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Preface

When reviewing, or contemplat ing wri t ing, a textbook on engineer ing thermodynamics , i tis necessary to ask: what does this book offer that is not already available? The author hastaught thermodynamics to mechanical engineer ing s tudents , a t both undergraduate andpost-graduate level , for 25 years and has found that the exist ing texts cover veryadequately the basic theories of the subject . However, by the final years of a course, and atpost -graduate level , the mater ia l which i s presented i s very much inf luenced by thelecturer, and here i t is less easy to f ind one book that covers al l the syllabus in the requiredmanner . This book a t tempts to answer that need, for the author a t leas t.The engineer i s essent ia lly concerned wi th manufactur ing devices to enable tasks to be

preformed cos t ef fect ively and ef f ic ient ly . Engineer ing has produced a new generat ion ofautomatic 's laves ' which enable those in the developed countries to maintain their l i festyleby the consumpt ion of fuels ra ther than by manual labour . The developing countr ies s t i l lre ly to a large extent on 'man pow er ' , but the pace of develop men t i s such that the wholeworld wishes to have the machines and qual i ty of l i fe which we, in the developedcountries, take for granted: this is a major challenge to the engineer, and part icularly thethermodynamicist . The reason why the thermodynamicist plays a key role in this scenariois because the methods of conver t ing any form of energy into power i s the domain ofthermodynamics : a l l of these processes obey the four laws of thermodynamics , and thei ref f ic iency is cont rol led by the Second Law. The emphasis of the ear ly years of anundergraduate course i s on the F i rs t Law of thermodynamics , which i s s imply theconservat ion o f energy; the F i rst Law does not g ive any informat ion on the qual i ty of theenergy. I t is the ho pe o f the author that this text wil l introduce the conc ept of the q uali ty ofenergy and help future engineers use our resources more ef f ic ient ly . I ronical ly , some ofthe larges t demands for energy may come f rom cool ing (e .g . ref r igera t ion and a i r -condit ioning) as the deve loping countries in the tropical regi ons bec om e wea lthie r - thismight require a more bas ic way of consider ing energy ut i l i sa t ion than that emphasised incurrent thermodynam ic texts . This book a t tempts to in t roduce bas ic concepts wh ich shouldapply over the whole range of new technologies covered by engineer ing thermodynamics .I t considers new approaches to cycles, which enable their irreversibil i ty to be . taken intoaccount ; a deta i led s tudy of combust ion to show how the chemical energy in a fuel i sconverted into thermal energy and emissions; an analysis of fuel cells to give anunders tanding of the di rect convers ion of chemical energy to e lect r ica l pow er ; a deta i leds tudy of proper ty re la t ionships to enable more sophis tica ted analyses to be m ade of both

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high and low temperature plant; and irreversible thermodynamics, whose principles mighthold a key to new ways of effic iently converting energy to power (e .g . solar energy, fuelcells) .The great advances in the understanding and t e a c h i n g of the rm odynam ics came rap id lytowa rds the end of the 19 th century, and i t was not u nti l the 1940s that these wereemb odied in the rmodynam ics tex tbooks fo r mechan ica l eng ineers . Som e of the approachesused in teaching thermodynamics st i l l contain the assumptions embodied in the theories ofheat eng ines without explic it ly recognising the l imita tions t hey impose. I t w as the desire toremove some of these shortcomings, together with an increasing interest in what l imits thee ff ic iency o f the rmodynamic dev ices , tha t led the au thor down the pa th tha t hasculm inated in this text.I am sti l l a strong believer in the pedagogical necessity of introducing thermodynamicsthrough the tradit ional route of the Zeroth, First , Second and Third Laws, ra ther thana t tempt ing to use the S ing le .Axiom Theorem of Ha tsopoulos and Keenan , o r The Law ofS tab le Equi l ib r ium of Haywood . While bo th these approaches enab le the rmodynamics tobe developed in a logical manner, and l imit the re liance on cyclic processes, theirunderstanding bene fits from years of experience - the one thing students are lacking. Ihave structured this book on the conventional method of developing the subject . The otherdilemma in developing an advanced level text is whether to introduce a significant amounto f statistical thermodynamics; since this subject is re la ted to the particula te nature ofmat te r , and most ensinee rs dea l wi th sys tems fa r f rom reg ions where molecu la r mot io~ tdominates the processes, the majority of the book is based on equi l ibr ium ther .modynamtcs; which concen tra tes on the macroscop ic na tu re o f sys tems. A few examplesof sta tist ical thermodynamics are introduced to demonstra te certa in forms of behaviour,but a full understanding o f the subject is not a requirem ent o f th e text.The book con ta ins 17 chap te rs and , whi le th is m igh t se em an excessive number , theseare of a size where they can be readily incorporated into a degree course with a modularstructure . Many such courses will be based on two hours lecturing per week, and thismeans tha t most o f the chap te rs can be p resen ted in a s ing le week . W orked examples a reincluded in most of the chapters to i l lustra te the concepts being propounded, and thechap te rs a re fo l lowed by exerc ises . Some o f these have bee n deve loped f rom tex ts whichare now no t ava i lab le (e .g . Benson , Haywood) and o the rs a re based on examina t ionquestions. Solutions are provided for a l l the questions. The properties of l imes have beender ived f rom po lynomia l coeff icien ts pub l ished by B enson : a l l the pa ramete rs quo ted havebeen evaluated by the author using these coeffic ients an d equ ation s pub lished in the text -this means that a ll the values are se lf-consistent, wh ich is n ot the case in a ll texts. Som e ofthe combust ion quest ions have been so lved us ing compute r p rograms deve loped a tUM IST, and these a re a l l based on these gas p roper ty po lyno mia ls . I f the reader uses o therdata , e .g . JANAF tables, the solutions obtained might differ sl ightly from those quoted.Engineering thermodynamics is basically equi l ibr ium thermodyn amics , although for thefirst two years of the conven tional undergradu ate course th ese word s are used but not oftendef ined . Much of the the rmodynamics done in the ea r ly yea rs o f a course a lso re l ie sheavily on reversibility, witho ut explic it consideration of the effects of irreversibili ty . Yet,if the performance of therm odyn am ic devices is to be im pro ved , i t is the irreversibil ity thatmust be tackled. This book introduces the effects of trreversibil i ty through considerationsof availabil i ty (exergy), and the concept of the endoreversible engine. The thermaleffic iency is re la ted to that of an ideal cycle by the ra tional effic iency - to demons tra tehow closely the performance of an engine approaches that of a reversible one. I t is a lso

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shown that the Carn ot effic iency is a very art if ic ial yardstick against which to c om pare realengines: the internal and ex ternal reversibili t ies imposed by the cycle m ean th at i t producesze ro power a t the ma xim um ach ievab le e f fic iency . The approach by C urzon and A hlbornto de f ine the e f f ic iency o f an endorevers ib le eng ine produc ing m aximum pow er ou tpu t isintroduced: this shows the effect of externa l irreversibility. This analysis a lso introducesthe concept of entropy generation in a man ner readily understandable by the eng /neer; th isconcept is the cornerstone of the theories of irreversible thermodynamica which a re a t theend o f the text.W hilst the laws o f the rm odynam ics Can be deve loped in i so la t ion f rom conside ra t ionof the property re la tionships of the system under consideration, i t is these re la tionshipsthat enable the equations to be closed. Most undergradua te tex ts a re based on theeva lua t ion o f the f lu id p roper t ie s f rom the s imple pe rfec t gas law, o r f rom tab les andcharts. While this approach enables typical engineering problems to be solved, i t does notg ive much ins igh t in to some of the phenomena which can happen under ce r ta inc i rcumstances . For example , i s the spec i f ic hea t a t constan t vo lume a func t ion o ftempera tu re a lone fo r gases in ce r ta in reg ions o f the s ta te d iagram7 Also , why is theassumpt ion o f cons tan t s tagna t ion , o r even s ta t ic , tempera tu re va l id fo r f low of a pe rfec tgas th rough a th ro t t le , bu t never fo r s team? An unders tand ing o f these e f fec ts can beob ta ined by examina t ion o f the more complex equa t ions o f s ta te . Th is immedia te lyenab les methods o f gas l iquefac t ion to be /n t roduced .An importan t a rea o f eng ineer ing the rmodynamics i s the combust ion o f hydrocarbonfuels. These fuels have formed the driving force for the improvement of l iv ing standardswhich has been seen over the last century, but they are presumably finite , and areproducing levels of po llution that are a constant challenge to engineers. A t presen t, there isthe threat of global warming due to the build-up of carbon dioxide in the a tmosphere: th isrequ ires m ore e f f ic ien t eng ines to be p roduced , o r fo r the ca rbon -hy dro gen ra t io in fue lsto be reduced. Both of these are major challenges, and while CaUfomia can legisla te forthe Zero Emissions Vehicle (ZEV) this might not be a worldwide solution. I t is sa id thatthe ZEV is an e lec t r ic ca r runn ing in Los Ange les on power p roduced in Arizona l -obviously a case of exporting pollution ra ther than reducing i t . The real challenge is notwha t is happen ing in the W est , a l though the energy consump t ion o f the USA is p rod ig ious ,but how can the aspira tions of the East be met. The combustion technologies developedtoday will be necessary to enable the Newly Industria l ised Countries (NICs) to approachthe leve l o f energy consumpt ion we en joy . The sec t ion on combust ion goes fu r the r thanmany general textbooks in an a ttempt m show the underlying general principles that affectcombustion, and i t in troduces the interaction between thermodynamics and fluidmechanics which is so important to achieving c lean and effic ient combustion. The finalchapter introduces the thermodynamic principles of fuel cells, which enable the directconversion of the Gibbs energy in the fuel to e lectrical power. Obviously the fuel cellcould be a major contributor to the production of 'c lean ' energy and is a goal for which i tis worth a im /ng.Finally , a section is included on irreversible thermodynamics. This is there partly as aninte llectual challeng e to the reader, but a lso because i t in troduces concepts tha t m ight gainmore importance in assess ing the pe rfo rmance o f advanced fo rms of energy convers ion .For examp le , a l though the fuel cell is basically a device for converting the Gib bs energy ofthe reactants into e lectrical energy, is i ts effic iency compromised by the thermodynamicsof the steady sta te that are taking place in the cell? Also, will photo-volta ic devices belimited by phenomena considered by irreversible thermodynamics?

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x ii PrefaceI have t aken the generous adv ice o f Dr Joe Lee , a co l l eague in the Deparunen t o f

Chemis t ry , UMIST, and modi f i ed some o f the word ing o f the o r ig ina l t ex t to b r ing i t inl ine wi th more m odern chemica l ph raseo logy . I have rep laced the r if le s Gibbs f ree ene rgyand He lmhol tz f r ee ene rgy by Gibbs and He lmhol tz ene rgy re spec t ive ly : th i s shou ld no tcause any p rob lems and i s more log ica l than inc lud ing the word ' f r ee ' . I have bowed , wi thsome reservat ions , to us ing the in ternat ional ly agreed spel l ing sulfur , which again shouldno t cause p rob lems . Pe rhaps the mos t d i f f i cu l t concep t fo r eng inee r s wi l l be therep lacement o f the t e rms 'mo l ' and ' km ol ' by the t e rm ' am oun t o f subs tance ' . T h i s hasbeen com mo n p rac t i ce in chem is try fo r ma ny yea r s , and sepa ra te s the genera l concep t o f aquan t i ty o f m a t te r f rom the un i ts o f tha t quan t ity . For ex am ple , i t i s com m on to t a lk o f amass o f substance wi thou t de f in ing w he the r it is in g ram s , k i log ram s , pound s , o r wha teve rsys tem of un i t s i s appropr ia te . The use o f the phrase ' amoun t o f subs tance ' has the samegenera l i s ing e f fec t when dea l ing wi th quan t i f i e s based on molecu la r equ iva lences . Theterm mol wil l s t i l l be re ta ined as the adject ive and hence molar enthalpy is the enthalpy perun i t amoun t o f subs tance in the appropr iate un i ts ( e .g . k J /m ol , kJ/kmol, B m / l b - m o l , e t c ).

I wou ld l ike to acknowledge a l l those who have he lped and encouraged the wr i t ing o fth is text . F irs t , I would l ike to acknowledge the inf luence of a l l those who a t tempted toteach me the rmodynamics ; and then those who encouraged me to t each the sub jec t , inpa r t i cu la r J im P icken , F rank Wal lace and Rowland Benson . In add i t ion , I wou ld l ike toacknowledge the encouragement to deve lop the ma te r ia l on combus t ion which I r ece ivedf rom Roger Green dur ing an Ersk ine Fe l lowsh ip a t the Unive r s i ty o f Can te rbury , NewZea land . Second ly , I wou ld l ike to thank those who have he lped in the p roduc t ion o f th i sbook by read ing the t ex t o r p repa r ing some o f the ma t i~r ia l. Am ong s t these a re E d Mo ses ,Marcus Dav ies , Poh Sung Lob , Joe Lee, Richard Pea r son and John Hor lock ; wh i l s t theyhave read pa r ts o f the t ex t and p rov ided the i r comm ents , the r e spons ib i li ty fo r the accuracyof the book l i e s en t ir e ly in m y hands. I wou ld a l so l ike to ackn ow ledge m y sec re ta ry , M rsP Shepherd , who d id some o f the typ ing o f the o r ig ina l no tes . F ina l ly , I mus t thank mywife , Veron ica , fo r pu t t ing up wi th l ack o f ma in tenance in the house and ga rden , andmany even ings spen t a lone whi le I concen tra ted on th i s w ork .

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