Applied Thermodynamics MAE 321
Popular in Course
Popular in Mechanical Engineering
This 34 page Class Notes was uploaded by Ardith Gutmann on Saturday September 12, 2015. The Class Notes belongs to MAE 321 at West Virginia University taught by Greg Thompson in Fall. Since its upload, it has received 51 views. For similar materials see /class/202648/mae-321-west-virginia-university in Mechanical Engineering at West Virginia University.
Reviews for Applied Thermodynamics
Report this Material
What is Karma?
Karma is the currency of StudySoup.
You can buy or earn more Karma at anytime and redeem it for class notes, study guides, flashcards, and more!
Date Created: 09/12/15
MAE 321 Applied Thermodynamics Thermodynamics An Engineering Aggroach 6th edition Yunus A cengel and Michael A Boles The Following Slides Are From the Instructor39s Section ofthe McGraw Hill Web Site and Have Been Modified forThis Course March 9 2009 Lecture Chapter 10 Vapor and Combined Power Cycles Objectives Evaluate the performance of gas power cycles for which the working uid remains a gas throughout the entire cycle Analyze vapor power cycles in which is alternately vaporized and condens Analyze power generation coupled with process heating called cogeneration Investigate ways to modify the basic Rankine vapor power cycle to increase the cycle thermal ef ciency Analyze the reheat and regenerative vapor power the working uid ed Analyze power cycles that consist of two separate cycles known as combined cycles and binary cycles THE CARNOT VAPOR CVCLE n mm A s m sunabk Men M We ewes aeeeuse Vvace5512 mm M hemlvans ev messes mm Phasesvskns semen was he memmempemne m equot be used n we We e m c Vannine Vmcess 41Ms m yummy deswn camvvessavlhm hand es w Phases Yhecyme m m snm senene smen reenm semr vn compressunm ex reme ymgh prasnresene Smhermm merensver a eenemewaseres 2 smherma hea smagvam mm Camm vapnv cvdes RANKINE CVCLE THE IDEAL CVCLE FOR VAPOR POW Manvnnhe mmamcamwes assume ed Mn We Camm was an be ehmmaled nvsupevneannmne aeam m We neuev and eeneensng n cummele v n We eeneensev rne ode m1 vesuus sme RanhnE cycle Wnnn mne mea Wde vm vapnv newev mama rne mea Rankme Cvde eees nm We ve anv Wema wevevsnumes n mqu nneew n nun mm mm M new nmvnm u Mn enmmn mmne mm m hen M menu rne snnme mea Rankme Cvde Energy Analysis onne Ideal Rankine Cycle S eadvr nwenevngualmn n was n l Hmm yenHm e syn n luvmum m n n n rnnnnm m r m Themevma emueno can be Hemmer asthe valm enne avea amused bvme cvde en a sdwagvam mne avea uneev me hearadmunn pmeess DEVIATIDN OF ACTUAL VAPOR POWER CYCLES FROM IDEALIZED ONES rne aaoar vapm pawv was away rnn the roear Rankme was as a vesun m wvevevsrh mes rn vavmus mnponens mm rrrnron and heat rossmne sumundmgs are the NM camman soonesorrrrerersrnrrrnes I MNWW mm IE a Devrmmn m anoar vapm power cyc e non the raear Rankme were to Me enact or Pump andmvhme rrreversnrmres an the roear Rankme cvde ow CANWE INCREASE THE EFFICIENCY OF THE L 7 rne hasu raea bemnd au the madmcmmnsm rnaease the thema emmency m a pavvev a are rsme sne muses the were temperature me heat s rransrerrea n the wurkmg urd n the harm 27 decrease the arerege Lowering khe Condenser Pressure Lowers T MM rs take advamage Mme rnare ased rme mndensevs m ean Pav evmamsusua vapevmev e avvevhmMathrspvessmedepenmnganme tempevamve onne ooorrne medmm sme steel Lav enngmecandensev Pvessuve maeasesthe mmstme camem m r e seen a nerrnar stagesonnemrnrne rne enact m Wav enngme V candensev Pvessuve an the raear Rankme were Superheating the Steam to High Temperatures Increases rWM Burn the net Wuvk and ma mpm rnerease as a resun ursuperneanng Tne uvevaH e ec rs an rnerease rn nerrnar ewereney srnee We avevage rnereases Supevheatmg m mghenempevamves s1earn a the mvbme errtrwnren rs desrrame Tne mmpevamve rs hmned by Yhee eamwpememrngme rnerauurgrearennsroerannnsPresenny steammmghevtempevatmes nenrgnes1srearnrernneramreaunweo Increasing rne Eoiler Pressure Increases rmghm Fa npernme havemema emenmes m sham my nudan man s rne even m naeesngme bm ev THE IDEAL REHEAT RANKINE CVCLE 1 Supemem the steam m VEW mymempevamves u s hmned metangme a 7 H x rne smg e reheat n a madam Pav ev P amxmpmvesmeEmeemmencvhvua v 5 was empevmme at Wmch heat stvansvened tathesteam vevage tempevamve mmer m s a e 21 mmmvemem m emmency nan the secand veheat s sham nanannm Wm rne avevage empevamve at rne vehea empevamves ave vevvcmse quotWSW messes W m equa a the mvbme me empevmme WW 239 quotmm WES 5 rne ammmm renem Pvessuve s sham anemunn anne maxmmm Eve s Pressuve THE IDEAL REGENERATIVE RANKINE CVCLE rwm We we pen a he heeeeuuman pmcess m We hwevmkes wane 3 exchangev Wneve heat stvansvened m v atwew mvwewevams We steam a We Veedvvalev emhev by mxmgmmnmusueemsap n dased Veedv alev hemevs Open Feedwater Heaters m m mum 1mg smaH ml y ve rmxmg ember mu m rm n 7 mm 1 memmme eaves quot 39 W m 39 m m thepump Mean as uvatedhqmda he u H mWMMMM We hemev as heatev PvessA We mea Vegenemwe Rankme web w an apen Veedvvalev hemev closed Feedwater Heaters We clam teemnu hellu w Wde heat shansvened m We extvaded steam a We Veedv alev Mham anv mxmg takmg mace Me My eyeems nawcan be m dmevem Pvessues smeemma m mx We mea vegenevmwe Rankme We vwm a dased veeumey heatev We dased Veedv alev hemevsave Mme cammex because aHhe Mema mmer 21 menemsmyeyemmeexpenswe Hemyemennemse Veedvmev hemevs e Wesse edwe me theme eyeems ave nm euweem be m wed mm Heweven mused Veedv alev heme da nm veewe a a 312 Pump Mes2h may me We waded steam and he Veedv alev an be at dmerem Press es open Veedv alev Askam mm mm m Wequot end Nee c ased mamam healevs eamhemeh hav evev apump sreqme a W W hand m m m mm Veedv alev hemevs SECONDLAW ANALVSIS 0F VAPOR POWER CVCLEs er destmdmn m e steadyenawsvslem e emwmme v e 4 a Steadyenaw anee r r J xmetaneexn w Emvgydeslmdmnmawc e u Favacw emhhemtvansmv my W a sum2 and a w y A sueem exevev Aseeun awana yswsulvapuvpuwevcyc esvevea swhevem avgeg mevevswbmues Dam and Wham m 51m mpvuvemems COGENERATION u n my Pmcessh nthesemdusmesxsusua WsuPPhed hvsteam at 5m 7am enmsma zuu39c EnevgvSusua thansvenedtathesteam bv buvmng Baa am namva gee m anmhev me m a mmeee meuenesmm use was ammmls quotW ense a hes sad 7 enshng v mk pmerma a pmeuee Pav ennsteada emngmgam Wes e We 12501 e a mannhm Pmduces e ednc vwm emeemgme Pmcesshea yeewem ems m cenam mdusma pmeesses cagenevmmn mam mm we A sxmme Pvacessrhemmg warquot he pmdudmn m mammary ane useM mm m eneve Cngenull n r v such as Pracess heat and e ednc Pavvev m we we enevey mums Unhzauan n a n mw amen W Mm Mn n 3 n dea steammvbw Jahw quot9 cugenevauun p am he muna anquot 0 Adua cugenevauun p ams mum N i have uuhzaHUMamuvs as mm m mgh as SEWa Sn m2 neeen e nanan p ams have even mghev umzanan Vac uvs Ammes m Wgh demand VDY Pvacess heat an We steam he mmedmthe Pvacessrhemmg unns heat he 12m h ms naae mhnsnsnma vneem mnes eanweahneahe ha ensthmmed hvanexpansmnmpvessuve U ana he dwededm the Pvacessrheatmg unn Maxxmum Pvacess heatmg he veahzed when an We steam eavmg We aanev Passesthmughme wwwan mg ND paw spmduuedmms Whenmeve he na demand vm Pvacess heat an We steam Passesthmugh Memvhme andthe eanaenaev msrmfm andthe eaaenenahan l39mnnl math pevatesasanmmnawseamp A mgenevatmn mam mh mam adyustab e aads Um quot H M gm M m min nanh lr gtmrHv 4 COMBINED GAS VAPOR POWER CVCLES rhe mmmued quest my h ghevmema emuenues has vesmed h vathev mrmvatwe naameahansm canvermana Pawv man s Wmch he mHedthe eamnan gsvlvnr cyEle mum We eamnan cycle enhev auhe wdes executed mdwmua w u naheseneheenna sense a ake advantage anhe ver deswah e chavadenshus auhe gauuvhme owe a Wgh tempevamves andm use We Nah a steam Pav evcvde am 53 camhx eee an cvde Recent devempmems m gauuvhme techrm agv have madame eanahee gas steam cvd vm mdwe e ecarmmca w vev ahea cm mcveasesthe emuencv mham ncveaswgme hmaw cast 3W sequentwn manv newnahen Wants wants an camhmed Dvdes ana manv Mme emne steam av gaswvbme man s ave bemg canvenedm cambmedrcvde paw wants Yhema emuenmeswevSUVeavevepaned Cumbmed gasrsmam puwev mam MAE 321 Applied Thermodynamics Thermodynamics An Engineering Aggroach 6th edition by Yunus A cengel and Michael A Boles The Following Slides Are From the Instructor39s Section ofthe McGraw Hill Web Site and Have Been Modified forThis Course February 9 2009 Lecture Chapter 8 Exergy A Measure of Work Potential Objectives Examine the performance of engineering devices in light of he second law ofthermodynamics De ne exergy which is the maximum useful work hat could be obtained 39om the system at a given state in a speci ed environment De ne reversible work which is the maximum use Jl work that can be obtained as a system undergoes a process between two speci ed states xergy destruction which is the wasted work potential during a process as a result ofirreversibilities De ne he secondlaw ef ciency Develop the exergy balance relation Apply exergy balance to closed systems and control volumes GY ORK POTENTIAL OF ENERGY The useM Wuvk putarma u a gwen amuum Menevgy at same specmed sme s caHed exergy Wh ch s a su caHed the avarabtMuv avariabe energy ethbnum WNHME enwunmem n s m A he dead we We useM svSlem 5 12m A New mm s m ethhvmm Wm Ms enwanmem 5 saw a he aims dead state A Ssfem delivers the WWW mm mm as x undergues a reversrbe Pmcess mm the speci ed mmsme m the state ans enwmnme f mm the dead state m vepresemsme usemwwkpufenma he svslem aims meemeu state and s caHed exevgv 1er my 10 mumm e e r mum We mmemate sumundmgs m a m We mmamhere Bantams a Evamem lane aHhe aw next We W m mm m Exergy Work Potemial Associated with Kinetic and Potential Energy 7 Exergy Mkmebc energy m v m Exergymmemeneygy h k l H Wentm V exer m pmerma enevgv I Vegeeevgd esm mum m enueeneygv meme sew ewe WWW We we a m W3 Memeenegws we 39 hepamanmenevgv manme k 4 canvenedmwuv m eve veversxh eheat engme m a V me u n n u p ufulefulwmmitcmhepmdwsd prme s s mm seem empeeeysss M M y umewusripmcexxbemeenme mm weened we see rmware I u u u e hum quotm memem Ku gnm mm We see emwm ewe meeeseme MW rum m We u SECONDLAW EFFICIENCY m M m x h Wm m heat engmesmal have We see Meme emeem seeene swemeeneWss e We me am mm um devme mauve m M5 Pev39nvm ante ewe 9 mm undev vevevswb e cnnrmmns V quot quot Geneva dehnmun u n m he eeeeyemeney W i s us m 391ng vm we 4 399 Me secnnmawemmemvm natuvauv accumng pmcesses es Wt see u nene We W pmerma es vecnveved Secnnr awemuenw mau vevevswb e names 5 mm EXERGY CHANGE OF A SYSTEM Exergy of leed Mas Monnow or closed System Exergy mm 1 The exergyma specmeu mass m a specmeu aale sme useM Walk m an be Pmduced as me mass undevgnes a vevevsme mncessmme aa e unheenwmnmem w s s r C nse svsmm emvgvpevunn mass When we mnpemes m a svstem ave nm un nvm me exevgv mm svstem s M W The exergyn39a mm memum sa sn a New mm was Walk can be mounted W wuanswemng heannn I x Exergy of a Flow Stream Flow or Stream Exergy Ms 4 7 Judi v Exevgvn nwenevgv 39rr us JIM HI m 9er WWW 35mm v M a W law energwsm HM r useM va mm mm The energy and exergy contents of a a xed mass b a uid stream EXERGY TRANSFER BY HEAT WORK AND MASS Exergy by Heat Transfer Q transfer by neat V wnen w tern perature ts not constant rnot efftctency 77514 T represents tne fractton oftne energytransferred trorn a neat source at temperature Ttnat can be conve ed to Work tn an envtronment at ternperature TD l m quotmtquot ransfer and temperature dtfference H m lm39ut uumnt u M I 0 a k w u quotquotquot t t Exergy Transfer by Work W rtnr tnnn tnt t rrnr ntnn tnnn nr Nutty It 1 t n39 IA u u t Mass contatns energy w my exergy transfer atrn ospneno pressure THE DECREASE 0F EXERGV PRINCIPLE AND EXERGV DESTRUCTION N m wk II IuIIeI I IIII I II II II I I MIINIWIII He II II pIInprIe The exergy are rsalafed sysem Immg a Muses aways decreases m In neIeIIneIeeses and emgy Is destruyedduvmg an anus Pmcess Ms Is WWI as the deans In many nnnclple Exergy Destruc I I I II eII IIIIIsIsIIIzIIIIIIW II uzeIeIsImIIIIIIuII a U IIIIIIIIssIIIIIIIIM gtev v destmyed Is e Pusme amenm anv emeI Pmuessand bemmes zen M e Vevevs bIE Pvacess Emng destvwed VEPvesenIsIhe Inst Wm paIemIeI and Is eIsa caHed We mewMI hstwurk We exevev Change m e svSlem can he neeewe bu he exeng esm mn mnnm EXERGY BALANCE CLOSED SYSTEMS eII eIIIW I 39HH IIIIIM VIIIIII M I IL Memamsms we IWM III m exeng he hemuwgna w m H SVSemandv nfx da bythesvslem ave taken m be m W 39 n n H 1 quot paswequammes a smg hemvamnmaughm haundawmtempevmme n51 mam K EXAMPLES Exagy balance for expansion of steam r m We mvgyhame appheu an the extended mews em mmemme suvmundwgs muse haundavwsa he enwmnmem empevmuve av Tum m c Exergy balance for an arrtank m A N A m ca xr zuaw mm m rm n rwmrmzm R H mm M p 1 195w H 95quot r Yhesamee edanmemwmed tank svsem can he accampmeu w mnsumesan v1 w mka EXERGY BALANCE CONTROL VOLUMES r r u exevgv nesmamn mmquot me the mm we own Exevgv Mans eva mm N am m a mmvm vnmme w mass as we as hea and wow mnsvev Exergy Balance for SteadyFlow Systems Mas cammvammes e nachanves movequot ms mew emw indexewycankms sweu m wms Yheve me aw r anddXCJdtr Wmmms th m Patten The exevgvhansienn a s1eaewnwsvstem s eeua m We exemv a Uansmmm musme enema quot an We Sv em Reversible Work Wm The exevgv ba ance ve a mns mesemed above an be usee m delevmmemevevevswb e wok Wubvsemngmeemvgvde mved equa m zem The vmk wmm mse becamesme revevswb e vmk W N u A s w x u a u m a x M w m The exam nesunvee s zem my my a vevevswb e pmuess and vevevswb e vmk vemesemsme mammum vmk mm m We pmeuemg names such as Names and me mwmmum Walk mm m meansan ames mm as mmmessms Second M w Law Ef ciency of SteadyFlow Devices H s detevmned m MM n r u onmmessm M W mm 7 7 7 Wm We W MW W gt quotwhchambev Aheat emhangevvwlmvw amped H Mdsveams quot M g w in em EXAMPLES WW 9 H 39H E r 39 HUN 7 TUKIHN If Exergy balance for a margmg process 7 x 39 9 31 quot J 7 J quotb lt 93 M p M V A N Q1 T 6 D 6 w J g m I a y j v i my IQ 3 mm 23 4 2m A jonpquwd lt6an Al qm o Vdnwuvv W139 17 34 0 3 juu b 37qu 1341 mswrwlv qu MW ON 7 7 384igt l 2w m H39LLLMQLX 6 1 fl quotW N 3413 N 44k 1 54 Lg to RR W if z h D P 31 167210 a 1 A ag SQW3039001073 2599 5 C H f r I I W FQK9HE 97 12762 TL 39Ea anp170r5 A m f72ofe7 x5 94 4ka 5 mm L 5 er 17041 7 V7 V 2 46119396 727 553 233 W h Me 7 47 2 L0 72087 H793 4T1 L 1 3 Pa 223 quotY 2 530 C kg 3470 gutsha 56 W X i 3 Sm quot1 eke0 5r7 35 CF lg Z 39 35 v5 Swat Hmw 0 M01 2 L Kg 46 720374 09935 Zok7quot 2733 4 ch RQIOIMpx Sco 932 94 1wa smSg 1 65212 11977 09323 Xlo gm lt13 Zoo worriw KM guy omswsgt 23725 W11 I 3A us SM 9 35 w w WW amp 99317 OrLaH lZ 9 3 WWW R O 397 7 7 7 X 9 98 0757 2392 M 55 m 0P5 Pu UV39 4 wk M was a a mon Rah 3 ltx3i5 jifquot La 21 quot0 sea 43 01924729 g7 4AQLESQ EZ E 1 lt43 wm ng LA 0 34795 72739327 53 Qf 33amp79 77 49gt 12 quot i39 lt5 U C 07 QJ QL72037H2 WE a we rms 727 w Wt JDOCC W OKPPV 4 marmie a NON 10 V39mw i WI wn Mm Q4 1 MN U34 m mm be11637 an u bl W OPECr7312 Ta 7537 Aw Clt 45 La Next m M r EMQqA szlcum 0A A694 ExtCw MU9F 5FLcuj 04364 sst v1 v54 Lg Lb M w 1 213 111 0P T9 7 my cam 243 WM L L a 2 CPCI7T39T a ET T j 39 M3 4 L QM V5 p 5 4 1 94 391 252 29314 skicl ff n H w i F 5303 K 5 493 f f 2 7aal 11k sum c 13734 81 1 53 N g 8 L 4399 lt71 6P T 3972 M 23 Ir LP W b r Est Eff quot g73quot quot 7s 8oL m 1 was Bria OWNS 83 9W L I nk T hwh Mpg 27 c 48sz 31m 39RaozP4gA Lgf s L 23742 R vim quot4 0 256039s 4 sake 2 E MR 7 MP 2 LLJquot 41W mm 1 D Pp 3 Wf Ma 1 qt w LL oomo Qooo 20 25142 0 5 33 gt GUS 5amp1 2375 7351 a v 55L 3 34991404 395 3202 A 5 3 29531 V w 7 0 53 men 584 Ines 2035355 0 Mam Z isSL Olt2 Cz953 205933 21274 A cfgto 062C IIOO EWrS al 26531 21224603 M0 quot0 30 B73 quot83995quot 5 7 7427 5 26 534 257 5 5279 354 MAE 321 Applied Thermodynamics Thermodynamics An Engineerinq Approach 6th edition by Yunus A Qengel and Michael A Boles The Following Slides Are From the Instructor s Section of the McGraw Hill Web Site and Have Been Modified for This Course April 27 2009 Lecture Chapter 15 Chemical Reactions Objectives Give an oveniew of fuels and combustion Apply the consenation of mass to reacting systems to determine balanced reaction equations Define the parameters used in combustion analysis such as airifuel ratio percent theoretical air and dewpoint temperature Apply energy balances to reacting systems for both steady flow control volumes and fixed mass systems Calculate the enthalpy of reaction enthalpy of combustion and the heating values of fuels Determine the adiabatic ame temperature for reacting mixtures FUELS AND COMBUSTION Fuel Any material that can be burned to release thermal energy Most familiar fuels consist primarily of hydrogen and carbon They are called hydrocarbon fuels and are denoted by the general formula n m39 Hydrocarbon fuels exist in all phases some examples being coal gasoline usually treated as octane Cngagt and natural gas mu l A comparison of me allelnatlv Mai to the liadillunal pitmleum basal luzls used llV ItallS oilaliml Enzvgy uniciit Gasulliie Equivalence kJl Fuzl LlLrgawllliE Gawlllle 31353 1 Light meszl 31m u 95 Heavy lesel 35mm 039 we lquuellcd petioleum gas lmrllanlv plepane 23mm 1 36 Ethanol luv clhyl alcoholl 99420 i 03 Melhalml iol methyl alcoholl Bln i 15 c l nmpmsst natural gas fl lllllllarllv methane at 200 aim is oao 3 94 bl we lllrluellea natural gas Mos qmd hydrocarbon fuels mlllvauly metllauel 490 i as are Omamed from crude on by Wallullwlilm distillation The oxidizer most often used in combustion processes is air Why On a mole or a volume basis dry air is composed of 209 02 781 N2 09 Ar and small amounts of 002 He Ne H2 In the analysis of combustion processes dry air is approximated as 21 02 and 79 N2 by mole numbers 1 kmol 3 376 kmol N 476 kmol air Am 21 02 79 N2 1 kmol 02 376 kmol N2 Each kmol of 02 in air is accompanied by 376 kmol of N2 Combustion is a chemical reaction during which a fuel is oxidized and a large quantity of energy is released The fuel must be brought above its ignition temperature to start the combustion The minimum ignition temperatures in atmospheric air are approximately 260 C for gasoline 400 C for carbon 580 C for hydrogen 610 C for carbon monoxide and 630 C for methane Proportions of the fuel and air must be in the proper range for combustion to begin For example natural gas does not burn in air in concentrations less than 5 or greater than about 15 gt Reaction Reactants chamber gt Products 2 kg hydmgen 16 kg oxygen Hz 0241120 2 kg hydrogen 16 kg oxygen The mass and number of atoms of each element is conserved during a chemical reaction The total number of moles is not conserved during a chemical reaction In a steadyflow combustion process the t enter the reaction chamber are called reactants and the components that exit are called products Airfuel ratio AF is usually expressed on a mass basis and is de ned as the ratio of the mass of air to the mass of fuel for a combustion process II AF I illvl m NM m mass N number of moles M molar mass Fuel air ratio FA The reciprocal of air fuel ratio Fuel 1 k Combustion g chamber Products Air AF 17 18 kg 17 kg The air fuel ratio AF represents the amount of air used per unit mass of fuel during a combustion process THEORETICAL AND ACTUAL COMBUSTION PROCESSES Complete combustion lfall the carbon in the fuel burns to 002 all the hydrogen burns to H20 and all the sulfur ifany burns to 802 Incomplete combustion lfthe combustion products contain any unburned fuel or components such as C H2 CO or OH Reasons for incomplete combustion 1 Insufficient oxygen 2 insuf cient mixing in the combustion chamber during the limited time that the fuel and the oxygen are in contact and 3 dissociation at high temperatures Fuel 11 C02 in CHH quot Combustion 7 H20 Am chamber Excess 02 N2 A combustion process is complete ifall the combustible components ofthe fuel are burned to completion Oxygen has a much greater tendency to combine with hydrogen than it does with carbon Therefore the hydrogen in the fuel normally burns to completion forming HZO Stoichiometric or theoretical al The mInImum amount of an needed for the complete combustion of a fuel Also referred to as the chemcaly correct amount ofar or 100 theoretca aIr Stoichiometric or theoretical combustion The Ideal combustion process durIng thch a fuel Is burned completely WIth theoretIcal aIr cas a h of an In excess of he stoIchIometrIc amount Usually expressed In terms of the stoIchIometrIc an as percent excess aIr or percent theoretca aIr De ciency of air Amounts of an less than the stoIchIometrIc amount Often expressed as percent defIcIency ofar Equivalence ratio The ratIo of the actual fuel aIr ratIo to the stoIchIometrIc fuel aIr ra CH4 20 376N3 4 50 excess aIr 150 theoretIcal aIr CD1 QHVO 7 WNW 200 excess aIr 300 theoretIcal aIr 90 theoretIcal aIr 10 defIcIency of an nn unburned l39ucl no line oxygen in products The complete combustIon process WIth no free oxygen In he products Is called theoretIcal combustIon PredIctIng the composItIon of the products Is relatIvely easy when the combustIon BEFORE process Is assumed to be AFFER complete 100 kPa WIth actual combustIon 25 C 100 kPa processes It Is ImpossIble to 25 C Gas sample predIct the composItIon of Gas sample the products on the basIs of Including C02 without CO the mass balance alone 1 liter Z en a 09 lIter have Is to measure the am unt of each component y col 0 1 In the products dIrectly C01 7 V 7 l 39 Acommonly used devIce to DetermInIng the mole fractIon of the 002 In 39 W g me Orsat gas combustIon gases Is the analyzer Orsat gas analyzer The results are reported on a dry basIs ENTHALPY OF FORMATION AND ENTHALPY OF COMBUSTION Disregarding any changes in kinetic and potential energies the energy change of a syste during a chemical reaction is due to a change in state and a change In chemIcal composItIon All m AENW AE LIIL m Nuch cim gy lwiniml mimgy L m mm lirukcn L39IIL IIIILAI bunt MOLECULE ATOM When the existing chemical bonds MOLECULE re destroyed and new ones are The microscopic form of energy of substance consists of sensi le latent energy Is absorbed or released chemical and nuclear energIes Enthalpy of reaction IIR The difference between the enthalpy ofthe products at a speci ed state and the enthalpy of the reactants at the same state or a complete reaction Enthalpy of combustion IIc It is the enthalpy of reaction for combustion processes It represents the amount of heat released during a steady ow ombustion process when 1 kmol or 1 kg of fuel is burned completely at a speci ed temperature and pressure The enthalpy of formation hf The amount of energy absorbed or released as t component is formed from its stable elements during a steady ow process at a speci ed state point we assIg enthalpy of formation of all stable elements To establish a starting nt e hf Q 393520 kJkmol C01 such as 02 N2 sz Itmul C and C a value of zero gt at the standard 25 C 1 Ml Combustion 1 km 3902 5 reference state o r C d 1 atm I kmol 02 C dm 25 C 1 mm gt 25 C I aim Heating value The amount of heat mh LHV 39 l 0 released when a fuel is burned Q R 2 completely in a steadyflow process and the products are returned to the state of the reactants The Combustion quot 39pma c t39s39 heating value of a fuel is equal to chamber vapor H20 the absolute value ofthe enthalpy of combustion of the fuel Higher heating value HHV When the H20 in the products is in 39739 Products the liquid form Lower heating value LHV When the H20 in the products is in the vapor form HHV LHV milgqu liquid H20 The higher heating value of a fuel is equal to the sum ofthe lower heating value of the fuel and the latent heat of vaporization of the H20 in the products For the fuels with variable composition ie coal natural gas I fuel oil the heating value may be IHHV LHV T quotmm ll n lkI kg It ll determined by burning them directly in a bomb calorimeter chuiing ulm lrl l kJ kg will FIRSTLAW ANALYSIS OF REACTING SYSTEMS 3W1 The energy balance the firstlaw relations developed in Chaps 4 and 5 are applicable to both reacting and nonreacting systems We rewrite the energy balance relations including the changes in chemical energies SteadyFlow Systems 7 l 7 Sensible Llillmlp 71 T I I klMimi enthalpy relative When the changes in kinetic and potential energies are to 25 C 1 atm negligible the steadyflow energy balance for a chemically reacting steady ow system The enthalpy of a chemical Em Em component at a specified state Q t llm l Silll l I lr uHI l llum l EMAl 4 ll II 1 ILm Hi url cutlg Imth m Kalc Hi llt39l chug mum HUI In rm mumm Hum ln man mt mll quotrm um um Emir I l l QM u Eur3 I i l I39ucrg Ilnlhlt l m 39 r mulc Hi luI l39urry vmuxitr um l w muln39 Hi lmI It hm umk mtl mun IH hurt milx xml um Taking heal lransier to lhe syslem and work done by lhe syslem lo be positive quanlilies lhe energy balance relalion is g7 n zanyW ii 7 i J 7 Elm i 7 ii i DI HS Q 7 w HIM 7 Hm kJkmul l39ucl whcrc Hm 2 NAquot 1 i 1 LJLmol ma Hm ENlIH it i ii kJkmnl l39ucl If lhe enlhalpy oi combuslion for a particular reaclion is available g 7 n Ir 2AM 7 it 172Mh 7 i 1 ml lxmnl 39 d quot 39 inleraclions Also combuslion chamber normally involves heal oulpul bul no heal inpul LL Elm1 7 ii 7 i 7 EMU ii 7 ii lerl mi um mu m um i u Mm mi ii in mi Closed Systems I W Taking heal lransier to lhe syslem and work one by lhe syslem closedsyslem e XP cio inlernal energy of a 7 chemical componenl EH in MS We qu Quill Wm Wuquot Um Urm Ukmul l39uc l emha39PY Ulil r 7PV nfn7n07 f 7i7 7pv Q7 n 2AM i 7i 7 PW 7 2N0 ii 7i 7 PP The Pvlerms are negligible for solids and liquids and can be replaced d lo be positive quanlilies lhe general nergy balance relalion can be res ed for a slalionary chemically reacting sed system as Nl fir771 l7PV Nap75 P0 An expression for lhe izing lhe de nilion of enlhalpy by RMT for gases lhal behave as an ideal gas ADIABATIC FLAME TEMPERATURE In the limiting case of no heat loss to the surroundings Q 0 the temperature of the products reaches a maximum which is called the adiabatic flame or adiabatic combustion temperature H Slince Q 0 and w 0 pm Exti l e I l BAAi l e I r The determination of the adiabatic flame temperature by hand requires the use of an iterative technique Insulation PUB 1 The temperature of a Combustion l Products combustion chamber chamber T becomes maximum when Air j l quotW combustion is complete and i no heat is lost to the I surroundings Q 0 The adiabatic ame temperature of a fuel depends on 1the state of the reactants 2the degree of completion of the reaction 3the amount of air used For a specified fuel at a specified state burned with air at a speci ed state the adiabatic ame temperature attains its maximum value when complete combustion occurs with the theoretical amount of air Heat loss Fuel 39 Incomplete Products combusuon gt Air A Tpl39Od lt Tmax gt 0 Dtssomatlon The maximum temperature encountered in a combustion chamber is lower than the theoretical adiabatic flame temperature
Are you sure you want to buy this material for
You're already Subscribed!
Looks like you've already subscribed to StudySoup, you won't need to purchase another subscription to get this material. To access this material simply click 'View Full Document'