Compact Heat Exchangers: Selection, Application, Design and Evaluation

570 Pages·2017·23.78 MB·English

by  Bahman Zohuri (auth.)

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
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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