1 American Institute of Aeronautics and Astronautics

Transcription

1 Pocdings of AIAA/ASME Tmopysics nd H Tnsf Confnc, S. Louis, MO, Jun 22 H Tnsf fom Singl Nuclion Si Duing Sud Pool Boiling of FC-72 Using n Ay of 1 Micon Hs Fi Dmiy Univsiy of Mylnd Dpmn of Mcnicl Engining Collg Pk, MD 2742 USA Emil: fi@ng.umd.du Jungo Kim* Univsiy of Mylnd Dpmn of Mcnicl Engining Collg Pk, MD 2742 USA Emil: kimj@ng.umd.du ABSTRACT Boiling nsf s bn usd in ml conol of compc dvics sinc discovy of ig nsf cofficins ssocid wi boiling pnomn. T objciv of cun wok is o invsig nd dmin boiling nsf mcnisms in singl nd mulipl bubbl mods wi consn sufc mpu boundy condiion. T nsf d conind in is pp is uniqu bcus i is cquid mny locions simulnously using micoscl y insd of singl poin undn bubbls, wic yilds mo dild picu of nsf pocss. Imgs of gowing bubbls w cpud fom blow nd fom sid using wo ig-spd digil vido cms, llowing bubbl bvio o b cold wi nsf msumns. T d indicd influncd by bubbl dpu ws ppoximly lf dpu dim. Micoly vpoion ws obsvd o conibu significn, bu no dominn, fcion of wll nsf in singl bubbl mod. Micoly vpoion ws insignificn in mulipl bubbl mod, nd nsf occud minly oug nsin conducion/micoconvcion duing liquid wing s bubbl dps sufc. * INTRODUCTION Dspi mny dcds of sudy, sill mny conflicing modls gding mcnisms by wic is nsfd duing boiling. Mny of ly modls w bsd on bubbl giion/mico convcion bing pimy mcnism. Ts modls did no includ ps cng, bu lid on n nlogy wi focd convcion, i.., ol of bubbl is o cng lng nd vlociy scls usd o col d. T vpo-liquid xcng modl poposd by Fos nd Gif [1] ssums bubbls c s micopumps mov quniy of o liquid fom wll qul o misp mximum bubbl * All cospondnc sould b ddssd o is uo. dius, plcing i wi cold liquid fom bulk. T nsf fom singl si is ngy quid o is volum of liquid fom bulk mpu o vg of wll nd bulk mpus. Building on wok of Hn nd Giffi [2], Mikic nd Rosnow [3] dvlopd modl of bubbl nsf ssums bubbl scvngs wy supd ly suounding bubbl ov som of influnc s i dps, llowing cold liquid fom bulk o conc sufc. T supd ly is n nwd duing wiing im (im f bubbl dpu nd bfo nuclion of nw bubbl) by nsin conducion ino smi-infini liquid. Tnsin conducion ino is bulk liquid f bubbl dpu ws ssumd mod of nsf. Coop nd Lloyd [4] nd vn Sln l. [5] poposd modl bsd on vpoion of in micoly foms bwn mispiclly gowing bubbl nd wll duing inilly conolld gow. H nsf oug is micoly ws poposd o b pimy mcnism fo bubbl gow. T polifion of modls nd coninuing conovsy suounding singl bubbl nsf is dic sul of lck of libl d gding locl nsf infomion in viciniy of bubbl. T vs mjoiy of xpimnl wok pfomd o d gding boiling s uilizd singl s w lg compd o individul bubbls, mking i difficul o look dils of boiling pocss. Ts xpimns usully usd singl ing lmn opd consn pow, mking i difficul o obin infomion bou locl mpu viions undn bubbls. O xpimns v uilizd sufcs ld consn mpu vgd ov ni, bu locl flux nd mpu w no msubl nd could vy significnly coss. Yddnpuddi nd Kim [6] nd Kim l. [7] usd 96-lmn mico y wi individul s nominlly 27 mm on sid o obin wll nsf infomion und singl bubbls wo wll 1 Amicn Insiu of Aonuics nd Asonuics

2 sups. In bo css y found bubbl nsf mcnisms w diffn fom widly ccpd viw micoly vpoion is dominn nsf mcnism in sud pool boiling. T suls lso indicd nsin conducion nd/o micoconvcion ws pimy nsf mcnism, consisn wi modl of Mikic nd Rosnow [3]. Howv, of influnc of dping bubbl ws muc smll n modl suggsd, nd mpu of liquid coming ino conc wi wll f bubbl dpu ws muc ig n bulk mpu. Bcus dping bubbl ws bou 38 mm in dim, spil soluion usd in is sudy ws insufficin o dmin of influnc of bubbl. In is pp, w xmin suls obind using 96 lmn y simil o on usd li, bu wi individul s nominlly 1 mm x 1 mm. Wll nsf du o singl bubbls spd by disinc wiing im s wll s mulipl bubbl nucling on f no fom singl si xmind. EXPERIMENTAL APPARATUS H y An y of 96 plinum sisnc lmns dposid on quz wf povidd locl sufc flux nd mpu msumns. A poogp of y is sown in Figu 1. Ec lmn in y ws squ in sp, nominlly.1 mm 2 in, nd consisd of 2 mm wid P lins spcd 2 mm p. Ec d nominl sisnc of 8 kw wi mpu cofficin of sisnc of.125 C -1. T lins supply pow o s oud bwn s nd PGA bod. T dils of consucion of simil y givn in Rul nd Kim [8]. Fdbck conol cicui Ec in y ws kp consn mpu by individul fdbck cicuis simil o os usd in owi nmomy s Figu 2 fo scmic of cicui. Any imblnc in Wson bidg ws snsd by n mplifi, wic povidd noug pow o o bing bidg bck ino blnc. T oupu of cicui ws volg coss. T dissipd by givn could b dicly clculd fom is volg nd sisnc. T mpu ws conolld by digil poniom plcd in lg of Wson bidg. Sixn of s cicuis w consucd on singl cd. Six of s cds pluggd ino mobod oud signls fom os compu o individul fdbck cicuis. T d is fd o B l. [9] fo ddiionl dils gding lconics of cicuis. H clibion T y ws clibd in n ovn ld wiin.1 C of s mpu. Clibion consisd of finding digil poniom wip posiion cusd fdbck loop o jus bgin guling fo givn cmb mpu. Ec in y could b vid ov 2 C ng in 4 C incmns. T unciny in mpu is lss n 1 C. D cquisiion sysm T wo d cquisiion cds (PCI-DAS642/16), c cpbl of scnning 64 nlog inpu cnnls mximum spd of 2 khz, w inslld insid Dll OpiPlx GX11 compu. Ec cd smpld oupus of 48 s. T sysm ws usd o obin im-solvd d 374 Hz fom c fo piod of fou sconds. Bo d cquisiion cds w iggd by sm ising dg of TTL signl fom compu. Boiling ig T boiling ig sown in Fig. 3 ws povidd by NASA nd usd in xpimns. T bllows nd suounding ousing llowd s scion pssu o b conolld. A si ws usd o bk up ny sificion wiin s cmb, wil sis of Kpon s cd o ousid of cmb w usd o conol bulk liquid mpu. Hig spd vido T smi-nspn nu of y nbld imgs o b kn fom blow wi igspd digil vido cm (Vision Rsc Pnom IV) s o cqui 256x256 soluion imgs 374 fps. A goup of ig pfomnc wi LEDs ws mound ov y wiin cmb in od o povid big, diffus bckgound fo boom-viw picus of bubbl. A scond igspd digil vido cm (Vision Rsc Pnom IV) ws usd o cod sid-viw imgs sm spd nd soluion. A logn lmp nx o glss window in boiling cmb povidd noug lig fo sid viw imgs. Rcoding of bo cms ws iniid using sm signl usd o igg d cquisiion sysm, nbling nsf msumns nd vido cods o b md simulnously. D ducion Bcus c d is own fdbck conol cicui, w w bl o msu insnnous pow quid o minin c consn 2 Amicn Insiu of Aonuics nd Asonuics

3 mpu. Som of pow supplid o s, owv, is conducd fom lmns o suounding subs nd cn vnully b los by nul convcion o bulk liquid. In is sudy, w insd in nsf inducd only by bubbl cion. T nsf xcusions ound slowly vying bslin w considd nd ssumd o b consqunc of bubbl fomion nd dpu. T bslin of nsf cuv xibid low fquncy oscillion, wic is likly du o nul convcion flow ov divn by mpu diffnc bwn bulk liquid nd y. To obin ffc of bubbl only, six dg polynomil ws fid o slcd poins on bslin nd subcd fom ol im-solvd c fo c in y. T suling nsf cuv could xibi bo posiiv nd ngiv vlus. Ngiv vlus of nsf could sul if liquid dyou duing bubbl gow bov occud, suling in low nsf n would v occud in cs of nul convcion in bsnc of bubbl. An xmpl of d ducion is sown on Fig. 4, in wic ol nsfd fom y is obind by summing nsfd fom c og nd plod on upp cuv. Excusions in nsf bov slowly vying bslin obsvd. Ts xcusions cospond o singl o mulipl bubbl gow squnc fom singl nuclion si on sufc, nd c ws ssignd numb s indicd in Fig. 4. T bslin obind by cuv fi is ovlid on is cuv. T low cuv ws obind by subcing bslin fom ol nsf cuv nd is n cng in nsf du o psnc of bubbl on sufc. RESULTS D w obind und sligly subcoold pool boiling condiions using FC-72 1 m (T s =56.7 C). T sufc mpu of y nd bulk fluid mpu duing xpimn w 76 C nd 52 C, spcivly. I ws obsvd bubbls nucld psisnly fom singl si on y. Bubbls nucld is si lnd bwn wo mods: singl bubbl mod nd mulipl bubbl mod. In singl bubbl mod, disc bubbls dpd fom y wi wiing im bwn dpu of on bubbl nd nuclion of following bubbl. In mulipl bubbl mod, bubbl nuclion ws obsvd immdily f pvious bubbl dpd. T dping bubbl pulld gowing bubbl off sufc pmuly nd bubbls mgd viclly foming smll vpo columns. Evns 1, 12, nd 13 on Figu 4 w mulipl bubbl mods, wi mind bing singl bubbl mods. Evns 1, 12, nd 13 w composd o wo,, nd nuclion vns, spcivly. Singl bubbl Mod Tim solvd imgs of singl bubbl vn 1 kn fom blow sown on Fig. 5. Ec in y s bn colod ccoding o nsf. Sid viw imgs sown on Fig. 6. Nuclion occud bwn ms.27 ms. Bsd on boom viw imgs, bubbl gw o nly full siz by 1.89 ms f nuclion. T bubbl sp smd o b ppoximly mispicl. A lg incs in nsf und lmos ni bubbl ws obsvd duing is im, consisn wi vpoion fom micoly bwn bubbl nd wll. Sing fom 2.16 ms, dvlopmn of low nsf gion cn of bubbl is obsvd, indicing pogssiv dyou of micoly. T dy spo siz, s vidncd by inn cicl, cs mximum ound 3.51 ms. T bubbl bgn o dp sufc is im, nd dy spo sinks s bubbl ncks down. Hig nsf is obsvd on cn s s y wd by bulk liquid. Bubbl dpu occud 5.13 ms, nd is ssocid wi spik in nsf cn s dcys wi im. Evluion of supd liquid modl A plo of im vying pysicl bubbl dim ws obind by fiing cicul mpl o bubbls sown on Fig. 5. T wll nsf d sown in Fig. 4. cn b usd o compu n quivln bubbl dim (d q ) by ssuming ll nsfd fom ll of s gos ino ln : 3 pd q ( ) = Ú v fg q& ( ) A d 6 \ d 6 ( ) = 3 Ú q q& p v fg ( ) A d Assuming im = o b s of nuclion fo singl bubbl, quivln dim is plod long wi pysicl dim on Fig. 7. T slig dcs in msud pysicl dim f bou.8 ms is du o disoion of bubbl gomy duing gow im. I is sn d q is significnly low n msud bubbl dim duing bubbl gow im, implying nsfd fom wll cnno ccoun fo bubbl gow lon. Tis indics bubbl mus v gind g mjoiy of is ngy fom supd liquid ly suounding bubbl. Tis conclusion is consisn wi suls of sudy pfomd by Kim l. [7]. 3 Amicn Insiu of Aonuics nd Asonuics

4 Evluion of nsin conducion modl Mikic nd Rosnow [3] ssumd bubbl scvngd wy supd ly ov n coving wic bubbl dpu dim ( io AR=4.). Ty lso ssumd mpu of liquid coming ino conc wi wll ws bulk liquid mpu. As obsvd in coloizd boom-viw imgs (Fig. 5), of influnc f bubbl dpu is conind wiin ppoximly lf of bubbl dpu dim (A Rio AR=.25). Plos of nsin conducion cuv ssuming vious wll-o-liquid mpu diffncs (DT) nd AR compd o cul nsf viion in Fig. 8. Assuming wing liquid is bulk liquid mpu, nsin conducion cuv is bs fi o msud c wn AR=.1 s sn in Fig. 8. Howv, wing liquid mpu is unknown. Fom psn d, on cn clly s DT sould b smll sinc s wiin of influnc would b subjcd o wing of cold liquid fom bulk duing sinkg of bs dim unil dpu. Tis llows liquid suounding bubbl bs o b pd gdully in dvnc In sudy conducd by Kim l. [7], i ws pdicd AR=.4, wic is consisn wi psn d nd imgs. W cn conclud fom ig spil soluion undn bubbl nd b im-solvd d mpu of wing liquid is ig n of bulk. Howv, i sill nds o b sudid numiclly o mk quniiv conclusion. Mulipl bubbl mod Mulipl bubbl mod is dfind s n vn consiss of ls wo bubbls nucl nd dp wiou ny wiing im in bwn. In is pp, w will xmin only d w codd duing mulipl bubbl vn 13. Sid viw imgs of is pocss sown on Fig. 9. T mulipl bubbl mod ss wi fis bubbl nucling bwn -.27 ms. Tis bubbl dps fom sufc 5.4 ms. A scond bubbl is obsvd o immdily nucl in wk of fis bubbl. Af gow piod, scond bubbl is pulld off sufc pmuly by influnc of fis bubbl ising in liquid. T iniil spicl bubbl sp is disod und influnc of fis-dpd bubbl nd vicl mging wi i. Dpu of scond bubbl occus 1.26 ms nd is immdily followd by nuclion of id bubbl. Tis bubbl gows on sufc nd dpu occus ms -no immdi nuclion is obsvd f id bubbl dps. T nsf disibuion wll supimposd on ig-spd imgs sown on Fig. 1. T nsf disibuion fo fis bubbl is sn o b vy simil o obsvd fo singl bubbl vn. A lg nsf is obsvd jus f bubbl nuclion du o micoly vpoion. T dy spo cn of bubbl gows s micoly dis ou, n sinks s bubbl dps 5.4 ms. T lg nsf cn of y bubbl dpu suggss ni sufc is wd wi liquid, i.., dping bubbl dos no lv vpo ly coving s. T nsf f dpu of fis bubbl dcys wi im vn s scond bubbl gows (5.4 ms o 7.83 ms), nd my b ssocid wi gow of no dy spo on sufc. Bubbl gow duing is im my b du o vpoion -ps conc lin, o fom supd liquid ly. Micoly vpoion is no obsvd, indicing muc of ngy conind wiin supd liquid ly ws dpld duing gow of fis bubbl. T sid viw imgs (Fig. 9) indic mging of scond bubbl wi fis bubbl occus bwn 7.83 ms nd 1.26 ms. T nsf disibuion duing is im indics ig nsf long cicumfnc of bubbl s i is pulld off sufc, wic is consisn wi wing of sufc wi liquid. T mjoiy of nsf duing gow nd dpu of scond bubbl sms o occu duing wing pocss bfo bubbl dpu by nsin conducion nd/o micoconvcion. H nsf disibuions fo id bubbl s i gows nd dps sufc vy simil o os fo scond bubbl, bu id bubbl is no pmuly pulld off sufc by mg wi pvious bubbls. Tim-vying pysicl nd quivln dims plod long wi ol nsf fo vn 13 on Fig. 11. T fis nuclion is followd by pid bubbl gow. T cosponding pid incs in nsf is likly du o micoly vpoion. As in singl nuclion vn, owv, quivln dim indics wll nsf cnno ccoun fo lg bubbl siz. T nuclion of scond bubbl is no ccompnid by n incs in nsf, nd bubbl gow is sn o b muc slow n fo fis bubbl. T quivln dim gin indics bubbl gins ngy fom supd liquid ly duing bubbl gow. T nsf coninus o dcs f nuclion unil scond bubbl bgins o mg wi fis bubbl 7.83 ms. T nsf incss duing is mging pocss nd pks wn scond bubbl dps sufc. Nuclion of id bubbl is ccompnid by dcs in nsf s wll. T nsf iss gin s bubbl bgins o pull off sufc 15 ms. T pk in nsf gin cosponds o bubbl dpu. Simil obsvions w md fo vns 1 nd Amicn Insiu of Aonuics nd Asonuics

5 CONCLUSIONS Spc nd im solvd nsf viions du o bubbl civiy on 96 lmn y consising of 1 mm s w visulizd by using ig spd digil vido cm o obin imgs of bubbl gow nd dpu, n coloizing c in y ccoding insnnous nsf. T cun sudy indics of influnc of bubbl is muc smll n pojcd bubbl dpu, wic vlids pdicd io in sudy conducd by Kim l. [7]. T xminion of clculd quivln dim wi msud pysicl dim duing singl bubbl mod suppos id bubbl gins ngy fom wll s wll s fom supd ly dvlops duing wiing im. Micoly vpoion ws obsvd o conibu significn, bu no dominn, fcion of wll nsf in is mod. Exminion of wll nsf duing mulipl bubbl mods indicd micoly vpoion is insignificn f fis bubbl, nd nsf occus minly oug nsin conducion nd/o micoconvcion duing liquid wing s bubbl dps sufc. ACKNOWLEDGEMENTS T funding fo is wok ws povidd by NASA MSAD und Gn No. NCC3-783, nd is gfully cknowldgd. T gn monio is Jon McQuilln. A d DT fg q T NOMENCLATURE A Dim Wll-o-liquid mpu diffnc Ln Engy Tmpu Tim REFERENCES [1] Fos, K.E., nd Gif, R., 1959, H Tnsf o Boiling Liquid-Mcnism nd Colions, Jounl of H Tnsf, 81, pp [2] Hn, C.Y., nd Giffi, P.,1965, T Mcnism of H Tnsf in Nucl Pool Boiling - P II, Innionl Jounl of H nd Mss Tnsf, 8, pp [3] Mikic, B.B., nd Rosnow, W.M., 1969, A Nw Colion of Pool-Boiling D Including Effc of Hing Sufc Ccisics, Jounl of H Tnsf, 91, pp [4] Coop, M.G., nd Lloyd, A.J.P., 1969, T micoly in nucl pool boiling, Innionl Jounl of H nd Mss Tnsf, 12, pp [5] Vn Sln, S.J.D., Sol, M.S., Col, R., nd Sluy, W.M., 1975, Bubbl gow s in pu nd biny sysms: Combind ffc of lxion nd vpoion micolys, Innionl Jounl of H nd Mss Tnsf, 18, pp [6] Yddnpudi, N., nd Kim, J., 2, Singl Bubbl H Tnsf of Sud Pool Boiling of FC-72, Pocdings of Boiling 2 Engining Foundion Confnc, Ancog, AK. [7] Kim, J., Dmiy, F., nd Yddnpudi, N., Sud Pool Boiling Mcnisms Duing Singl Bubbl H Tnsf: Compison Two Wll Sups, Pocding of 2 IMECE Confnc, Olndo, FL. [8] Rul, T.D., nd Kim, J., 1999, H Tnsf Bvio on Smll Hoizonl Hs Duing Pool Boiling of FC-72, Jounl of H Tnsf, 121, No. 2, pp [9] B, S.W., Kim, J., Mulln, J.D., nd Kim, M.H., 1999, Pliminy Wll H Tnsf Msumns nd Visulizion of bubbl Gow nd Dpu: Sud Nucl Boiling of FC-72, Pocdings of 5 ASME/JSME Join Tml Engining Confnc, Sn Digo, CA. Gk Dnsiy Subscips q Equivln H s Suion v Vpo Supscips. P uni im '' P uni 5 Amicn Insiu of Aonuics nd Asonuics

6 Figu 1: Poogp of y wi singl bubbl nucling on sufc. Figu 2: A scmic digm of fdbck conol cicui. 6 Amicn Insiu of Aonuics nd Asonuics

7 Pssu gulo Compssd i P Sinlss sl bllows. P Viwpos No o scl Lig Si T P LED Fil Fill po/vcuum Window FC-72 Window Micoscl y Mio Hig-spd digil vido Figu 3: Scmic of xpimnl ppus. f s n l o T bslin bslin ducd ol nsf ol nsf im [s] Figu 4: Tol nsf vs. im. 7 Amicn Insiu of Aonuics nd Asonuics

8 Nuclion Dpu Figu 5: Coloizd boom-viw imgs. T non-funcionl s nod in gy. Figu 6: Sid-viw imgs of bubbl gow. T numbs pind blow imgs indic im in millisconds. 8 Amicn Insiu of Aonuics nd Asonuics.2 W

9 [ m i d l b b u B ] W [ f s n im [ms] Figu 7: Pysicl nd quivln bubbl dim vs. im. Bubbl 1 - Equivln Bubbl 2 Bubbl 3 Bubbl 4 Bubbl 5 Bubbl 6 Bubbl 7 Bubbl 8 Bubbl 1 - Pysicl Bubbl 2 Bubbl 3 Bubbl 4 Bubbl 5 Bubbl 6 Bubbl 7 Bubbl 8 DT = 24 K nd AR =.4 DT = 24 K nd AR =.3 DT = 24 K nd AR =.25 DT = 24 K nd AR =.2 DT = 24 K nd AR =.1 DT = 5 K nd AR =.4 DT = 5 K nd AR =.25 Bubbl 3, msud nsf l o T.5 bubbl dpu im [ms] Figu 8: Wll nsf compd wi nsin conducion modl. 9 Amicn Insiu of Aonuics nd Asonuics

10 Figu 9: Sid-viw imgs of mulipl bubbl vn 13. T numbs pind blow imgs indic im in millisconds. T im invl bwn succding fms is.27 ms. T blck-undlind imgs in imlin sow bubbl nuclion nd ls d-undlind img indics finl bubbl dpu. 1 Amicn Insiu of Aonuics nd Asonuics

11 .2 W Figu 1: Coloizd boom-viw imgs of mulipl bubbl vn 13. Non-funcionl s nod in gy. T blck-undlind imgs in imlin sow bubbl nuclion nd d-undlind img indics finl bubbl dpu. 11 Amicn Insiu of Aonuics nd Asonuics

12 [ m i d l b b u B dpu dpu Bubbl 13 - pysicl Bubbl 13 - quivln ol nsf dpu f s n l o im [ms] Figu 11: Pysicl nd quivln dims of mulipl bubbl vn 13 long wi ol nsf c. 12 Amicn Insiu of Aonuics nd Asonuics