Exergy analysis of heating, refrigerating and air conditioning : methods and applications

391 Pages·2015·10.53 MB·English

by  Dinçer

Exergy Analysis of Heating,
Refrigerating, and Air Conditioning
Exergy Analysis of Heating,
Refrigerating, and Air
Conditioning
Methods and Applications
Ibrahim Dincer and Marc A. Rosen
AMSTERDAM (cid:129) BOSTON (cid:129) HEIDELBERG (cid:129) LONDON (cid:129) NEW YORK (cid:129) OXFORD
PARIS (cid:129) SAN DIEGO (cid:129) SAN FRANCISCO (cid:129) SINGAPORE (cid:129) SYDNEY (cid:129) TOKYO
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Acknowledgments
The contributions of several graduate students are gratefully acknowledged,
including Canan Acar, Sayantan Ghosh, Monu Malik, Farrukh Khalid, and
FahadSuleman.Inparticular,wethankCananAcarforreviewingandrevising
several chapters and checking for consistency.
Inaddition,somematerialscomingfromMohammedAl-Ali,RezaSoltani,and
Abdullah Al-Zahraniare acknowledged.
Last but not least, we warmly thank our wives, Gulsen Dincer and Margot
Rosen, and our children, Meliha, Miray, Ibrahim Eren, Zeynep, and Ibrahim
EmirDincerandAllisonandCassandraRosen.Theyhavebeenagreatsource
ofsupport and motivation.
Ibrahim Dincerand Marc A. Rosen
July2015
ix
Preface
Thisbookfocusesonapplicationsofexergymethodstotheheating,refrigerat-
ing,andairconditioningindustriesandtheprimarytechnologiescomprising
them,withtheaimofprovidinganenhancedunderstandingofthebehaviors
ofsuchsystemsandbettertoolsfortheirimprovement.Heating,refrigeration,
andairconditioningprocessesareveryimportantenergytechnologiesinmost
countries and are often responsible for a significant portion of their energy
utilization. Thus, it is beneficial to consider all available tools in efforts to
improvedesigns,intermsofefficiency,environmentalperformance,econom-
ics, and other factors.
Exergyanalysisrepresentsarelativelyrecentandexcitinginnovationinthermo-
dynamicsandenergysystems.Asamethodthatusestheconservationofmass
andconservationofenergyprinciplestogetherwiththesecondlawofthermo-
dynamics for the analysis, exergy analysis helps in the design, optimization,
andimprovementofenergysystemslikeHVAC.Theexergymethodisauseful
toolforfurtheringthegoalofmoreefficientenergyresourceuse,foritenables
thelocations,types,andmagnitudesofwastesandlossestobeidentifiedand
meaningfulefficienciestobedetermined.Exergymethodshavereceivednota-
bleattentiononlyoverthelastfewdecades.Althoughthatattentionhasgrown
during that period, it has remained somewhat limited and comprehensive
applicationsofexergyanalysisintheheating,refrigeration,andaircondition-
ing industriesremainneeded.
Thebookseekstodescribecomprehensivelytheapplicationofexergymethods
to heating, refrigerating, and air conditioning systems, so as to aid in their
improvement. In doing so, the book containseight chapters. The relationsof
the material to building energy systems and their management are stressed
throughout.
Chapter1describesenergyandexergymethodsandhowtheyareusedtoassess,
design,andimprovetechnologiesandsystems.Fundamentalthermodynamic
principles areexplainedand analysismethodologies basedonexergyare cov-
ered in depth. In addition, extensions of these exergy-based methods to xi
xii Preface
environmental,economic,andsustainabilityassessmentsarecovered.Topro-
videabroadercontext,theroleofheating,refrigerating,andairconditioningin
regional systems like countries is discussed, including relevant energy, and
exergy perspectives.
InChapter2,energyandexergyanalysesofbasicheating,refrigeration,andair
conditioningtechnologiesandsystemsarepresented.Includedareapplications
ofexergyanalysistothecomponentscomprisingheating,refrigerating,andair
conditioning, as well as psychrometric processes and overallsystems.
Chapter3,Chapter4,Chapter5,andChapter6focusonarangeofindustrial
systems and applications of heating, refrigeration, and air conditioning.
Chapter3focusesontheuseofexergymethodsinindustrialheatingandcool-
ingandthediverserangeofprocessesthatcanbeusedforthoseactivities.Heat
pump systems are introduced but are examined in much greater depth in
Chapter 4. Cogeneration, trigeneration, and multigeneration, as well as inte-
grated energy systems and district heating and cooling, are covered in
Chapter 5. Chapter 6 describes how exergy methods are applied to heat and
coldstoragesystems,coveringtherangeofsuchtechnologiesthatfindapplica-
tions in buildings.
InChapter7,buildingHVACsystemsbasedonrenewableenergyaredescribed
andseveralcasestudiesareconsideredforillustration.Theutilizationofrenew-
ableandsustainableenergyinplaceofconventionalenergyresourceslikefossil
fuelsisanimportantextensionofthematerialintheprecedingchapterssince
we feel that renewable and sustainable energy systems represent the future of
energy systems in general and for heating, refrigeration, and air conditioning
in particular.
In Chapter 8, several illustrations are described of exergy-based methods for
improving heating, refrigeration, and air conditioning systems. The methods
coveredincludedesignforresponsibleenergyandenvironmentmanagement,
lifecycleassessment,energyretrofits,andenergysubstitution,thestrategicinte-
gration of energy systems, and the allocation of environmental emissions.
ThesearelinkedtothematerialinChapter7bylinkingthemtotheutilization
of renewableand sustainableenergy.
Incorporated throughout are many illustrative examples and case studies,
which provide the reader with a substantial learning experience, especially in
terms of practicalapplications.
Theappendixescontainunitconversion factorsandtablesandchartsofther-
mophysicalpropertiesofvariousmaterialsintheInternationalSystemofUnits
(SI). A glossaryof exergy-related terminology is also provided.
Preface xiii
Referencesareincludedtodirectthereadertosourceswheremoredetailscanbe
foundandtoassistthereaderwhoissimplycurioustolearnmore.Therefer-
ences can also help identify information on topics not covered comprehen-
sively in the book.
Asaresearch-orientedtextbook,thisvolumeincludestheoreticalandpractical
featuresoftennotincludedinsolelyacademictextbooks.Thisbookismainly
intended for use by advanced undergraduate or graduate students in several
engineering and nonengineering disciplines and also as an essential tool for
practitioners in HVAC disciplines. Theory and analysis are emphasized
throughout this comprehensive book, reflecting new techniques, models,
andapplications,togetherwithcomplementarymaterialsandrecentinforma-
tion.Coverageofthematerialisextensive,andtheamountofinformationand
datapresentedissufficientforadvancedcoursesrelatedtoheating,cooling,and
airconditioning—andadvancedtechnologiesbeingappliedintheseareas—or
asasupplementforcoursesonappliedthermodynamics.Webelievethatthis
bookwillbeofinteresttostudentsandpractitionersandindividualsandinsti-
tutions who are interested in exergy and its applications to heating, cooling,
andairconditioningaswellasthevariousnewtechnologiesandmethodsthat
areincreasinglyfindinguseinthese areas.Thisvolume isalsoavaluableand
readablereferenceforanyonewhowishestolearnaboutexergymethodsand/
or advanced heating, cooling,and airconditioning.
Wehopethisbookallowsexergymethodstobemorewidelyappliedtoheat-
ing,refrigerating,andairconditioningindustriesandboththetraditionaland
new technologies being applied in them. The book thereby provides an
enhancedunderstandingofthebehaviorsofheating,refrigerating,andaircon-
ditioning systems and enhanced tools for improving them. By exploiting the
benefits of applying exergy methods to these systems, we believe they can be
mademoreefficient,clean,andsustainableandhelphumanityaddressmany
ofthe challenges it faces.
Ibrahim Dincerand Marc A. Rosen
July2015
CHAPTER 1
Exergy and its Ties to the Environment,
Economics, and Sustainability
1.1 INTRODUCTION
Heating,refrigeration,andairconditioningprocessesaretreatedasimportant
energy technologies in most countries and are often responsible for a signi-
ficantportionoftheirenergyutilization.Applyingexergymethodstotechno-
logies for the heating, refrigerating, and air conditioning can provide a
better understanding of their behaviors and enhanced tools for improving
them.Thisuseofexergyanalysisnotonlyisadvantageousbutalsoisprudent,
sinceitisusefultoconsiderallavailabletoolsineffortstoimprovedesigns,in
termsofefficiency,environmentalperformance,economics,andotherfactors.
Exergy analysis represents a recently rediscovered and exciting innovation in
thermodynamics and energy systems. Exergy methods, basic to enhanced
and combined models, have received notable attention only over the last
few decades. Although such attention has grown during that period, it has
remainedlimitedandapplicationsofexergyanalysisintheheating,refrigera-
tion, and air conditioning industries, although they have increased notably,
wouldbenefitfromanenhancedfocusandaconsolidationoftheinformation.
The applications of exergy methods to heating, refrigerating, and air
conditioning systems are described in a detailed and comprehensive manner
inthisbook,withtheintentofenhancingunderstandingandaidinginprocess
assessments and improvements.
Thebookstartsbydescribingenergyandexergymethodsandhowtheyareused
toassess,design,andimprovetechnologiesandsystems.Fundamentalthermo-
dynamicprinciplesareexplainedandanalysismethodologiesbasedonexergy
arecoveredindepth.Inaddition,extensionsoftheseexergy-basedmethodsto
environmentalassessmentsandeconomicevaluationsarecovered.Toprovide
a broader context, the role of heating, refrigerating, and air conditioning in
regional systems like countries is discussed, including relevant energy and
exergyperspectives.
1
ExergyAnalysisofHeating,Refrigerating,andAirConditioning.http://dx.doi.org/10.1016/B978-0-12-417203-6.00001-6
©2015ElsevierInc.Allrightsreserved.
2 CHAPTER 1: Exergy and its Ties to the Environment, Economics, and Sustainability
Next, energy and exergy analyses of basic heating, refrigeration, and air
conditioningtechnologiesandsystemsarepresented.Includedareapplications
of exergy analysis to the components comprising heating, refrigerating, and
air conditioning, as well as overall systems. A diverse range of processes are
considered, including industrial heating and cooling, drying, building energy
management, cogeneration and trigeneration, district heating and cooling,
and thermal storage. Measures for improving heating, refrigeration, and air
conditioning systems are also described. Renewable and sustainable energy
systems are covered throughout not only because of their expanding usage
but also because they likelyrepresent the future of energy systems.
Thebookclosesbydescribingandassessingexergy-basedmethodsforimprov-
ingheating,refrigeration,andairconditioningsystems.Themethodscovered
includedesignforresponsibleenergyandenvironmentmanagement,lifecycle
assessment,energyretrofits, and energy substitution.Thelatterisextended to
the utilization of renewable and sustainable energy in place of conventional
energyresourceslike fossil fuels.
1.2 WHY EXERGY?
Energyuseispervasiveinlife,andthereisastrongrelationbetweenenergyand
prosperity. Throughout much of history, the emergence of civilizations has
beencharacterizedbythediscoveryandeffectiveapplicationofenergytohelp
meet society’s needs. The desire of people to sustain and improve their well-
beingispossiblythebiggestdriverofthegrowthinworldwideenergydemand.
Therefore,meetingthedemandforenergyservicesinaclean,efficient,secure,
and reliableway is animportant challenge.
Energy analysis is the traditional method of assessing the way energy is used
inoperations(e.g.,physicalorchemicalprocessingofmaterials,heattransfer,
and energy conversion). Energy analysis is based on the first law of thermo-
dynamics (FLT) and usually entails performing energy balances and evaluat-
ing energy efficiencies. The FLT embodies the principle of conservation of
energy, which states that, although energy can change form, it can be neither
created nor destroyed. However, this law provides no information about the
direction in which processes can spontaneously occur, that is, it does not
explain reversibility aspects of thermodynamic processes. An energy balance
also cannot explain the degradation of energy or resources during a process
and does not quantify the usefulness or quality of energy and material quan-
tities(e.g.,input,product,andwasteflowsforasystem).TheFLTprovidesno
information about the inability of any thermodynamic process to convert
heat fully into mechanical work or any insight into why mixtures cannot
1.2 Why Exergy? 3
spontaneously separate or unmix themselves. Another principle to explain
these phenomena and to characterize the availability of energy is required
to do this.
TheexergymethodofanalysisovercomesmanyofthelimitationsoftheFLT.
TheconceptofexergyisbasedonboththeFLTandthesecondlawofthermo-
dynamics (SLT). Exergy analysis clearly indicates the locations, nature, and
causesofenergydegradationinaprocessandthereforecanhelpimproveapro-
cessortechnology.Exergyanalysiscanalsoquantifythequalityofenergydur-
ing heat transfer. The primary aim of exergy analysis is usually to provide
meaningful efficiencies(i.e.,exergyefficiencies)andthecausesandtruemag-
nitudes ofexergylosses.
Itisimportanttodistinguishbetweenexergyandenergyinordertoavoidcon-
fusionbetweenexergyanalysisandtraditionalenergy-basedmethodsofanal-
ysis and design. Table 1.1, which compares energy and exergy in a general
manner, can help in making such a distinction. Energy flows into and out
of a system with mass flows, heat transfers, and work interactions (e.g., work
associated with shafts and piston rods). Energy is conserved, in line with the
FLT. Exergy, although similar in some respects, is different. It loosely repre-
sentsaquantitativemeasureoftheusefulnessorqualityofanenergyormate-
rial substance. More rigorously, exergy is a measure of the ability to do work
(or the work potential) from a quantity or flow (mass, heat, and work), in a
specifiedenvironment.Akeyattributeofexergyisthatitpermitscomparisons
on a common basis of quantities (inputs and outputs) of different types.
Table1.1 GeneralComparisonofEnergyandExergy
Energy Exergy
(cid:129) Dependentonpropertiesofquantity(e.g.,matterand (cid:129) Dependentonbothpropertiesofquantity(e.g.,matter
energy)andindependentofpropertiesofareference andenergy)andpropertiesofareferenceenvironment
environment
(cid:129) Nonzeroinvaluewheninequilibriumwiththe (cid:129) Zeroinvaluewhenatthedeadstate,thatis,incomplete
referenceenvironment equilibriumwiththereferenceenvironment
(cid:129) Conservedforallprocesses,thatis,canbeneither (cid:129) Conservedforreversibleprocessesandnonconserved
destroyednorproduced forrealprocesses,thatis,canbeneitherdestroyednor
producedinareversibleprocessbutisalwaysdestroyed
(consumed)inanirreversibleprocess
(cid:129) Appearsinmanyforms(e.g.,kineticenergy,potential (cid:129) Appearsinmanyforms(e.g.,kineticexergy,potential
energy,work,heat)andismeasuredinthatform exergy,work,thermalexergy)andismeasuredonthe
basisofworkequivalentorabilitytoproducework
(cid:129) Ameasureofquantity,butnotquality (cid:129) Ameasureofquantityandquality
(cid:129) BasedontheFLT (cid:129) BasedonacombinationoftheFLTandtheSLT