(eitherforcompressororturbine)isreducedtotypically 3–4.Thisimprovesthethermalefficiencyofthecycle.Alternatively,aregenerator canalsobeusedreplacingarecuperator. Development of high temperature/high strength materials, corrosion resistant coatings, and improved cooling technology have led to increases in gas turbine firingtemperatures.Thisincreaseinfiringtemperatureistheprimarydevelopment Preface ix thathasledtoincreasesinCombinedCycleGasTurbine(CCGT)thermalefficien- cies.Theimprovementsincombined-cyclethermalefficienciesandthecommercial development of combined-cycle power plants have proceeded in parallel with advancesingasturbinetechnologies. Compact heat-exchangers, filters, turbines, and other components in integrated Next Generation Nuclear Power Plant combined cycle systems must withstand demanding conditions of high temperatures and pressure differentials. Under the highlysulfidingconditionsofthehightemperaturesuchasinlethotsteamorother relatedenvironmentaleffects,theperformanceofcomponentsdegradesignificantly with timeunlessexpensive highalloy materials areused. Depositionofasuitable coatingonalowcostalloymayimproveitsresistancetosuchsulfidationattackand decrease capital and operating costs. A review of the literature indicates that the corrosion reaction is the competition between oxidation and sulfidation reactions. TheFe-andNi-basedhigh-temperaturealloysaresusceptibletosulfidationattack unless they are fortified with high levels of Cr, Al, and Si. To impart corrosion resistance, these elements need not be in the bulk of the alloy and need only be presentatthesurfacelayers. Those that practice the art of Nuclear or Mechanical Engineering must have a physical and intuitive understanding of the mechanisms and balances of forces, which control the transport of heat and mass in all physical systems. This under- standingstartsatthemolecularlevel,withintermolecularforcesandthemotionof molecules, and continues to the macroscopic level where gradients of velocity, temperature, and concentration drive the diffusion of momentum, heat, and mass, and the forces of pressure, inertia, and buoyancy balance to drive convection of fluids. This text covers the fundamentals of combined cycle that is required to under- standelectricalpowergenerationsystemsanddrivenefficiencyofcombinedcycle. Itthencoverstheapplicationoftheseprinciplestonuclearreactorpowersystems.It isageneralapproachtoBraytoncombinedcycletext,andaimedatexplainingthe fundamentals of combined cycle with these compact heat exchangers in the loop and applying them to the challenges facing actual nuclear power systems. It is writtenatanundergraduatelevel,butshouldalsobeusefultopracticingengineers andscientistsaswell. Chapter1providesthebasicdefinitionsandprinciplesbehindthebasicandold science of thermodynamics that one needs to understand the study of energy, energytransformations,anditsrelationtomatter,whereweneedtousetheanalysis of thermal system or thermal hydraulic through the application of the governing conservation equations, namely Conservation of Mass, Conservation of Energy (firstlawofthermodynamics),thesecondlawofthermodynamics,andtheproperty relations.Energycanbeviewedastheabilitytocausechanges.Thischapterallows us to have a better understanding of Compact Heat Exchangers (CHEs) and their designsforatypicalpowerplantlayoutandthescopeofthermodynamicsbehindit aspartofCHEsapplications. Chapter2coversthegeneralaspectofheatexchangesandwhattypesthereare as well as general rules of their designs, before we launch to specifics about
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