Mahdi Deymi-Dashtebayaz. Mahmood Farzaneh Gord. Hamid Reza Rahbari. Introduction 1

Transcription

1 tudying Transmission of Ful torag Bank to NGV ylindr in NG Fast Filling tation Mahdi Dymi-Dashtbayaz hahrood Univrsity of Tchnology Faculty of Mchanical Enginring hahrood, Iran Mahmood Farzanh Gord hahrood Univrsity of Tchnology Faculty of Mchanical Enginring hahrood, Iran Hamid Rza Rahbari hahrood Univrsity of Tchnology Faculty of Mchanical Enginring hahrood, Iran tudying Transmission of Ful torag Bank to NGV ylindr in NG Fast Filling tation Th xact modling of th fast-fill rocss of omrssd Natural Gas (NG fuld storag bank occurring to omrssd Natural Gas Vhicl (NGV cylindrs is an unintlligibl rocss, and should b thoroughly studid. In this ar, a thortical modl basd on mass balanc and thrmodynamic laws has bn dvlod to study dynamic fast filling rocss of NG storag bank to vhicl s (NGV cylindr. Bcaus Mthan occuis a larg rcntag (btwn 70% to 99% of natural gas, for th sak of simlicity it is assumd that Mthan is th only substanc in Natural gas and thrmodynamic rortis tabl has bn mloyd for cas of ral gas modl basd on mthan. For modling th hat transfr, th systm has bn tratd as an adiabatic lum on. Th rsult shows th initial rssur of storag bank has a big ffct on th storag bank volum for bringing u th NGV cylindr to its targt rssur (0 MPa. Th storag bank volums rquird for bringing u th NGV cylindr to its final (targt rssur (0 MPa for various initial storag bank rssur, lik 0.8 MPa (RP = 1.04, 3 MPa (RP = 1.15 and 5 MPa (RP = 1.5 ar rsctivly, 6 and 4 tims th NGV cylindr volum. It is notd that RP is th ratio of storag bank rssur (P to targt rssur (PT (In this rsarch is 0 MPa. Th rsults also showd that ambint tmratur has a big ffct on rfuling rocss, chifly on final NGV cylindr and storag bank conditions. Kywords: comrssd natural gas, NGV cylindr, storag bank, fast filling rocss, thrmodynamic analysis, ntroy gnration Introduction 1 Natural gas is an attractiv ful for vhicls bcaus it is a rlativly clan-burning ful comard with gasolin (Egúsquiza t al., 009. Natural gas as ful is usd in diffrnt vhicls that includ: assngr cars, havy-duty trucks, garbag trucks and buss. Escially for urban vhicls, natural gas is an nvironmntally frindly ful (Tilagon t al., 006. Us of natural gas vhicls (NGVs bgan in Italy in mid In articular, aftr th nrgy crisis in 1970, th NGVs wr raidly dvlod by th govrnmnts of dvlod countris. In Iran th numbrs of NGVs and NG stations hav bn stimatd to b around.6 million vhicls and 1700 fast rfuling stations at th nd of 010 and ar growing raidly (NIOP wbsit. Th natural gas vhicls (NGV usually rciv natural gas from high rssur storag bank at th rfuling stations during filling. Th NGV cylindrs ncountrd a ris in in-cylindr tmratur during th filling du to comlx comrssion and mixing rocsss. This tmratur ris rducs th dnsity of th gas in th cylindr, rsulting in an undr-filld cylindr, rlativ to its ratd scification. If this tmratur ris is not comnsatd for in th fulling station disnsr, by transintly ovr-rssurizing th cylindr, th vhicl usr will xrinc a rducd driving rang. Th caacity of NGV cylindr is a critical subjct to th wid outsrad markting of ths altrnat fulld vhicls. NG is disnsd to a NGV through a rocss known as th fast fill rocss, sinc it is comltd in lss than fiv minuts. Undrfilling of NGV cylindrs could bfall at th fulling stations, at ambint tmraturs gratr than 30. Th rsulting rducd driving rang of th vhicl is an imortant drawback which th gas industry is trying to dominat, without rsorting to unncssarily high fulling station rssurs, or by alying xtnsiv ovrrssurization of th NGV cylindr during th fulling oration. Undrchargd storag cylindrs ar a rsult of th lvatd tmratur which occurs in th NGV cylindr, du to comrssion and othr rocsss. Th NGV industry has mad xcllnt advancmnts in th industry to rovid a systm to rful a NGV comarabl to that of Par rcivd 4 Novmbr 011. Par acctd 17 Fbruary 01 Tchnical Editor: Luís Frnando ilva a gasolin disnsr. Th roblm with th long rfuling tim has bn rmdid, for th most art, to b comarabl to th fill tim (< 5 min takn to fill a gasolin owrd automobil. This fill tim can b rfrrd to as a fast fill or raid charg. Thr hav bn limitd rsarchs in th fild of filling rocss modling in litraturs. In th first rsarchs Kountz (1997 modld fast rfuling rocss of a NGV cylindr basd on first law of thrmodynamics. H dvlod a comutr rogram to modl fast rfuling rocss for a singl rsrvoir. Kountz t al. (1998a, 1998b, 1998c hav also dvlod a NG disnsr control rogram that nsurs intgrat rfuling of NGV cylindrs undr a fast fill scnario. Th rsarchrs ar also undr way to modl fast filling of hydrogn-basd fulling infrastructur, including rsarchs of Liss and Richards (00, Liss t al. (003 and Nwhous and Liss (1999, who hav studid fast filling of th hydrogn cylindr xrimntally. Thy hav rortd a high tmratur incras in th cylindr nding th rocss. A fw rsarchs basd on xrimntal studis wr also carrid out to study fast filling of th NGV cylindr, including work of Thomas and Goulding (00 and hily (003. H drivd that ambint tmratur variation can hav an ffct on th NG fast fill rocss. H also concludd that th tst cylindr was undrfilld vry tim it was raidly rchargd. Farzanh-Gord t al. (007 and Farzanh-Gord (008a hav also modld fast filling rocss. Thy dvlod a comutr rogram basd on th Png-Robinson stat quation and mthan rortis tabl for singl rsrvoir. Thy studid ffcts of ambint tmratur and initial cylindr rssur on final cylindr conditions. In anothr study, Farzanh-Gord t al. (008b rsntd thrmodynamics analysis of cascad storag bank rfuling rocss of NGV cylindrs. Th rsults of this rsarch indicatd that ambint tmratur has a big ffct on filling rocss and final NGV cylindr conditions. Farzanh-Gord t al. (011 hav mloyd a thortical analysis to study ffcts of buffr and cascad storag banks on rformanc of a NG fulling station. It is found that th filling tim rquird for bringing u th NGV onboard cylindr to its final rssur in th buffr storag systm is about 66% lss than th cascad storag bank. Th chargd mass for cascad bank is about 80% of th buffr bank which givs an advantag to buffr bank J. of th Braz. oc. of Mch. ci. & Eng. oyright 01 by ABM Octobr-Dcmbr 01, Vol. XXXIV, No. 4 / 49

2 Dymi-Dashtbayaz t al. ovr cascad on. Th biggst advantag of th cascad bank ovr th buffr is 50% lss ntroy gnration for this configuration, which robably causs much lowr rquird comrssor inut work for this configuration comaring to buffr bank. Farzanh-Gord t al. (01a, 01b hav also studid ffcts of natural gas comositions on fast filling rocss for buffr and cascad storag banks. In ths rsarchs, th conditions of storag banks wr considrd constant. Entroy is an imortant aramtr of thrmodynamic rortis (Moisés t al., 010. Th scond law has bn mloyd in this study to calculat th amount of ntroy gnration thortically. Entroy gnration is associatd with thrmodynamic irrvrsibility, which is common in all tys of thrmal systms. Various sourcs ar accountabl for th ntroy gnration. Thr hav bn numrous rsarchs in th fild of ntroy gnration. Bjan (198, 1996 has concntratd uon th diffrnt mchanisms rsonsibl for ntroy gnration in alid thrmal nginring. Gnration of ntroy dstroys th availabl work of a systm. Thrfor, it maks good nginring sns to focus on irrvrsibility (Bjan, 197 of hat transfr and fluid flow rocsss and try to undrstand th function of rlatd ntroy gnration mchanisms. inc thn, a lot of invstigations hav bn carrid out to comut th ntroy gnration and irrvrsibility rofils for diffrnt gomtric configurations, flow situations, and thrmal boundary conditions. Hr, Entroy gnration minimization has bn mloyd as a tool to dtrmin th amount of work dstruction during filling rocss. In this ar th goal is to study th ffcts of changing dynamic storag bank conditions on NGV cylindr filling tim from a rssurizd natural gas rsrvoir. A thortical modl basd on mass balanc and thrmodynamic laws is rsntd. In this rsarch, firstly, will b studid th ffct of initial storag bank rssur on th volum that ndd for bringing u th NGV cylindr to its Targt rssur (0 MPa. Also th aim is to dtrmin mass flows, thrmodynamic rortis and ntroy gnration in th cylindr and storag bank at any tim during th filling rocss. In addition, th ffcts of ambint (initial tmratur on imortant aramtrs influncing filling rocss ar studid. Nomnclatur A = ara, m d = orific discharg cofficint, dimnsionlss, = constant rssur and volum scific hats, kj/(kg K g = gravitational acclration, m/s h = scific nthaly, kj/kg = mass flow rat, kg/s M = molcular wight, kg/kmol P = rssur, (bar or Pa = hat transfr rat, kw T = tmratur, (K or o u = intrnal nrgy, kj/kg h = nthaly, kj/kg s = ntroy, kj/ K t = tim, s V = volum, m 3 W = actual work, kj/kg = actual work rat, (kw or MW z = hight, m Z = comrssibility factor, dimnsionlss RP = ratio of rssur, dimnsionlss RV = ratio of volum, dimnsionlss Grk ymbols v = scific volum, m 3 /kg = isntroic xonnt, dimnsionlss = air dnsity, kg/m 3 ubscrits = NGV cylindr V = control volum = storag bank i = initial or inlt condition = xit condition = rsnt condition s = start of filling rocss a, = ambint av = avrag gn = gnration tot = total Natural Gas Rfuling tation Figur 1 shows a tyical NG filling station. Natural gas from th distribution ilin, usually low rssur at < 0.4 MPa or ossibly mdium rssur (1.6 MPa, is comrssd using a larg multi-stag comrssor into a storag bank. This systm is maintaind at a rssur highr than that in th vhicl s on-board storag so that gas flows to th vhicl undr diffrntial rssurs. Tyically, th storag bank will orat in th rang of 0.5 MPa to 5 MPa, whil th vhicl s maximum on-board cylindr rssur is 0 MPa. Figur 1. A schmatic diagram of NGV rfuling station. Dfinition of Dimnsionlss Paramtrs Thr ar a fw imortant aramtrs affcting th filling rocss which should firstly b introducd. In NGV filling rocss, thrmodynamic rortis in storag bank lay imortant rol on filling rocss. Two main thrmodynamics in rortis storag bank ar rssur and tmratur. As shown in Fig., storag bank has its own tmratur (T and rssur (P which assumd changd whil th rssur and tmratur within NGV cylindr varis during filling rocss. Tyically, th rssur in storag bank (P is in rang of 0.5 MPa to 5 MPa, whil th vhicl s maximum NGV cylindr rssur is 0 MPa. In othr words, th targt rssur (PT in th fulling rocss is 0 MPa. To maintain th final rssur within NGV cylindr high nough, th rssur (P within storag bank in initial filling rocss could b assumd btwn 0.8 MPa to 5 MPa. Th first and scond dimnsionlss numbrs introducd in this study ar RPc and RPs that rsctivly ar th ratio of NGV cylindr rssur (P and storag bank rssur (P to targt rssur (PT (In this rsarch is 0 MPa, which ar dfind as follows: 430 / Vol. XXXIV, No. 4, Octobr-Dcmbr 01 ABM

3 tudying Transmission of Ful torag Bank to NGV ylindr in NG Fast Filling tation RP = P / P (1 T RP = P / P ( T P P ( γ + 1 if γ 1 γ (6 It should b notd that at th nd of NGV filling rocss, th numbr should rach 1, which mans that th final rssur of NGV cylindr should b qual to targt rssur. Th nxt dimnsionlss numbr introducd in this sction is RV, which is th ratio of storag bank volum (V to NGV cylindr volum (V and dfind as follows: RV = V / V (3 Not that th conditions of storag bank during filling rocss ar changing, finding th ratio of volum storag bank rathr than volum of cylindr to achiv th targt conditions of rfuling will b ncssary. Thrmodynamic Modl Balanc nrgy modl To modl th fast filling rocss and dvlo a mathmatical mthod, th NGV cylindr or storag bank is considrd as a thrmodynamics on systm that gos through a quasi-stady rocss. = γ P ρ A d o r ific γ + 1 γ if P γ 1 > ( P + 1 γ γ + 1 ( γ 1 In Eqs. (6 and (7 is discharg cofficint of th orific. Th first laws of thrmodynamics for a control volum in gnral form can b writtn as follows: Q& cv + i( hi + Vi /+ gzi = d / [ m( u + V /+ gz] cv + W& cv ( h + V /+ gz + Th work trm is zro in th filling rocss and th chang in otntial and kintic nrgy can b nglctd. Th quation thn could b simlifid for NGV cylindr and storag bank as blow: (7 (8 du du Vi = δq& + i( + hi For NGV ylindr V = δq& ( + h For torag Bank (9 T Figur. A schmatic figur of thrmodynamic systm. To dvlo a thortical modl, th consrvation of mass and first law of thrmodynamics hav bn alid to th control volum (storag bank or NGV cylindr, to find thrmodynamics rortis. onsidring th NGV cylindr or storag bank as a control volum, th consrvation of mass (continuity quation may b writtn as follow: dm dm = = i For N G V ylindr For torag Bank In quation (4, is th inlt mass flow rat in NGV cylindr and is th outlt mass flow rat of storag bank. It is imortant that th inlt mass flow rat of NGV cylindr,, is qual to th outlt mass flow rat of storag bank,, as follows: = = (5 Th valu of can b obtaind by considring an isntroic xansion through an orific. Alying gas dynamics laws: P γ P P = ρ A ( ( ( 1 ( d orific P γ 1 ρ P 1 γ 1 γ γ 1 (4 Vi V As h = + hi = + h and = =, th abov quation could furthr b simlifid as: du V = δq& ± h (10 V In Eq. (10, th ositiv and ngativ signs hav bn usd rsctivly for NGV cylindr and storag bank. Th hat lost from th NGV cylindr and storag bank to nvironmnt could b calculatd as V HV V V ( δq& = U A T T (11 U, A, T and ar rsctivly th ovrall hat transfr cofficint, surfac ara, in-cylindr tmratur and ambint tmratur, for control volum that could b NGV cylindr or storag bank. By combining Eqs. (4, (10 and (11, th following quation is obtaind: d( mu V dm = U ( V V AV TV T ± h (1 Or in th following form: d( mv uv d( mv h m = U V AV ( TV T (13 Th abov quation could b rarrangd in th following form: J. of th Braz. oc. of Mch. ci. & Eng. oyright 01 by ABM Octobr-Dcmbr 01, Vol. XXXIV, No. 4 / 431

4 Dymi-Dashtbayaz t al. ( d( m u m m h = U A T T (14 V V V V V V Th abov quation could b intgratd from outst of filling, u to rsnt tim as: o t ( d( m u m m h = U A T T (15 V V V R V V V o Th intgration of th abov quation for a storag bank with singl rsrvoir fulling station rsultd in: m ( u h m ( u h = U A T t m (16 R o o R V V av whn and ar mass of chargd gas at rsnt and outst of filling rocss, is avrag tmratur diffrnc btwn cylindr and nvironmnt which is dfind as: av 1 t ( V (17 t o T = T T Th first law of thrmodynamics for th NGV cylindr or storag bank finally can b writtn as: mo u = h U AV Tavt ± ( uo h (18 m Equations (6, (7 and (18 could b mloyd to obtain th two thrmodynamic rortis of in-cylindr or storag bank natural gas at any tim. For an adiabatic systm, Eq. (18 could b mor simlifid as: mo u = h ± ( uo h (19 m Not that in Eq. (19, th control volum could b usd for th NGV cylindr or storag bank. Also th ositiv and ngativ signs hav bn usd rsctivly for NGV cylindr and storag bank. By knowing two indndnt thrmodynamic rortis (hr scific intrnal nrgy and scific volum, th othr in-cylindr and in-storag bank rortis can b found. Entroy gnration modl Th scond law of thrmodynamic and flow rocsss occurring in th a storag bank of th NG filling station, adotd in this study, maks it ossibl to valuat th ntroy gnration rat, & gn, for th charactristic nods of th systm. Th scond law of thrmodynamics for filling rocss of a NGV cylindr and storag bank could b rsntd as: & = d / δq& / T s 0 For NGV ylindr gn, i i & = d / δq& / T + s 0 For torag Bank gn, (0 Hr, all irrvrsibility is assumd to occur from inlt to incylindr osition. This maks an isntroic xansion from rsrvoir to inlt osition, which mans s i = s = s. = = onsidring this assumtion and this vrity that i and also combining Eqs. (4, (11 and (0, th following quation can b obtaind: d( m s dm & gn, = s + UH A ( T T / T For NGV ylindr (1 d( mr s dm & gn, = + s + UH A ( T T / T For torag Bank Th total ntroy gnration could b obtaind as summation of ntroy gnration of NGV cylindr & gn, and storag bank & gn,, as blow: & = & + & ( tot gn, gn, Th abov quation can b rwrittn as: d( m s d( m s & tot = + UH A ( T T / T + + UH A ( T T / T (3 Equation (3 can b mor simlifid for an adiabatic systm as: d( m s d( m s & tot = + (4 Or in th following form: & = d ( m s m s + d( m s + m s (5 tot Th abov quation can b intgratd from start of filling to th rsnt tim as: = d( m s m s + d( m s + m s tot s s (6 For a fulling station with storag bank, th intgration of th abov quation rsultd in a siml quation as: = m ( s s m ( s s + m ( s s m ( s s (7 tot s s s s Rsults and Discussion In this study, th NGV cylindr and storag bank hav bn considrd adiabatic, as a rsult, th charactristics of th orific will not affct th final tmratur stat in th cylindr. Th orific diamtr and th NGV cylindr volum wr considrd to b 1 mm and 67 littrs rsctivly. Also, for modling th hat transfr it is usd lumd-systm modl, which mans th rsults rsntd in this work ar for adiabatic orating conditions. Bcaus Mthan occuis a larg rcntag (btwn 70% to 99% of natural gas, for th sak of simlicity it is assumd that Mthan is th only substanc in Natural gas and thrmodynamic rortis tabl has bn mloyd for th cas of ral gas modl basd on mthan. Th rsults hav bn rsntd in Fig.. In NG station, whn th filling rocss is comltd th final rssur of th NGV cylindr incrass to 0 MPa. To achiv this goal, dtrmination of th volum of th storag bank is vry 43 / Vol. XXXIV, No. 4, Octobr-Dcmbr 01 ABM

5 tudying Transmission of Ful torag Bank to NGV ylindr in NG Fast Filling tation imortant. Figur 3 shows th final NGV cylindr rssur for th various RV numbrs. As mntiond in rvious sctions th RV numbr is dfind as ratio of storag bank volum to NGV onboard cylindr volum. As shown in this figur, for bringing u th NGV cylindr to its targt rssur (0 MPa or RP qual to 1, th various RV numbrs (ratio volum of storag bank to NGV cylindr should b slctd. For studying th ffct variation of initial rssur storag bank on filling rocss, th RP dimnsionlss numbr was introducd in th rvious sction. In Fig. 3, th initial rssur of storag bank has changd from 0.8 MPa (RP = 1.04 to 5 MPa (RP = 1.5. In othr words, for comlting rfuling rocss, th volum of storag bank should b slctd rsctivly, 6 and 4 tims th NGV cylindr s for diffrnt initial rssurs storag bank as 0.8 MPa (RP = 1.04, 3 MPa (RP = 1.15 and 5 MPa (RP = 1.5. As is clar in this figur, th initial rssur of storag bank has a big ffct on th storag bank volum for bringing u th NGV cylindr to its targt rssur (0 MPa. Bcaus th minimum of initial rssur in storag bank is a critical condition for filling rocss, th rsults hav bn rsntd hr for storag bank with initial rssur 0.8 MPa. Figur 5 shows, for th cas whr initial tmratur was kt constant at 300 K, dynamic NGV in-cylindr and storag bank tmratur rofils. Not from Fig. 5 that th in-cylindr gas tmratur falls nding th arly stags of charging bfor rising to a final valu. Th roof for th di in this curv, in th arly art of th filling of almost mty NGV cylindr is consqunc of th Joul-Thomson cooling ffct, which th gas undrgos in th isnthalic xansion through th orific, from th 0.8 MPa suly rssur to th initially low 0.1 MPa NGV cylindr rssur. This cold gas mixs with and comrsss th gas originally in th NGV cylindr, with th rsult that th combind mixd gas tmratur initially rducs. Whn th comrssion and convrsion of suly nthaly nrgy to NGV cylindr intrnal nrgy ovrcoms th Joul-Thomson cooling ffct, which bcoms lssr as th NGV cylindr rssur incrass, th mixd gas tmratur in th NGV cylindr starts to incras. In othr words, th storag bank tmratur rmains narly constant during filling rocss. Figur 5. Tmratur rofils of NGV cylindr and storag bank during filling rocss. Figur 3. Effct of RV numbr (volum storag bank to NGV cylindr volum and RP numbr (P/PT on RP numbr (P/PT. Figur 4 shows dynamic rssur rofils of NGV cylindr and storag bank during filling rocss. Not from th figur that th tim rquird to rach th final rssur (0 MPa in NGV cylindr is about 90 sconds. Farzanh-Gord t al. (011 hav analyzd th sam rocss but with fixd rsrvoir conditions and obtaind lowr filling tim. This shows that th rsrvoir condition has ffcts on th filling tim. Figur 6 shows mass flow rat rofil that flows from storag bank and ntrs into NGV onboard cylindr during filling rocss whil initial (ambint condition is kt constant at 300 K and 0.1 MPa. According to Fig. 6, in arly art of filling, mass flow rats ar narly constant du to choking. Not from th figur that th mass flow rat which ntrd th NGV cylindr is qual to th mass flow rat that xitd th storag bank. Figur 4. NGV in-cylindr and storag bank rssur rofils during filling rocss. Figur 6. Mass flow rat rofil during th NG filling rocss with initial tmratur of 300 K and 0.1 MPa. J. of th Braz. oc. of Mch. ci. & Eng. oyright 01 by ABM Octobr-Dcmbr 01, Vol. XXXIV, No. 4 / 433

6 Dymi-Dashtbayaz t al. In Fig. 7, th NGV in-cylindr and in-storag bank mass chang rofils during filling rocss ar shown whil initial tmratur and rssur ar kt stady at 300 K and 0.1 MPa. Not from th figur that th mass rquirmnt of NG ful in storag bank for comlting filling rocss is qual to 34 kg and th final incylindr mass incrasd to 8 kg. As rminiscd rviously, ntroy gnration is dndnt on thrmodynamic irrvrsibility. Irrvrsibility dstroys availabl work in th NG filling station. As th availabl work is rovidd by th comrssor, so on could conclud that as ntroy gnration is dcrasd, availabl work dstruction is dcrasd too. Figur 9 shows ntroy gnration in NGV cylindr, storag bank and total ntroy gnration obtaind from summation of ntroy gnration of NGV cylindr and storag bank for filling an mty NGV cylindr. As sn in Fig. 9, th ntroy gnration in storag bank is much furthr than ntroy gnration of NGV cylindr. Entroy Gnration (kj/k Figur 7. NGV in-cylindr and in-storag bank mass variations during filling rocss with initial conditions of 300 K and 0.1 MPa. In th rvious studis (Farzanh-Gord t al., 007 and Farzanh-Gord, 008a, it was found that initials in-cylindr tmratur (which could b rrsntd by ambint tmratur hav big ffcts on th final NGV in-cylindr and storag bank rortis. Figur 8 shows how th chargd mass varis with initial tmratur (in th NGV cylindrs and storag bank which could illustrat th ffct of ambint tmratur. It can b sn as initial tmratur incrass chargd mass dcrass. This mans that driving rang of NG vhicls will dcras if filling carrid out in hot wathr comard to th coldr conditions. Th ambint tmratur has oosit ffcts on final incylindr and storag bank tmraturs and chargd masss. Th final in-cylindr and storag bank tmraturs incras as ambint tmratur incrass whras th final mass of NGV cylindr and storag bank with diminution of ambint tmratur incrass. Th significant oint is that by incrasing initial (ambint tmratur, th final in-cylindr and storag bank tmraturs incras linarly. Figur 9. Entroy gnration in NGV cylindr, storag bank and summation of two. Figur 10 shows th ffct of initial tmratur on th ntroy gnration of NGV cylindr, storag bank and summation of two. As in this figur, for NGV cylindr and storag bank, th ntroy gnration at low tmraturs is much highr than at high tmraturs, so th ntroy gnration in 70 K is, rsctivly, 5.1 kj/kgk and kj/kgk for NGV cylindr and storag bank, whil th ntroy gnration in 340 K is, rsctivly, 3.08 kj/kgk and 3.07 kj/kgk. Figur 10. Effct of initial (ambint tmratur on ntroy gnration in NGV cylindr, storag bank and total summation. Figur 8. Effct of initial (ambint tmratur on final in-cylindr and storag bank tmraturs. onclusion Th first and scond laws of thrmodynamics hav bn usd as thortical tools in ordr to invstigat conditions of NGV cylindr and storag bank nding filling rocss. A thortical analysis has bn built to study th blow downing storag bank and filling NGV cylindr. Th imortant aramtrs that this ar has invstigatd includ variation of tmratur, rssur, mass flow rat, chargd mass and ntroy gnration for NGV cylindr and storag bank. Also, it is discussd ffcts of ambint tmratur on ths aramtrs. As ntroy gnration is associatd with th comrssor 434 / Vol. XXXIV, No. 4, Octobr-Dcmbr 01 ABM

7 tudying Transmission of Ful torag Bank to NGV ylindr in NG Fast Filling tation inut work, it is assumd that, as ntroy gnration rducs, comrssor work dcrass too. Th rsults show that th initial rssur of storag bank has a big ffct on th storag bank volum for bringing u th NGV cylindr to its targt rssur (0 MPa. It is found that th volum storag bank rquird for bringing u th NGV on-board cylindr to its final rssur (0 MPa for th various initial storag bank rssurs, lik 0.8 MPa (RP = 1.04, 3 MPa (RP = 1.15 and 5 MPa (RP = 1.5 ar rsctivly, 6 and 4 tims th volum of NGV cylindr. Th rsults also rval that th ntroy gnration during filling rocss in storag bank is much furthr than ntroy gnration of NGV cylindr. onsidring th abov commnts, on could conclud that th ambint tmratur has big ffcts on filling rocss, final incylindr and storag bank conditions. Rfrncs Bjan, A., 1979, A study of ntroy gnration in fundamntal convctiv hat transfr, J. Hat Transfr, Vol. 101, Bjan, A., 198, cond-law analysis in hat transfr and thrmal dsign, Adv. Hat Transfr, Vol. 15, Bjan, A., 1996, Entroy Gnration Minimization, R, Boca Raton, NY. Egúsquiza, J.., Braga,.L and Braga,.V.M., 009, Prformanc and gasous missions charactristics of a natural gas/disl dual ful turbochargd and aftr coold ngin, J. Braz. oc. Mch. ci. & Eng., Vol. 31, No., Farzanh-Gord, M., Eftkhari, H., Hashmi,., Magrbi, M. and Dorafshan, M., 007, Th ffct of initial conditions on filling rocss of NG cylindrs, Th scond Intrnational confrnc on Modlling, imulation and Alid otimization, Abu Dhabi, UAE, March 4-7. Farzanh-Gord, M., 008a, omrssd natural gas ingl rsrvoir filling rocss, Gas intrnational Enginring and Managmnt, Vol. 48, Issu 6, July/August, Farzanh-Gord, M., Hashmi,.H. and Farzanh-Kord, A., 008b, Thrmodynamics Analysis of ascad Rsrvoirs Filling Procss of Natural Gas Vhicl ylindrs, World Alid cincs Journal, Vol. 5, No., Farzanh-Gord, M., Dymi-Dashtbayaz, M. and Rahbari, H.R., 011, tudying ffcts of storag tys on rformanc of NG filling stations, Journal of Natural Gas cinc and Enginring, Vol. 3, Farzanh-Gord, M., Rahbari, H.R. and Dymi-Dashtbayaz, M., 01a, Effcts of Natural Gas omositions on NG Fast Filling Procss for Buffr torag ystm, ar acctd by Oil and Gas cinc and Tchnology. Farzanh-Gord, M., Dymi-Dashtbayaz, M. and Rahbari, HR., 01b, Otimizing omrssd Natural Gas Filling tations Rsrvoir Prssur Basd on Thrmodynamic Analysis, Int. J. Exrgy, Vol. 10, No. 3, Kountz, K., 1994, Modlling Th Fast Fill Procss in Natural Gas Vhicl torag ylindrs, Amrican hmical ocity Par at 07th National A Mting, March. Kountz, K., Knnth J. and Blazk,.F., 1997, NGV Fulling tation and Disnsr ontrol ystms, Rort GRI-97/0398, Gas Rsarch Institut, hicago, Illinois, Novmbr. Kountz, K., Liss, W. and Blazk,., 1998a, Mthod and Aaratus For Disnsing omrssd Natural Gas, U.. Patnt 5, 75, 55, May 19. Kountz, K., Liss, W. and Blazk,., 1998b, Automatd Procss and ystm For Disnsing omrssd Natural Gas, U.. Patnt 5,810,058, t. Kountz, K., Liss, W. and Blazk,., 1998c, A Nw Natural Gas Disnsr ontrol ystm, Intrnational Gas Rsarch onfrnc, an Digo, Novmbr 3. Liss, W.E. and Richards, M., 00, Dvlomnt of a Natural Gas to Hydrogn Fulling tation, Toical Rort for U.. DOE, GTI-0/0193, t. Liss, W.E., Richards, M.E., Kountz, K. and Kriha, K., 003, Modlling and Tsting of Fast-Fill ontrol Algorithms for Hydrogn Fulling, National Hydrogn Association Mting, March. Marclino Nto, M.A. and Barbosa Jr., J.R., 010, Modlling of stat and thrmodynamic cycl rortis of HFO-134yf using a cubic quation of stat, J. Braz. oc. Mch. ci. & Eng., Vol. 3, National Iran Oil Products Distribution omany (NIOP, wbsit availabl at: Nwhous, N.L. and Liss, W.E., 1999, Fast Filling of NGV Ful ontainrs, AE ar hily, E., 00, tudy of natural gas vhicls (NGV during th fast fills rocss, Thsis for Mastr of cinc, ollg of Enginring and Minral Rsourcs at Wst Virginia Univrsity. Tilagon, R., Vnturi,. and Monnir, G., 006, Natural Gas - an Environmntally Frindly Ful for Urban Vhicls: th mart Dmonstrator Aroach, Oil & Gas cinc and Tchnology Rv. IFP, Vol. 61, No. 1, Thomas, G., Goulding J. and Muntam,., 00, Aroval and Vrification of NG Disnsrs, NWML KT11 Rort. J. of th Braz. oc. of Mch. ci. & Eng. oyright 01 by ABM Octobr-Dcmbr 01, Vol. XXXIV, No. 4 / 435