Thermodynamic Analysis Of Steam Ejector Refrigeration Cycle

Transcription

1 Prde Univerity Prde e-pb International Refrigeration and Air Conditioning Conference Scool of Mecanical Engineering 0 erodynaic Analyi Of Stea Ejector Refrigeration Cycle Sengcn Li ianjin Key Laboratory of Refrigeration ecnology, Scool of Mecanical Engineering, ianjin Univerity of Coerce, Cina, People' Repblic of, lic@tjc.ed.cn Cnyan Z ianjin Key Laboratory of Refrigeration ecnology, Scool of Mecanical Engineering, ianjin Univerity of Coerce, Cina, People' Repblic of, zcnyan0@6.co Hailin Li Departent of Mecanical and Aeropace Engineering,Wet Virginia Univerity, ailin.li@ail.wv.ed Follow ti and additional work at: ttp:doc.lib.prde.ediracc Li, Sengcn; Z, Cnyan; and Li, Hailin, "erodynaic Analyi Of Stea Ejector Refrigeration Cycle" 0. International Refrigeration and Air Conditioning Conference. Paper 6. ttp:doc.lib.prde.ediracc6 i docent a been ade available trog Prde e-pb, a ervice of te Prde Univerity Librarie. Pleae contact epb@prde.ed for additional inforation. Coplete proceeding ay be acqired in print and on CD-ROM directly fro te Ray W. Herrick Laboratorie at ttp:engineering.prde.ed HerrickEventorderlit.tl

2 06, Page erodynaic Analyi of Stea Ejector Refrigeration Cycle Sengcn LIU *, Cnyan ZHU,Hailin Li * ianjin Key Laboratory of Refrigeration tecnology, Scool of Mecanical Engineering, ianjin Univerity of Coerce, ianjin 00, Cina Pone: , Fax: , Eail: lic@tjc.ed.cn ianjin Key Laboratory of Refrigeration tecnology, Scool of Mecanical Engineering, ianjin Univerity of Coerce, ianjin 00, Cina Pone: , E-ail:zcnyan0@6.co Departent of Mecanical and Aeropace Engineering, Wet Virginia Univerity, Morgantown 6506, Wet Virginia Pone: 0-9-, Fax: , E-ail: ailin.li@ail.wv.ed ABSRAC Stea ejector are capable of drawing large vole of vapor witin a relatively all pace and at a low cot. In ti tdy, te copreor i replaced by a contant-area ixing ejector to redce te energy conption in refrigeration cycle. e inflence of vario paraeter on te perforance of te yte i obtained by an iterative progra and reaon are analyzed in ti paper. e effect of prere difference, te difference of evaporation prere and priary nozzle otlet prere, on te COP and te exergy lo of every coponent in yte i conidered. Finally te key point to optiize te ejector cycle and te ini exergy lo location to optiize te ejector deign are obtained by teoretical reearc. A better ndertanding for te real indtrial application i provided by ti teoretical analyi on te tea ejector refrigeration yte and a fondation for te ilation and experiental reac i laid.. INRODUCION Stea jet refrigeration yte can operate wit low-grade teral energy c a te indtrial wate eat, olar energy, tea exat or oter low-grade energy eat, wic ake it environent-friendly. Copared wit oter type of yte, Stea jet refrigeration yte a any advantage c a trctral iplicity, ig reliability, eay to aintain, low cot and can be ed wit water wic i te ot arle refrigerant. e developent of te firt tea ejector refrigeration cycle propoed by Marice Leblanc Cnnanond and Apornratana, 00a in 90, de to te poor deign and proceing level at tat tie, i liited by it low coefficient perforance COP. However, te invetigation of ejector refrigeration yte a drawn te reearcer attention again in 90 a it environent-friendly and econoically feaible. Ma et al. 00 carried ot an experiental invetigation of a novel 5kW tea jet refrigerator itable for olar energy application. e relt owed tat wit te increae in boiler teperatre, te coefficient of perforance COP did not alway increaed. e axi coefficient of perforance COP and cooling capacity wa fond at a boiler teperatre of abot 90. erefore, for te given operating paraeter, every ejector refrigeration yte a an opti boiler teperatre, at wic te axi coefficient of perforance COP cold be obtained. Dring te experient, te priary flow wa controlled by a pindle. e iilar conclion wa tated by Cnnanond and Apornratana 00b. e relt owed tat, te cooling capacity and coefficient of 5 t International Refrigeration and Air Conditioning Conference at Prde, Jly -, 0

3 06, Page perforance COP can be raied by te decreae in te boiler prere or te increae in evaporation prere. e ator alo tated tat te aont of econdary flid cked into by te priary flid and te oent of ixed tea doinated te yte perforance. In recent year, Btterwort and Seer 00 ed te ig-prere water, wic i available fro vertical pipeline in deep ine aft, to drive an ejector refrigeration yte and te yte perforance a been iproved. Effect of te area ratio γa between priary nozzle and contant area ection on te yte perforance wa tdied by Oliveira et al. 009 ing CFD. e relt indicated tat an increae in γa caed an increae in entrainent ratio and a decreae in te critical back condener prere, o an optial vale old exit in teory for te given operating condition. In order to conider te ignificance of te priary nozzle geoetrie, Apornratana et al. 0 carried ot CFD analyi of eigt different priary nozzle. e relt deontrated tat te expanion angle in te priary nozzle otlet of te priary flid and te poition in te ixing caber of te ixed flid played an iportant role in te ejector perforance. At preent, experient and ilation on te tea jet refrigeration yte ally be ed to iprove te yte perforance. Many paraeter related to te yte perforance ave been analyzed and iproved for te refrigeration cycle wit particlar configration. In ti paper, an iterative progra on a contant-area ejector refrigeration yte, in wic water wa ed a te refrigerant, wa eployed to optiize te deign of te ejector.. HE EJECOR REFRIGERAION CYCLE A te critical coponent in ejector refrigeration cycle, an ejector i conited of te priary nozzle, te ction caber, te ixing caber and te bonic differ. e ig prere atrated tea prodced in te boiler expand and accelerate trog te priary nozzle; it draw te econdary flid fro te evaporator into te ixing caber. e cobined flid aed to be copletely ixed frter copreed in bonic differ and ten dicarged to te condener. μ i defined a te entrainent ratio of te ejector: μ= A ceatic view of te tea ejector refrigeration yte and a P- diagra are own in Fig.and. Norally, te tea ejector refrigeration yte inclde a boiler, ejector, condener, expanion valve, evaporator and a flid pp Figre : A ceatic view of te tea ejector refrigeration yte Figre : e P- diagra of te tea ejector refrigeration yte e priary flid at prere P at tate enter te priary nozzle, expand and accelerate ientropically to te evaporation prere P 0 at tate. e real tea expanded proce to te evaporation prere P 0 wit a nozzle efficiency n =0., end at tate. e accelerated priary flid ck te econdary flid fro evaporator at prere P 0 correponding to tate into te ction caber. Cobined flid aed to be copletely ixed in 5 t International Refrigeration and Air Conditioning Conference at Prde, Jly -, 0

4 06, Page contant-area ection at tate frter copree to tate in bonic differ. e bonic differ i conidered to ave a differ efficiency of d =0.8 wit te ientropic otlet at tate. en ixed flid i dicarged to te condener and cooled at prere Pk to tate 5. e trea leaving te condener i divided into two flow; one of two flow enter te expanion valve and expand to prere P0 at tate 6. Anoter flow i pped to prere P at tate 8, and ten enter te boiler.. ANALYSIS OF HEOREICAL MODEL o iplify te tea jet refrigeration cycle odel, aption are alo ade a follow: e prere loe of condener, evaporator and te connection pipeline of yte coponent are neglected; In addition to te condener and evaporator, tere i no eat excange between oter part of te yte and te environent; e nozzle efficiency n and differ efficiency d of te ejector are given vale Alexi and Rogdali, 00; e trottling proce i een a ientalpic proce; 5 e bcooling degree and evaporation and condenation teperatre are known; 6 e prere of two flid into te ction caber i te ae and te given vale, and te flid in te ejector i one-dienional oogeneo flow.. Energy Analyi Baed on te above aption, te expanding and accelerating proce of te priary flid in te priary nozzle eet energy conervation, A v n Were A refer to cro-ection area of priary nozzle inlet. e velocity of te econdary flid fro te evaporator can be calclated by te forla: A v 5 Were A i te cro-ection area of te inlet pipe in ction caber wic i connected wit te evaporator. e ixing proce of two flid in te ixing caber atifie oent conervation and energy conervation, P A 6 P0 A A Were A i te priary nozzle otlet cro-ection area and A i cro-ection area of nifor ixing caber. e iterative progra take a conervation of ixing proce a te iterative criterion, A v 8 e flid tate in ejector otlet i obtained trog te overall energy balance: 5 t International Refrigeration and Air Conditioning Conference at Prde, Jly -, 0

5 06, Page 5 t International Refrigeration and Air Conditioning Conference at Prde, Jly -, 0 Were i flid velocity in te ejector otlet, by defalt initial vale, and i obtained by iterative calclation. e differ efficiency in diffion proce i: d 0 Cooling capacity of tea jet refrigeration cycle i given a: 6 0 Q Energy conption of tea jet refrigeration cycle i preented by: 5 W e coefficient of perforance for yte i: W Q COP 0. Exergy Lo Analyi of Individal Coponent e exergy lo of te condener Jiang et al., 00: ] [ I k k e exergy lo of trottle valve: 5 6 I f 5 e exergy lo in te evaporator: ] [ I 6 e exergy lo in te boiler: ] [ I e e exergy lo of priary flid paing trog te priary nozzle: 9 ] [ 8

6 06, Page 5 e exergy lo of ixing proce in ixing caber: [ - ] [ ] 9 e exergy lo in prere expanding proce in te bonic differ: [ ] 0 Were i te abient teperatre and given a 00K; k i te Condening teperatre, K; 0 i te Evaporating teperatre, K; i te Boiler teperatre, K.. e Iterative Calclation Progra According to te above terodynaic analyi, te deigned iterative progra i own in Fig.. Define Perforance Paraeter :, 0, k,, t, dt, μ,η n,η d Calclate Strea Prere: P, P0 0, Pk k Call Argent fro EES and Calclate te Paraeter at tate and Solve te Eqn.- and Calclate te Paraeter at tate and Ae Vale of P Solve te Eqn.6-8 and Calclate:, P,, Ceck Ma Conervation: + - ε No Call Argent fro EES and Calclate te Paraeter at tate,, 5, 6, 8 Ye Solve te Eqn.9-0 and Calclate:Q0, W, Ik, Ie, I0, If,π,π,π Figre : Soltion algorit of te iterative proce. RESULS AND DISCUSSION According to te yte deign condition, in wic te boiler teperatre i K, te condening teperatre i 0K and te evaporating teperatre i K, te ejector wa deigned. e EES Klein S et al.0 wa eployed to olve te iterative progra and oe relt were obtained. 5 t International Refrigeration and Air Conditioning Conference at Prde, Jly -, 0

7 06, Page 6 Figre : COP of ejector refrigeration cycle ver boiler teperatre and evaporating teperatre Figre 5: COP of ejector refrigeration cycle ver boiler teperatre and pereat degree Fig. ow tat increaing te boiler teperatre and decreaing te evaporating teperatre decreae te coefficient of perforance COP and it a been proved by Aed and Candra 0. Wen te boiler teperatre i contant, increaing te evaporating teperatre increae te prere difference between te evaporator and te priary nozzle otlet and terefore te econdary flid paing trog te ixing caber i increaed and caed te entrainent ratio and COP increae. Wen te evaporating teperatre i contant, te increae of boiler teperatre increae te expanion angle in te priary nozzle otlet of te priary flid and te ixing caber i coked, t te econdary flid and te COP i decreaed. A own in Fig.5, COP i decreaed wit te pereat degree increae of te priary flid. e pereat degree increae te tea qality in te priary nozzle otlet and decreae te entrainent ratio and COP. Figre 6: COP of ejector refrigeration cycle ver boiler teperatre and entrainent ratio Figre : COP of ejector refrigeration cycle ver condening teperatre and percooling degree Effect of entrainent ratio and condening prere on te yte COP are own in Fig.6. Wit te ae entrainent ratio, te increae of condening prere cae a coke in ejector Alloce et al., 0 and terefore decreae it perforance. e coke in te ejector will be ore erio wit te growt of entrainent ratio. e entrainent ratio affect te COP very erioly; te relationip between te i ΔCOP Δ otly. 5 t International Refrigeration and Air Conditioning Conference at Prde, Jly -, 0

8 06, Page Fig. ow te inflence of te percooling degree on yte COP for different condening teperatre. It can be een fro te figre tat te lower te condening teperatre, te iger te COP, and te rie of te percooling degree increae te COP Y et al., 0. Figre 8: e exergy loe of different coponent ver prere difference Δp Figre 9: COP of ejector refrigeration cycle and exergy lo ver prere difference Δp Fig.8 and 9 provide a vial interpretation of te inflence of prere difference between te evaporator and te priary nozzle otlet on te COP and te exergy lo. It i clear fro te figre tat te prere difference between te evaporator and te priary nozzle otlet a a great ipact on te COP and te exergy lo, a for te iger prere difference, te iger COP and te lower exergy lo for te ejector refrigeration yte. It can be een fro Fig.8 tat te axi exergy lo occr in te ixing proce of te priary flid and te econdary flid. e entrainent ratio and te econdary flid velocity are increaed wit te increae of te prere difference and te relative velocity between te priary flid and te econdary flid decreaed; terefore te exergy lo in te ixing proce i redced. On te oter and, te increae of te prere difference cae te ejector otlet prere cloe to te condening prere and redce te eat tranfer lo and exergy lo in condener. 5. CONCLUSIONS i paper preent te teoretical calclation and analyi on tea jet refrigeration cycle and draw te following conclion: Bot increaing te teperatre of boiler and te pereat of te priary flid can cae coking witin te ejector, entrainent ratio decreaing, te yte COP decreaing; e increae of te condening prere will redce te yte COP wile te increae of bcooling will increae te COP; e axi exergy lo of yte ainly exit in te ixing caber. e prere difference between evaporator and te priary nozzle otlet a a great effect on exergy lo in te ixing proce. e key point of optiizing te yte i optiizing ejector, iproving te econdary flid velocity into te ction caber, wic can redce te relative velocity of two flid and te exergy lo of ejector. Mot of te energy conption of ti experient cycle i te bolier added eat. Wen te yte i eployed in te teral power plant or oter field in wic te low-grade water tea i generated, te yte COP will be iproved rapidly. NOMENCLAURE A Cro-ection area COP Coefficient of perforance e flid entalpy kjkg 5 t International Refrigeration and Air Conditioning Conference at Prde, Jly -, 0

9 06, Page 8 I e exergy lo kj Ma flow rate kg P Prere kpa Δp Prere difference kpa Q0 Cooling capacity kw e entropy at tate * kjkg k eperatre K e flid velocity at tate * W Energy conption kw γa Area ratio μ Entrainent ratio n Nozzle efficiency Differ efficiency d e exergy lo in te priary nozzle kj e exergy lo of ixing proce kj e exergy lo in te bonic differ kj Sbcript * tate of,,,,,, 5, 6,, 8 REFERENCES Cnnanond K., Apornratana S., 00a, Ejector: application in refrigeration tecnology, Renewable and Stainable Energy Review, no. 8: p Ma X.L., Zang W., Oer S.A., Riffat S.B., 00, Experiental invetigation of a novel tea ejector refrigerator itable for olar energy application, Applied eral Engineering, no. 0: p Cnnanond K., Apornratana S., 00b, An experiental invetigation of a tea ejector refrigerator: te analyi of te prere profile along te ejector, Applied eral Engineering, no. : p. -. Btterwort M.D., Seer.J., 00, Hig-prere water a te driving flid in an ejector refrigeration yte, Applied eral Engineering, no. :p Varga S., Oliveira A.C., Diacon B., 009, Nerical aeent of tea ejector efficiencie ing CFD, Int. J. Refrig., no. : p. 0-. Rangtrakoon N, ongtip. et al., 0, CFD ilation on te effect of priary nozzle geoetrie for a tea ejector in refrigeration cycle, International Jornal of eral Science, no. 6: p. -5. Alexi G.K., Rogdali E.D., 00, A verification tdy of tea-ejector refrigeration odel, Applied eral Engineering, no. : p Deng J.Q., Jiang P.X., L., L W., 00, Particlar caracteritic of trancritical CO refrigeration cycle wit an ejector, Applied eral Engineering, no. : p Klein S, Alvarado F. Engineering eqation olver. Middleton, WI: F-Cart Software; 0. Candra V.V., Aed M.R., 0, Experiental and coptational tdie on a tea jet refrigeration yte wit contant area and variable area ejector, Energy Converion and Manageent, no. 9: p Alloce Y., Boden C., Varga S.,0, A CFD analyi of te flow trctre inide a tea ejector to identify te itable experiental operating condition for a olar-driven refrigeration yte, Int. J. Refrig, ttp:dx.doi.org0.06j.ijrefrig Y W.Y., ian R., Yan S.Y., 0, Nerical ilation on te flow trctre and perforance of te ejector, Jornal of Engineering eropyic, Vol., no. : p ACKNOWNLEDGEMEN e EES oftware preented in ti paper i pported by te profeor Yitai Ma worked in ianjin Univerity. 5 t International Refrigeration and Air Conditioning Conference at Prde, Jly -, 0