Application of Compact Heat Exchangers For Combined Cycle Driven Efficiency In Next Generation Nuclear Power Plants: A Novel Approach

385 Pages·2015·12.96 MB·English

by  Bahman Zohuri

Bahman Zohuri
Application of Compact
Heat Exchangers For
Combined Cycle Driven
Effi ciency In Next
Generation Nuclear
Power Plants
A Novel Approach
Application of Compact Heat Exchangers
for Combined Cycle Driven Efficiency
in Next Generation Nuclear Power Plants

Bahman Zohuri
Application of Compact Heat
Exchangers for Combined
Cycle Driven Efficiency
in Next Generation Nuclear
Power Plants
A Novel Approach
BahmanZohuri
GalaxyAdvancedEngineering,Inc.
Albuquerque,NM,USA
ISBN978-3-319-23536-3 ISBN978-3-319-23537-0 (eBook)
DOI10.1007/978-3-319-23537-0
LibraryofCongressControlNumber:2015949382
SpringerChamHeidelbergNewYorkDordrechtLondon
©SpringerInternationalPublishingSwitzerland2016
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This book is dedicated to my daughter,
Natalie.
She has always encouraged me with
my publications.
Bahman Zohuri

Preface
Today’sglobalenergymarketplacesmanydemandsonpowergenerationtechnol-
ogy, including high thermal efficiency, low cost, rapid installation, reliability,
environmentalcompliance,andoperationalflexibility.
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, a group of
countrieshasinitiatedaninternationalcollaborationtodevelopthenextgeneration
of nuclear reactors, called Generation IV. The ultimate goal of developing such
reactorsistoincreasethethermalefficiencyfromthecurrentrangeof30–35%to
45–50%.Thisincreaseinthermalefficiencywouldresultinahigherproductionof
electricitycomparedtocurrentPressurizedWaterReactor(PWR)orBoilingWater
Reactor(BWR)technologies.
A number of technologies are being investigated for the Next Generation
Nuclear Plant (NGNP) that will produce heated fluids at significantly higher
temperatures than current generation power plants. The higher temperatures offer
the opportunity to significantly improve the thermodynamic efficiency of the
energy conversion cycle. One ofthe concepts currently under study is the Molten
Salt Reactor. The coolant from the Molten Salt Reactor may be available at
temperaturesashighas800–1000(cid:1)C.
At these temperatures, an open Brayton cycle combined with a Rankine
bottomingcycleappearstohavesomestrongadvantagesoveranyothercombina-
tionsofothercycles.
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
vii
viii Preface
demands for increasing performance and efficiencies, all classes of materials are
beingpushedtohighertemperaturecapabilities.Thesematerialsmustalsosatisfy
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.
Given the rise of the distributed power generation market, and the renewed
attentiontonuclearpowerplants(inparticularnewgenerationandsmallmodular
reactors),oneofthemosteconomicalsolutionstodayistogeneratepowerthrough
smallgasturbinesystemsintheformofBraytoncycles,combinedwiththesenew
and small modular reactors (SMRs). These gas turbines arbitrarily can be catego-
rizedasmicro-turbineswithoutputof(5–200kW)andmini-turbineswithoutputof
(200–500kW).Thethermalefficiencyofsuchmicro-turbinesisabout20%orless
ifnorecuperatorisusedinthesystem.Usingarecuperator(aregeneratorcanalso
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 perfor-
manceimprovement.However,thecostoftherecuperatorisabout25–30%ofthe
total power plant; therefore total cost of ownership and return on investments are
notverywelljustified.Thisnecessitatestheuseofallprimesurfaceheatexchangers
with no brazing. Thus the quest for novel designs to enable a new generation of
compact heat exchangers in support of combined cycles is underway, and an
understanding of such innovative approaches among engineers and scientists is
risingrapidly.
Inthisbook,afterprovidingthenecessaryconciseinformationonallaspectsof
this innovative approach such as combined cycle and associated turbines such as
micro-turbinescombined,thengoestothediscussiononvarioustypesofcompact
heat exchanger surfaces and novel designs that can be considered for the
costeffectiveheatexchangersandpackaginginthesystem.
The simple Brayton cycle is modified to include a recuperator (which will
transfer heat from the turbine exhaust to preheat compressed high pressure air
before going to the combustion chamber); it will require less fuel to obtain the
desiredturbineinlettemperatureofcompressedairandalsotheoptimumpressure
ratio (either for compressor orturbine) is reduced totypically3–4. Thisimproves
the thermal efficiency of the cycle. Alternatively, a regenerator can also be used
replacingarecuperator.
The development of high temperature/high strength materials, corrosion-
resistant coatings, and improved cooling technology has led to increases in gas
turbine firing temperatures. This increase in firing temperature is the primary
development that has led to increases in Combined Cycle Gas Turbine (CCGT)
thermalefficiencies.Theimprovementsincombined-cyclethermalefficienciesand
the commercial development of combined-cycle power plants have proceeded in
parallelwithadvancesingasturbinetechnologies.
Preface ix
The Generation IV International Forum (GIF) Program has narrowed design
optionsofthenuclearreactorstosixconcepts.TheseconceptsareGas-cooledFast
Reactor (GFR), Very High Temperature Reactor (VHTR), Sodium-cooled Fast
Reactor(SFR),Lead-cooledFastReactor(LFR),MoltenSaltReactor(MSR),and
SupercriticalWater-cooledReactor(SCWR).Thesenuclear-reactorconceptsdiffer
in their design in aspects such as the neutron spectrum, coolant, moderator, and
operatingtemperatureandpressure.
Therearemanydifferenttypesofpowerreactors.Whatiscommontothemallis
thattheyproducethermalenergythatcanbeusedforitsownsakeorconvertedinto
mechanical energy and ultimately, in the vast majority of cases, into electrical
energy. Thermal-hydraulic issues related to both operating and advanced reactors
are presented. Further thermal-hydraulics research and development is continuing
inbothexperimentalandcomputationalareasforoperatingreactors,reactorsunder
construction or ready for near-term deployment, and advanced Generation-IV
reactors.Asthecomputingpowerincreases,thefine-scalemulti-physicscomputa-
tional models, coupled with the systems analysis code, are expected to provide
answers to many challenging problems in both operating and advanced reactor
designs.
Compact heat-exchangers, filters, turbines, and other components in integrated
Next-Generation Nuclear Power Plant combined cycle system must withstand
demanding conditions of high temperatures and pressure differentials. Under the
highlysulfidingconditionsofthehightemperaturesuchasinlethotsteamorother
relatedenvironmentaleffects,theperformanceofcomponentsdegradesignificantly
with timeunlessexpensive highalloy materials areused. Depositionofasuitable
coatingonalow-costalloymayimproveitsresistancetosuchsulfidationattackand
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 Engineering must have a physical and
intuitiveunderstandingofthemechanismsandbalancesofforces,whichcontrolthe
transportofheatandmassinallphysicalsystems.Thisunderstandingstartsatthe
molecular level, with intermolecular forces and the motion of molecules, and
continues to the macroscopic level where gradients of velocity, temperature, and
concentration drive the diffusion ofmomentum, heat, and mass, and the forcesof
pressure,inertia,andbuoyancybalancetodriveconvectionoffluids.
This text covers the fundamentals of combined cycles required to understand
electricalpowergenerationsystemsandrelatedefficiencyissues.Itthencoversthe
application of these principles to nuclear reactor power systems. It is a general
approachtoaBraytoncombinedcycletext,aimedatexplainingcombinedcyclesas
deployed with compact heat exchangers in the loop, and applying them to the
challenges facing actual nuclear power systems. It is written at an undergraduate
level,butshouldalsobeusefultopracticingengineersandscientistsaswell.