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1 Kbe Unvesty Repsty : Kenel タイトル Ttle 著者 Auth(s) 掲載誌 巻号 ページ Ctatn 刊行日 Issue date 資源タイプ Resuce Type 版区分 Resuce Vesn 権利 Rghts DOI JaLCDOI URL Tansent ctcal heat fluxes f subcled wate flw blng n a SUS304-ccula tube caused by a apd decease n velcty fm nnblng egme Hata, Kch / Fukuda, Katsuya / Masuzak, Suguu Expemental Themal and Flud Scence,66: Junal Atcle / 学術雑誌論文 auth 015. Ths manuscpt vesn s made avalable unde the CC-BY- NC-ND 4.0 lcense /j.expthemflusc PDF ssue:

2 TRANSIENT CRITICAL HEAT FLUXES OF SUBCOOLED WATER FLOW BOILING IN A SUS304-CIRCULAR TUBE CAUSED BY A RAPID DECREASE IN VELOCITY FROM NON-BOILING REGIME Kch Hata Insttute f Advanced Enegy, Kyt Unv., Gkash, Uj, Kyt , Japan Phne: hata@ae.kyt-u.ac.jp Katsuya Fukuda Dept. f Mane Eng., Kbe Unv., 5-1-1, Fukaemnam, Kbe , Japan Phne: fukuda@matme.kbe-u.ac.jp Suguu Masuzak Natnal Insttute f Fusn Scence, Osh-ch, Tk, Gfu , Japan Phne: masuzak@lhd.nfs.ac.jp ABSTRACT The flw tansent ctcal heat fluxes (FT-CHFs, q c,sub) n a SUS304-ccula tube caused by a apd decease n velcty fm nn-blng egme ae systematcally measued f vaus ntal flw velctes, ntal heat fluxes, nlet lqud tempeatues, utlet pessues and deceleatns caused by a apd decease n velcty by the expemental wate lp cmpsed f a multstage cannedtype cculatn pump cntlled by an nvete. The SUS304-ccula tubes f nne damete (d=6 mm), heated length (L=59.5 mm), L/d (=9.9) and wall thckness (=0.5 mm) wth aveage suface ughness (Ra=3.89 m) ae used n ths wk. The flw tansent CHFs f SUS304-ccula tube ae cmpaed wth auths steady-state CHF data f the empty VERTICAL and HORIZONTAL SUS304-ccula tubes and the values calculated by auths steady-state CHF celatns aganst utlet and nlet subclngs f the empty ccula tube. The nfluences f ntal flw velcty (u 0), ntal heat flux (q 0) and deceleatn caused by a apd decease n velcty () n the flw tansent CHF ae nvestgated nt detals and the wdely and pecsely pedctable celatns f CHF and flw velcty at the flw tansent CHF f the ccula tube s gven based n the expemental data. The celatns can descbe the flw velcty and the CHFs at the flw tansent CHFs f SUS304-ccula tube btaned n ths wk wthn 0 % dffeence. Key Wds: 1

3 Tansent Ctcal Heat Flux, Subcled Wate Flw Blng, SUS304-Ccula Tube, Rapd Decease n Velcty, Deceleatn, Nn- Blng Regme INTRODUCTION Flw tansent ctcal heat fluxes f subcled wate flw blng n a SUS304-ccula tube caused by a apd decease n velcty fm nn-blng egme s necessay t nvestgate the elablty f a dvet n a nuclea fusn faclty at a lss f flw accdent. The nuclea fusn faclty has tw peatn mdes. One s the steady-state peatn mde, and the the s the tansent ne. The plasma facng mateal n tansent peatn mde s expsed t a heat lad thee tmes lage me than dung steadystate peatn f seveal secnds. The knwledge f hgh heat flux heat emval dung vaus deceleatns caused by the apd deceases n velcty (flw tansents) becmes especally vey mptant t take the heat ut f the plasma facng mateal f sht pulse hgh heat flux test mde. The nfluence f deceleatn caused by a apd decease n velcty n tansent CHF n subcled wate flw wll be mmedately suppsed t be appled t themal analyss f the dvet f a helcal type fusn expemental devce whch s Lage Helcal Devce (LHD) lcated n Natnal Insttute f Fusn Scence (NIFS), Japan. Many eseaches have expementally studed the steady state CHFs unfmly heated n the ccula tube wth and wthut twsted-tape nset by a steadly nceasng cuent at a fxed mass velcty f Fusn React Safety (FRS), shwn that the ccula tube wth twsted-tape nset pvde cnsdeable enhancement f CHFs n subcled flw blng and gven the celatns f calculatng CHFs n the ccula tube wth twsted-tape nset [1-9]. We have suppsed that the enhancement f CHFs f the ccula tube wth twsted-tape nset wll be due t eductn f cnductve sub-laye thckness n heated suface f test tube and due t an ncease n lqud flw velcty fm staght flw t swl ne, nt new mechansm f heat tansfe css. And futheme, we have als suppsed that flw velcty wll affect the ncpent blng supeheat and the nucleate blng heat tansfe up t the CHF. Incpent blng supeheat may shft t a vey hgh value at hghe flw velcty and a dect tanstn t flm blng a tend f a decease n CHF wth a delay f blng ntatn may ccu due t the hetegeneus spntaneus nucleatn but nt due t the hyd-dynamc nstablty. The accuate measuement f the subcled blng heat tansfe up t the CHF s necessay t clafy a change n the mechansm f CHF. Recently, we systematcally measued the pwe tansent ctcal heat fluxes (PT-CHFs) f subcled wate flw blng n a SUS304-ccula tube f the nne damete (d=6 mm), the heated length (L=59.4 mm), the effectve length (L eff=49.4 mm), L/d (=9.9), L eff/d (=8.3) and the wall thckness (=0.5 mm) wth the twsted-tape f wdth (w=5.6 mm), thckness ( T=0.6 mm), ttal length (l=37 mm) and twst ats, y [H/d=(ptch f 180 tatn)/d], f.40, 3.37 and 4.45 f the mass velctes (G=3988 t 1360

4 kg/m s), the nlet lqud tempeatues (T n=87.55 t K), the utlet pessues (P ut= t kpa) and the expnentally nceasng heat nputs (Q=Q 0exp(t/), =6.85 ms t 8.43 s). The nfluences f twsted-tape nset, twst at, heatng ate and swl velcty n the tansent CHF ae nvestgated nt detals. And the pwe tansent CHF celatns aganst nlet and utlet subclngs f the test tubes wth twsted-tape nset ae deved due t the effect f blng numbe based n swl velcty, B c,sw, and Webe numbe based n swl velcty, We sw [10-13]. B B ( L / d ) L C Re d C c,sw C1D* Wesw e Sc* p* f nlet subclng s knwn (T sub,n40 K) (1) d L c,sw D* Wesw Sc p* f utlet subclng s knwn (T sub,ut30 K) () d whee B c,sw qc,sub,st ( d 4wT ) y (3) Gh 0. 5 d ( 4y ) fg We sw 0. 5 G d 4 4 d ( y ) l d w y T (4) C 1=0.08, C =0.53 and C 3=0.7 f L/daund 40 and C 1=0.09, C =0.85 and C 3=0.9 f L/daund 40. p*, w, T and y ae the nndmensnal expnental ped [u/{/g/( l- g)} 0.5 ], the wdth f the twsted-tape, the thckness f the twsted-tape and the twst at f the twsted-tape [H/d=(ptch f 180 tatn)/d], espectvely. Mst f the pwe tansent CHF data f SUS304-ccula tubes f d=6 mm wth the twsted-tapes f twst ats, y, f.40, 3.37 and 4.45 (186 pnts) ae wthn t 9.81 % dffeence f Eq. (1) and wthn -5. t % ne f Eq. () f the wde anges f nn-dmensnal expnental peds (p*=48.1 t ) and swl velctes (u sw=5.04 t 0.7 m/s). The bjectves f pesent study at a lss f flw accdent f Fusn React Safety (FRS) ae fvefld. Fst s t measue the tansent ctcal heat fluxes f SUS304-ccula tube wth vaus deceleatns caused by a apd decease n velcty () f the wde anges f ntal flw velctes (u 0), ntal heat fluxes (q 0) and nlet subclngs (T sub,n). Secnd s t cmpae the abve esults wth the pwe tansent ctcal heat fluxes f SUS304-ccula tubes wth and wthut twsted-tape nsets caused by apd nceasng heat nputs [10-18] (PT-CHF). Thd s t clafy the nfluence f ntal flw velcty, ntal heat flux, nlet subclng and deceleatn caused by a apd decease n velcty n the flw tansent ctcal heat flux (FT-CHF). Futh s t deve the celatns f flw velcty and CHF at the flw tansent ctcal heat flux n a ccula tube based n the expemental data. Ffth s t dscuss the mechansm f the subcled flw blng ctcal heat flux n a ccula tube. 3

5 EXPERIMENTAL APPARATUS AND METHOD Expemental Wate Lp The schematc dagam f expemental wate lp s shwn n Fg. 1. The lp s made f SUS304 stanless steel and s capable f wkng up t MPa. The lp has fve test sectns whse nne dametes ae, 3, 6, 9 and 1 mm. Test sectns wee vetcally ented wth wate flwng upwad. The test sectn f the nne damete f 6 mm was used n ths wk. The cculatng wate was dstlled and denzed wth abut 0.-S/cm specfc esstvty. The cculatng wate thugh the lp was heated cled t keep a desed nlet tempeatue by pe-heate cle. The mass velcty was measued by a mass flw mete usng a vbatn tube (Ntt Sek, CLEANFLOW 63FS5, Flw ange=100 and 750 kg/mn). The mass velcty was cntlled by egulatng the fequency f the thee-phase altenatng pwe suce t the multstage canned-type cculatn pump wth hgh pump head (Nkks C., Ltd., Nn- Seal Pump Mult-stage Type VNH1-C4 C-3S7SP, pump flw ate=1 m 3 /h, pump head=50 m) wth an nvete nstalled a 4-dgt LED mnt (Mtsubsh Electc Cp., Invete, Mdel-F70-30K). The pump nput fequency shws the net pump nput pwe and pump dschage pessue fee f slp lss. The cculatng wate was pessuzed by satuated vap n the pessuze n ths wk. The pessue at the utlet f the test tube was cntlled wthn 1 kpa f a desed value by usng a heate cntlle f the pessuze. Test Sectn The css-sectnal vew f 6 mm nne damete test sectn used n ths wk s shwn n Fg.. The SUS304 test tubes wth 3 dffeent suface ughnesses have been geneally used. The test tubes wth ugh and smth fnshed nne sufaces (RF and SF) ae cmmecally avalable. The ugh fnshed nne suface was fabcated by annealng the test tube fst n the atmsphee f a and was then acdzed. The ugh fnshed nne suface test tube (RF) was used n ths wk. The SUS304 ccula tubes f the test tube nne damete f 6 mm and the heated lengths, L, f 59.5 t 59.7 mm wee manly used. Wall thckness f the test tube,, was 0.5 mm. Tw fne 0.07-mm damete platnum wes wee spt-welded n the ute suface f the test tube as ptental taps. The effectve lengths, L eff, f the test tube between the ptental taps n whch heat tansfe was measued wee 48.7 t 50. mm. The slve-cated 5- mm thckness cppe-electde-plates t supply heatng cuent wee sldeed t the sufaces f the bth ends f the test tube. The bth ends f test tube wee electcally slated fm the lp by Bakelte plates f 14-mm thckness. The ute suface cndtn f the test tube was expsed t the atmsphee due t supptng tw fne ptental taps n ths wk. The nne suface cndtn f the test tube was bseved by the scannng electn mcscpe (SEM) phtgaph (JEOL JXA8600) and nne suface ughness was measued by Tky Semtsu C., Ltd. s suface textue measung nstument (SURFCOM 10A). Fgue 3 shws the SEM phtgaph f the 4

6 SUS304 test tube f d=6 mm wth the ugh fnshed nne suface (RF). The nne suface ughness s measued 3.89 m f Ra, 1.4 m f Rmax and m f Rz. Methd f Heatng Test Tube The test tube has been heated wth a fxed heat nput suppled fm a dect cuent suce (Takasag Ltd., NL R, DC 35 V-3000 A) thugh the tw cppe electdes shwn n Fg. 4. The cmmn specfcatns f the dect cuent suce ae as fllws. Cnstant-vltage (CV) mde egulatn s %+3 mv f full scale, CV mde pple s 500 V.m.s. bette and CV mde tansent espnse tme s less than 00 sec (Typcal) aganst 5 % t full ange change f lad. The flw tansent CHFs, q c,sub, wee ealzed by a apd decease n flw velcty fm nn-blng egme n the test tube. At the flw tansent CHF, the test tube aveage tempeatue apdly nceases. The cuent f the heat nput t the test tube was autmatcally cut ff when the measued aveage tempeatue nceased up t the peset tempeatue, whch was seveal tens f Kelvn hghe than cespndng flw tansent CHF suface tempeatue. Ths pcedue avded actual bunut f the test tube. Measuement f Flw Tansent CHF, Tempeatue and Pessue f Test Tube The flw tansent aveage tempeatue f the test tube, T (t), was measued wth esstance themmety patcpatng as a banch f a duble bdge ccut f the tempeatue measuement. The utput vltages fm the bdge ccut, V T(t), tgethe wth the vltage dp acss the ptental taps f the test tube, V R(t)=I(t)R T(t), and acss a standad esstance, V I(t)=I(t)R s, wee amplfed and then wee sent va a D/A cnvete t a dgtal cmpute. The unbalance vltage, V T(t), s expessed by means f Ohm s lw as the fllwng fm. I(t){ RT (t) R R1 R3 } VT (t) (5) R R 3 These vltages wee smultaneusly sampled at a cnstant nteval angng fm 10 s t 00 ms. The aveage tempeatue f the test tube between the ptental taps was calculated wth the ad f pevusly calbated esstance-tempeatue elatn, R T(t)=a(1+b T (t) + c T(t) ). The aveage tempeatues f the test tube between the tw electdes, V R1(t), wee cmpaed wth thse between ptental taps, V R(t), and much dffeence f a heat lss culd nt be clealy bseved n hgh subclng ange. The heat geneatn ate, Q(t)=I (t)r T(t), n the test tube between the ptental taps was calculated fm the measued vltage dffeence between the ptental taps f the test tube and the standad esstance, V R(t) and V I(t). The suface heat flux, q(t), s the dffeence between the heat geneatn ate pe unt suface aea, Q(t), and the ate f change f enegy stage n the test tube btaned 5

7 fm the faed aveage tempeatue vesus tme cuve as fllws: V dt ( t ) q( t ) Q( t ) c (6) S dt whee, c, V and S ae the densty, the specfc heat, the vlume and the nne suface aea f the test tube, espectvely. The heate nne suface tempeatues between the tw ptental taps, T s(t), wee als btaned by slvng the unsteady heat cnductn equatn n the test tube unde the cndtns f measued aveage tempeatue, T (t), and heat geneatn ate pe unt suface aea, Q(t), f the test tube. All the calculatns f the nne suface tempeatue wee made by usng the PHOENICS cde [19]. Basc unsteady tw-dmensnal heat cnductn equatn f the test tube s as fllws: T c t 1 T 1 T Q( t ) (7) The calculatn dman fm test tube nne adus,, t test tube ute adus,, s adally dvded nt 500 gd pnts (=1 m) and the tme step, t, s gven much smalle than 0.45 ms. The unsteady equatn s numecally analyzed tgethe wth the fllwng bunday cndtns. q( t ) T (8) T 0 (9) Futheme, the steady-state nne and ute suface tempeatues, T s and T s, wee als btaned by slvng the heat cnductn equatn n the test tube unde the cndtns f measued aveage tempeatue, T, and suface heat flux, q, f the test tube. The slutns f the nne and ute suface tempeatues f the test tube, T s and T s, ae gven by the steady ne-dmensnal heat cnductn equatn. The basc equatn f the test tube s as fllws: d d T 1 dt d Q 0 (10) then ntegatn yelds and the mean tempeatue f the test tube s btaned. T Q Q ln C 4 (11) T 1 T d (1) Geneatng heat n the tube s equal t the heat cnductn and the test tube s pefectly nsulated. 6

8 7 Q d dt q (13) 0 d dt (14) The tempeatues f the heate nne and ute sufaces, T s and T s, and C n Eq. (11) can be descbed by the steady ne-dmensnal heat cnductn equatn as fllws: s ln ) ( q ln ln ) ( q T ) T( T (15) s ln ) ( q ln ln ) ( q T ) T( T (16) ln ln ) ( q T C (17) whee T, q,, and ae aveage tempeatue f the test tube, heat flux, themal cnductvty, test tube nne adus and test tube ute adus, espectvely. In case f the 6 mm nne damete test sectn, befe enteng the test tube, the test wate flws thugh the tube wth the same nne damete f the test tube t fm the fully develped velcty pfle. The entance tube length, l e, s gven 333 mm (l e/d=55.5). The values f l e/d f d=6 mm n whch the cente lne velcty eaches 99 % f the maxmum value f tubulence flw wee btaned angng fm 9.8 t 1.9 by the celatn f Bdkey and Heshey [0] as fllws: / d e Re. d l (18) The nlet and utlet lqud tempeatues wee measued by 1-mm.d., sheathed, K-type themcuples (Nmblx, sheath mateal: SUS316, ht junctn: gund, espnse tme (63. %): 46.5 ms) whch ae lcated at the centelne f the tube at the uppe and lwe steam pnts f 83 and 63 mm fm the test tube nlet and utlet pnts. The nlet and utlet pessues wee measued by the stan gauge tansduces (Kywa Electnc Instuments C., Ltd., PHS-0A, Natual fequency: appxmately 30 khz), whch wee lcated nea the entance f cndut at uppe and lwe steam pnts f 63 mm fm the test tube nlet and utlet pnts. The themcuples and the tansduces wee nstalled n the cnduts as shwn n Fg.. The nlet and utlet pessues wee calculated fm the pessues measued by nlet and utlet pessue tansduces as fllws:

9 P P n ut P P Lpt Ppt pt wnh pt (19) wnh L L L pt pt pt L Pn Pn Ppt (0) L L whee L pt=0.063 m and L pt=0.063 m. Expemental es ae estmated t be 1 K n nne tube suface tempeatue and % n heat flux. Mass velcty, nlet and utlet subclngs, nlet and utlet pessues and deceleatn caused by a apd decease n velcty wee measued wthn the accuacy, 1 K, 4 kpa and %, espectvely. Flw tansent CHF expements at a lss f flw wee pefmed as fllws. Lqud level n the pessuze was adjusted t abut 400 mm fm the bttm f the vessel. Pessue f the test lp was kept cnstant at aund 800 kpa by satuated vap heated n the pessuze. The cculatn pump cntlled by an nvete was tun n and the pump nput fequency (f p) kept cnstant at a flw velcty, u, f 4.0 m/s. Inlet lqud tempeatue n the test lp was ased and kept cnstant at the desed value f angng fm 90 t 308 K by usng the pe-heate cle. Fst f all steady-state ctcal heat fluxes n a ccula test tube caused by expnentally nceasng heat nput (Q 0 exp(t/), =aund 8 s) wee measued. Then, the ntal pump nput fequency (f p0) was ased and kept cnstant at a ntal flw velctes (u 0=6.9, m/s) and electc cuent t the test tube was gadually ased t a desed heat geneatn ate level whch s the value f CHF measued by expnentally nceasng heat nput at the flw velcty f 4 m/s. Then the pump nput fequency was lnealy educed t 0 Hz f a deceleatn tme settng, t d, angng fm 0 t 00 secnds by the nvete functn (apdly t gadually). Schematc dagam f tme vaatns n pump nput fequency and flw velcty f flw tansent CHF expement ae shwn n Fg. 5. The heat geneatn ate, Q(t)=I (t)r T(t), n the test tube was kept cnstant f 144 ms t 40 s dung whch the measuements wee made n the tme ntevals f 10 s t 00 ms (100 pnts) at each deceleatn caused by a apd decease n velcty. EXPERIMENTAL RESULTS AND DISCUSSION Expemental Cndtns Flw tansent heat tansfe pcesses and CHFs that caused by a apd decease n velcty, u(t)=u 0-t, wee measued f the SUS304-ccula tube. The deceleatn caused by a apd decease n velcty () anged fm t m/s. The ntal expemental cndtns such as mass velcty, nlet subclng, utlet pessue and ntal heat flux n flw tansent heat tansfe and CHF expements wth vaus deceleatns caused by a apd decease n velcty wee detemned ndependently each the befe 8

10 each expemental un. The expemental cndtns wee as fllws: Test Tube Numbe Test Tube Mateal Inne Damete (d) Heated Length (L) Effectve Length (L eff) THD-F191 t THD-F196 SUS304 6 mm 59.5 t 59.7 mm 48.7 t 50. mm L/d 9.9 t 9.95 L eff/d 8.1 t 8.37 Wall Thckness () Suface Cndtn Suface Rughness Mass Velcty (G) Intal Flw Velcty (u 0) Inlet Pessue (P n) Outlet Pessue (P ut) Inlet Subclng (T sub,n) Outlet Subclng (T sub,ut) Inlet Lqud Tempeatue (T n) 0.5 mm Rugh fnshed nne suface (cmmecal fnsh) 3.89 m f Ra, 1.4 m f Rmax and m f Rz 0 t kg/m s t m/s f cndtns f u 0=6.9, 9.9 and 13.3 m/s t kpa t kpa t K t K 90.1 t K Intal heat flux (q 0) t MW/m Deceleatn caused by a Rapd Decease n Velcty () t m/s Steady-state Subcled Flw Blng CHF Chaactestcs [1-3] Outlet subclng: Fgue 6 shws the steady-state CHFs, q c,sub,st, vesus the utlet subclngs, T sub,ut, f the HORIZONTAL SUS304 ccula test tube f the nne damete (d=6 mm), the heated length (L=59.4 mm), L/d (=9.9) and the wall thckness (=0.5 mm) btaned f the flw velctes, u, angng fm 4 t 13.3 m/s at the utlet pessue, P ut, f aund 800 kpa. The CHF data f the VERTICAL SUS304 test tube f d=6 mm, L=66 mm, L/d=11 and =0.5 mm wth the flw velctes angng fm 4.0 t 13.3 m/s ae als shwn n the fgue f cmpasn []. As shwn n the fgue, the q c,sub,st f each flw velcty becme 9

11 hghe wth an ncease n T sub,ut and the nceasng ate becmes lwe f hghe T sub,ut. The CHFs n the whle expemental ange becme hghe wth an ncease n the flw velcty at a fxed T sub,ut. The cuves gven by the steady-state CHF celatn aganst utlet subclng, Eq. (1), f the VERTICAL SUS304 ccula test tube ae shwn n Fg. 6 at each flw velcty f cmpasn. The expnental peds,, f the heat nput, Q=Q 0 exp(t/), anged fm 6.55 t 1.81 s. B c L D* We Sc f T sub,ut30 K and u13.3 m/s (1) d C 1=0.08, C =0.53 and C 3=0.7 f L/daund 40 and C 1=0.09, C =0.85 and C 3=0.9 f L/daund 40. The CHF data f T sub,ut30 K ae n gd ageement wth the values gven by the celatn. Equatn (1) was deved based n the expemental data f the VERTICAL SUS304 test tube wth the flw velcty angng fm 4 t 13.3 m/s. T cnfm the applcablty f Eq. (1) t the data f the flw velcty f 4 t 13.3 m/s, the ats f these CHF data t the cespndng values calculated by Eq. (1) ae shwn vesus T sub,ut n Fg. 7. Mst f the data f the HORIZONTAL ccula test tube (69 pnts) and the VERTICAL ne (110 pnts) ae wthn 15 % dffeence f 4 m/su13.3 m/s and 9.7 KT sub,ut15.38 K. Inlet subclng: It can be cnsdeed that the CHFs ae detemned nt by the utlet cndtns but by the nlet nes. The steady-state CHFs, q c,sub,st, f the HORIZONTAL SUS304 ccula test tube f the nne damete f 6 mm, L=59.4 mm, L/d=9.9 and =0.5 mm wee shwn vesus the nlet subclng, T sub,n, wth the flw velctes f 4 t 13.3 m/s n Fg. 8. The CHF data f the VERTICAL SUS304 test tube f d=6 mm, L=66 mm, L/d=11 and =0.5 mm wth the flw velctes angng fm 4.0 t 13.3 m/s ae als shwn n the fgue f cmpasn [3]. The q c,sub,st f each flw velcty becme hghe wth an ncease n T sub,n. The nceasng ate becmes als lwe f hghe T sub,n. The q c,sub,st ncease wth an ncease n the flw velcty at a fxed T sub,n. The 0.7 q c,sub,st f the wde ange f flw velctes ae pptnal t T sub,n f T sub,n40 K. The cuves deved fm the steady-state CHF celatns aganst nlet subclng, Eq. (), f the VERTICAL SUS304 ccula test tube ae shwn n Fg. 8 f cmpasn. B ( L / d ) L C Re d C3 c C1D* We e Sc* f T sub,n40 K and u13.3 m/s () d The CHF data f T sub,n40 K ae n gd ageement wth the values gven by auths celatn. T cnfm the applcablty f Eq. (), the ats f these CHF data f the d=6 mm HORIZONTAL ccula test tube (69 pnts) and thse f the d=6 mm VERTICAL ne (110 pnts) t the cespndng values calculated by Eq. () ae shwn vesus T sub,n n Fg. 9. Mst f the data f T sub,n40 K ae wthn 15 % dffeence f Eq. () f the wde anges f nlet subclngs and flw velctes. 10

12 Flw Tansent CHF Chaactestcs (Cuent Study) In case f ntal flw velcty, u0, f 6.9 m/s at ntal heat Flux, q0=(qc,sub,st)u=4m/s: Fgue 10 shws typcal example f the tme vaatns n the nlet and utlet pessues, P n and P ut, the nlet and utlet lqud tempeatues, T n and T ut, heate nne suface tempeatue, T s, heat flux, q, and nlet flw velcty, u, f the ntal flw velcty, u 0=7.09 m/s, the ntal heat flux, q 0=15.73 MW/m, whch s equvalent t the CHF measued by expnentally nceasng heat nput (Q 0 exp(t/), =aund 8 s) at the flw velcty f 4 m/s and deceleatn caused by a apd decease n velcty, = m/s, at ntal utlet pessue, P ut0= kpa, ntal nlet subclng, T sub,n0= K. The values f P n, P ut, T n, T ut, T s, q and u keep almst cnstant untl the begnnng f a decease n flw velcty. The pump nput fequency was lnealy educed t 0 Hz at a deceleatn tme settng, t d, f 0 secnds by the nvete functn. As sn as the nlet flw velcty deceases, the P n and P ut scllate vlently and the T s and T ut have stated t ncease. At the elapsed tme f 6.35 secnds, that s, the flw tansent CHF pnt, the heate nne suface tempeatue, T s, apdly nceases, althugh the heat flux, q c,sub, ppstely deceases at the flw tansent CHF. The cuent f the heat nput t the test tube was autmatcally cut ff when the measued aveage tempeatue nceased up t the peset tempeatue, whch was seveal tens f Kelvn hghe than cespndng flw tansent CHF suface tempeatue. Ths pcedue avded actual bunut f the test tube. The heat flux, the utlet pessue, P ut, the flw velcty, u c, and the deceleatn caused by a apd decease n velcty,, at the flw tansent CHF wee measued MW/m, kpa, 4.56 m/s and m/s n ths un. Fgue 11 shws the tme vaatns n P n, P ut, T n, T ut, T s, q and u f the u 0=7.10 m/s, q 0=15.81 MW/m and = m/s, at P ut0= kpa, T sub,n0= K. The values f P n, P ut, T n, T ut, T s, q and u keep als cnstant untl the begnnng f a decease n flw velcty. The pump nput fequency was lnealy educed t 0 Hz at a deceleatn tme settng f 0 secnd by the nvete functn. The heat flux, the utlet pessue, the flw velcty and the deceleatn caused by a apd decease n velcty at the flw tansent CHF wee measued MW/m, kpa, 6.69 m/s and m/s n ths un. The flw velcty at the flw tansent CHF pnt becmes 46.7 % hghe (fm 4.56 t 6.69 m/s) wth a decease n the deceleatn caused by a apd decease n velcty,, fm t m/s at the ntal flw velcty, u 0=7.09 m/s. In case f ntal flw velcty, u0, f 9.9 m/s at ntal heat Flux, q0=(qc,sub,st)u=4m/s: Fgues 1 and 13 shw typcal examples f the tme vaatns n P n, P ut, T n, T ut, T s, q and u f u 0=10.09 and m/s, q 0=16.78 and MW/m and =-3.60 and m/s wth the deceleatn tme settng 10 and 0 secnds at P ut0=89.89 and kpa, and T sub,n0= and K, espectvely. The values f P n, P ut, T n, T ut, T s, q and u keep als cnstant untl the begnnng f a decease n flw velcty. The heat fluxes, the utlet pessues, the flw velctes and the deceleatns caused by a apd decease n velcty at the flw tansent CHF 11

13 wee measued and MW/m, and kpa, 6.09 and 8.61 m/s, and -3.6 and m/s n these uns, espectvely. The flw velcty at the flw tansent CHF pnt becmes 41.4 % hghe (fm 6.09 t 8.61 m/s) wth a decease n the deceleatn caused by a apd decease n velcty fm -3.6 t m/s at the ntal flw velcty, u 0=10.09 m/s. In case f ntal flw velcty, u0, f 13.3 m/s at ntal heat Flux, q0=(qc,sub,st)u=4m/s: Fgues 14 and 15 shw typcal examples f the tme vaatns n P n, P ut, T n, T ut, T s, q and u f u 0=13.30 and 13.6 m/s, q 0=16.6 and MW/m and = and m/s f the deceleatn tme settng 7 and secnds at P ut0=84.63 and kpa, and T sub,n0=155.1 and K, espectvely. The values f P n, P ut, T n, T ut, T s, q and u keep als cnstant untl the begnnng f a decease n flw velcty. The heat fluxes, the utlet pessues, the flw velctes and the deceleatns caused by a apd decease n velcty at the flw tansent CHF wee measued and MW/m, and kpa, 7.0 and m/s, and and m/s n these uns, espectvely. The flw velcty at the flw tansent CHF pnt becmes 44.6 % hghe (fm 7.0 t m/s) wth a decease n the deceleatn caused by a apd decease n velcty fm t m/s at the ntal flw velcty, u 0=13.30 m/s. F pwe tansent CHF expements, the ate f nceasng heat nput s vey hgh. It takes tme t fm the fully develped tempeatue pfle n the test tube because the test tube has sme heat capacty. Then the tempeatue pfle n the cnductve sublaye n the test tube suface gws, and vapzatn ccus. It als takes sme tme t ccu nstantaneusly the hetegeneus spntaneus nucleatn n the test tube suface at the pwe tansent CHF. Namely, t s explaned t be as a esult f the tme-lag f the fmatn f the pwe tansent CHF f the nceasng ate f the heat nput. Hweve, f flw tansent CHF expements, the devatns fm the adal flw velcty f sthemal flw ae a esult f the fact that the decease n flw velcty advances at the vcnty f the tube suface n the test sectn and s late at the cente f the tube n the test sectn by nteactn f a tube wall suface and the test wate n the vscsty. Namely, t s explaned t be as a esult f the nn-unfm f the deceasng ate f the adal flw velcty f the fmatn f the flw tansent CHF. The flw tansent CHFs, q c,sub, at the ntal heat flux, q 0=(q c,sub,st) u=4m/s, whch s equvalent t the CHF measued by expnentally nceasng heat nput (Q 0 exp(t/), =aund 8 s) at the flw velcty f 4 m/s, f the deceleatns caused by a apd decease n velcty,, angng fm m/s t m/s ae shwn as geen, ange and sky-blue pen ccle symbls wth the ntal flw velctes, u 0, f 6.9, 9.9 and 13.3 m/s, espectvely, n Fgs. 6 t 9. Mst f the flw tansent CHF data ae wthn t 15.4 % and t 0.55 % dffeences f the values calculated fm the steady-state CHF celatns aganst utlet and nlet subclngs f the ccula test tube, Eqs. (1) and (), espectvely. Fgue 16 shws a typcal phtgaph f SUS304 test tubes f d=6 mm and L=59.7 mm wth the test tube numbes f THD-F19 1

14 and THD-F194 buned ut n flw tansent CHF expements. The dak sectns n the mddle t utlet f the test tube ae the taces f the vap patches whch wuld have becme hgh tempeatue; the lcal tempeatues n the tube jumped t thse f the flm blng egn at the ccuence f flw tansent CHF. The lcatns f these vap patches wee almst bseved n the mddle t utlet f the test tube n ths flw tansent CHF expement. It s assumed that the tanstn t flm blng n ths wk wuld ccu by tw mechansms f the subcled flw blng ctcal heat flux: ne s due t the hyd-dynamc nstablty at an utlet aea f the test tube and the the s due t the hetegeneus spntaneus nucleatn at the lwe lmt f the hetegeneus spntaneus nucleatn tempeatue at a mddle aea f the test tube. The tube wall dd nt clealy melt dwn alng the ccumfeence f the tube, because the heatng cuent t the tube was nstantaneusly cut ff when the measued aveage tempeatue apdly nceased up t the peset tempeatue lwe than the actual bunut tempeatue f the tube. By usng ths bunut detect, seveal CHF data wee btaned f a sngle tube wthut the actual bunut. Celatns f Flw Velcty and CHF at Flw Tansent CHF The expemental esults f the flw tansent CHFs f d=6 mm nne damete at the ntal heat flux, q 0=(q c,sub,st) u=4m/s, whch s equvalent t the CHF measued by expnentally nceasng heat nput (Q 0 exp(t/), =aund 8 s) at the flw velcty f 4 m/s wth the ntal flw velctes, u 0, f 6.9, 9.9 and 13.3 m/s ae shwn n Fg. 17 n the flw velcty at flw tansent CHF, u c, vesus the deceleatn caused by a apd decease n velcty,, gaph and n the flw tansent CHF, q c,sub, vesus gaph wth the ntal flw velcty as a paamete. The u c becme lnealy hghe wth the decease n the fm aund -1 m/s and ae cnstant f the geate than -1 m/s and equvalent t 4 m/s. The slpes n the lnea gaph ae almst cnstant abut -1.0 s f the angng fm t -1 m/s and 0 s f the angng fm -1 t m/s, espectvely. These data f the flw velcty at flw tansent CHF, u c, can be expessed by the fllwng empcal celatns based n the expemental data. u 3 f -1 m/s (3) c u 4 f -1 m/s m/s (4) q c c, sub q 0 f m/s (5) The celatns can descbe the flw tansent CHF data (60 pnts) f d=6 mm wth the u 0=6.9, 9.9 and 13.3 m/s at a desed heat flux level whch s equvalent t the CHF measued by expnentally nceasng heat nput (Q 0 exp(t/), =aund 8 s) at the flw velcty f 4 m/s, q 0=(q c,sub,st) u=4m/s, btaned n ths wk wthn 0 % dffeence unde m/s m/s as shwn n Fg

15 In ths study, t s fmly cnfmed that the steady-state CHF celatns aganst utlet and nlet subclngs, Eqs. (1) and (), can delneate nt nly the auths publshed CHF data (306 pnts) f the HORIZONTAL and VERTICAL SUS304 test tubes wth the wde anges f nlet pessues (P n=159 kpa t 1.1 MPa), nne dametes (d= t 1 mm), heated lengths (L= t 150 mm) and flw velctes (u=4.0 t 13.3 m/s) [4-3] wthn 15 % dffeence f 30 KT sub,ut140 K and 40 KT sub,n151 K but als the flw tansent CHF f the ccula tube f 6 mm nne damete btaned n ths wk wthn t 15.4 % and t 0.55 % dffeences, espectvely. We have suppsed that the expessns f flw velcty map (u c/u c,st vesus ) and ctcal heat flux ne (q c,sub/q 0 vesus ) at flw tansent CHF aganst steady-state ctcal heat flux wuld be vey useful t dscuss the mechansm f the tansent ctcal heat flux f subcled wate flw blng caused by a apd decease n velcty, whch wuld ccu due t the hyddynamc nstablty suggested by Kutateladze [33] and Zube [34] due t the hetegeneus spntaneus nucleatn at the lwe lmt f the hetegeneus spntaneus nucleatn tempeatue [35]. The ats f flw velcty at flw tansent CHF pnt t flw velcty calculated fm Eq. () wth ntal heat flux, q 0, by a ty-and-e methd, u c/u c,st, and thse f flw tansent CHF, q c,sub=q 0, t steady-state ctcal heat flux calculated fm Eq. () wth the flw velcty at flw tansent CHF pnt, (q c,sub/q c,sub,st), f the SUS304 ccula test tube f d=6 mm and L=59.5 t 59.7 mm wth nlet lqud tempeatues, T n, f 90.1 t K at the ntal flw velctes, u 0, f 6.9, 9.9 and 13.3 m/s ae shwn vesus the deceleatn caused by a apd decease n velcty,, at ntal heat flux, q 0, whch s equvalent t the CHF at the flw velcty f 4 m/s, (q c,sub,st) u=4m/s, n Fg. 18. The expemental data f u c/u c,st and q c,sub/q c,sub,st f the SUS304 test tube f d=6 mm wth the ugh fnshed nne suface can be expessed f the angng fm t m/s by the fllwng celatns: u u c c,st f m/s (6) u u c c,st 1 f m/s m/s (7) q q c,sub c,sub,st f m/s (8) q q c,sub c,sub,st 1 f m/s m/s (9) It s assumed that the tanstn t flm blng at the deceleatn caused by a apd decease n velcty,, lwe than -5 m/s wuld ccu due t the hetegeneus spntaneus nucleatn but nt due t the hyd-dynamc nstablty. The auths publshed CHF data (306 pnts) f the HORIZONTAL and VERTICAL SUS304 test tubes wth the wde anges f nlet pessues (P n=159 kpa t

16 MPa), nne dametes (d= t 1 mm), heated lengths (L= t 150 mm) and flw velctes (u=4.0 t 13.3 m/s) [4-3] have been measued. In Fgs. 19 (a) and (b), the dak sectns n the utlet alne f the test tube ae the taces f the vap patches whch wuld have becme hgh tempeatue; the lcal tempeatues n the tube jumped t thse f the flm blng egn at the ccuence f steady-state CHF whch wuld ccu due t the hyddynamc nstablty suggested by Kutateladze [33] and Zube [34]. The utlet lqud tempeatue and pessue, T ut and P ut, becme hghe and lwe espectvely and utlet subclng, T sub,ut, des lwe, s the tanstn t flm ccu at the utlet f the test tube n the fst place. In ths flw tansent CHF expement, the lcatns f these vap patches due t the hyddynamc nstablty wuld be nmally bseved n the utlet f the test tube at the deceleatn caused by a apd decease n velcty,, hghe than -5 m/s and thse due t the hetegeneus spntaneus nucleatn at the lwe lmt f the hetegeneus spntaneus nucleatn tempeatue wuld be bseved n the mddle f the test tube at the lwe than -5 m/s. The dffeences between the lcatns f the vap patches n Fg. 16 and thse n Fgs. 19 (a) and (b) ae the easn that the flw tansent CHF wuld ccu due t the hetegeneus spntaneus nucleatn at the lwe lmt f the hetegeneus spntaneus nucleatn tempeatue f the apd flw tansent lwe than -5 m/s. And, Fgue 0 shws the q vesus u plts f the tansent blng heat tansfe pcesses n a d=6 mm nne damete f vaus deceleatns caused by a apd decease n velcty,, f -.15, -3.63, -5.08, -5.94, and m/s at a fxed ntal flw velcty, u 0, f 13.3 m/s. By cmpang the tansent heat tansfe pcesses f the f -.15, and m/s wth thse f -5.94, and m/s, t can be seen that the flw tansent ctcal heat flux f elatvely steep deceleatn caused by a apd decease n velcty s vey much affected by the deceasng ate. The tansent pcesses f the f -.15, and m/s successvely fllw a fxed heat flux wth the decease n the flw velcty and eaches the flw tansent ctcal heat flux, whch s expected fm the fgue t be almst n ageement wth the steady-state ctcal heat flux. On the cntay, thse f the f -5.94, and m/s fllw als a fxed heat flux wth the decease n the flw velcty and eaches the flw tansent ctcal heat flux, whch s seen fm the fgue t be abut -30 t 15 % f the steady-state ctcal heat flux. It s als assumed that the tanstn t flm blng n ths wk wuld ccu by tw mechansms f the flw tansent ctcal heat flux: the fme s due t the hyd-dynamc nstablty and the latte s due t the hetegeneus spntaneus nucleatn at the lwe lmt f the hetegeneus spntaneus nucleatn tempeatue. CONCLUSIONS The flw tansent ctcal heat fluxes (FT-CHFs) n a SUS304-ccula tube f nne damete (d=6 mm), heated length (L=59.5 t 59.7 mm), effectve length (L eff=48.7 t 50. mm), L/d (=9.9 t 9.95), L eff/d (=8.1 t 8.37) and wall thckness (=0.5 mm) caused by a apd decease n velcty fm nn-blng egme ae systematcally measued f ntal flw velctes (u 0=7.057 t m/s f 15

17 cndtns f u 0=6.9, 9.9 and 13.3 m/s), ntal heat fluxes (q 0=15.59 t MW/m ), nlet lqud tempeatues (T n=90.1 t K), utlet pessues (P ut= t kpa) and deceleatns caused by a apd decease n velcty (u(t)=u 0+t, = t m/s ). Expemental esults lead t the fllwng cnclusns. 1) As sn as the nlet flw velcty deceases, the P n and P ut scllate vlently and the T s and T ut have stated t ncease. At the flw tansent CHF pnt, the heate nne suface tempeatue, T s, apdly nceases, althugh the heat flux, q c,sub, ppstely deceases at the flw tansent CHF. ) Mst f the flw tansent CHF data ae wthn t 15.4 % and t 0.55 % dffeences f the values calculated fm the steady-state CHF celatns aganst utlet and nlet subclngs f the ccula test tube, Eqs. (1) and (), espectvely. 3) The flw velcty at the flw tansent CHF pnt, u c, becmes lnealy hghe wth a decease n the deceleatn caused by a apd decease n velcty,, fm aund -1 m/s and ae cnstant f the geate than -1 m/s and equvalent t 4 m/s. 4) The slpes n the lnea gaph ae almst cnstant abut -1.0 s f the angng fm t -1 m/s and 0 s f the angng fm -1 t m/s, espectvely. These data f the flw velcty at flw tansent CHF, u c, can be expessed by the fllwng empcal celatns based n the expemental data. u 3 f -1 m/s (3) c u 4 f -1 m/s m/s (4) c q c, sub q 0 f -0.36m/s (5) 5) The expemental data f u c/u c,st and q c,sub/q c,sub,st f the SUS304 test tube f d=6 mm wth the ugh fnshed nne suface can be expessed f the angng fm t m/s by the fllwng celatns: u u c c,st f m/s (6) u u c c,st 1 f m/s m/s (7) q q c,sub c,sub,st f m/s (8) q q c,sub c,sub,st 1 f m/s m/s (9) 6) We have suppsed that the expessns f flw velcty map (u c/u c,st vesus ) and ctcal heat flux ne (q c,sub/q 0 vesus ) at flw tansent CHF aganst steady-state ctcal heat flux wuld be vey useful t dscuss the mechansm f the tansent ctcal heat flux 16

18 f subcled wate flw blng caused by a apd decease n velcty, whch wuld ccu due t the hyd-dynamc nstablty due t the hetegeneus spntaneus nucleatn at the lwe lmt f the hetegeneus spntaneus nucleatn tempeatue. It s assumed that the tanstn t flm blng at the deceleatn caused by a apd decease n velcty,, lwe than -5 m/s wuld ccu due t the hetegeneus spntaneus nucleatn but nt due t the hyd-dynamc nstablty. NOMENCLATURE a, b, c ftted cnstant B c =q c,sub/gh fg, blng numbe B c,sw q Gh c,sub,st fg ( d 4wT ) d ( 4y y 0. 5 ), blng numbe based n swl velcty C cnstant n Eqs. (11) C 1, C, C 3 cnstants n Eqs. (1) and () c p specfc heat at cnstant pessue, J/kg K D* =d/{/g/( l- g)} 0.5, nn-dmensnal damete d f p f p0 G test tube nne damete, m pump nput fequency, Hz ntal pump nput fequency, Hz = lu, mass velcty, kg/m s g acceleatn f gavty, m/s h fg I L L e L eff L pt L pt P P n latent heat f vapzatn, J/kg cuent flwng thugh standad esstance, A heated length, m entance length, m effectve length, m dstance between nlet pessue tansduce and nlet f the heated sectn, m dstance between utlet pessue tansduce and utlet f the heated sectn, m pessue, kpa pessue at nlet f heated sectn, kpa 17

19 P pt P ut P ut0 P pt pessue measued by nlet pessue tansduce, kpa pessue at utlet f heated sectn, kpa ntal utlet pessue, kpa pessue measued by utlet pessue tansduce, kpa p* =u/{/g/( l- g)} 0.5, nn-dmensnal expnental ped Q heat geneatn ate and heat nput pe unt vlume, W/m 3 Q 0 ntal expnental heat nput, W/m 3 q heat flux, W/m q 0 ntal heat flux, W/m q c,sub flw tansent CHF, W/m q c,sub,st steady-state CHF f subcled cndtn, W/m R 1 t R 3 Ra Rmax Rz esstance n a duble bdge ccut, aveage ughness, m maxmum ughness depth, m mean ughness depth, m adus, m test tube nne adus, m test tube ute adus, m S suface aea, m Sc Sc* T T T H T HET T n T ut =c plt sub,ut/h fg, nn-dmensnal utlet subclng =c plt sub,n/h fg, nn-dmensnal nlet subclng tempeatue f the test tube, K aveage tempeatue f the test tube, K hmgeneus spntaneus nucleatn tempeatue, K lwe lmt f hetegeneus spntaneus nucleatn tempeatue, K nlet lqud tempeatue, K utlet lqud tempeatue, K 18

20 T s t t d T sub,n T sub,n0 T sub,ut u u 0 u c heate nne suface tempeatue, K tme, s deceleatn tme settng, s =(T sat-t n), nlet subclng, K ntal nlet subclng, K =(T sat-t ut), utlet subclng, K nlet flw velcty, m/s ntal flw velcty, m/s flw velcty at the flw tansent CHF, m/s V vlume, m 3 V I V R V R1 V T We vltage dp acss standad esstance, V vltage dp acss tw ptental taps, V vltage dp acss tw electdes, V unbalance vltage n a duble bdge ccut, V =G d/ l, Webe numbe We sw w y 0. 5 G d 4 4 d ( y ), Webe numbe based n swl velcty l d w y T wdth f twsted-tape, m =H/d=(ptch f 180 tatn)/d, twst at f twsted-tape deceleatn caused by a apd decease n velcty, (m/s ) T wall thckness, mm thckness f twsted-tape, m themal cnductvty, W/mK vscsty, Ns/m densty, kg/m 3 suface tensn, N/m expnental ped, s 19

21 Subscpt c g n ut l sat sub wnh ctcal vap nlet utlet lqud satuated cndtn subcled cndtn wth n heatng ACKNOWLEDGMENTS Ths eseach was pefmed as a LHD jnt eseach pject f NIFS (Natnal Insttute f Fusn Scence), Japan, NIFS13KEMF054, 013 and 014. REFERENCES [1] Gambll, W. R., Bundy, R.D., and Wansbugh, R. W., 1961, "Heat Tansfe, Bunut, and Pessue Dp f Wate n Swl Flw Tubes wth Intenal Twsted Tapes," Chem. Eng. Pg. Symp. Se., 57 (3), pp [] Blatt, T. A., and Adt, R. R., 1963, "The Effects f Twsted Tape Swl Geneats n the Heat Tansfe Rate and Pessue Dp f Blng Fen 11 and Wate," ASME-63-WA-4. [3] Lpna, R. F., and Begles, A.E., 1973, "Subcled Blng f Wate n Tape Geneated Swl Flw," J. Heat Tansfe, 95, pp [4] Celata, G. P., 1993, "Recent Achevements n the Themal Hydaulcs f Hgh Heat Flux Cmpnents n Fusn Reacts," Expemental Themal and Flud Scence, 7, pp [5] Tng, W., Begles, A. E., and Jensen, M. K., 1996, "Ctcal Heat Flux and Pessue Dp f Subcled Flw Blng n Small- Damete Tubes wth Twsted-tape Insets," Junal f Enhanced Heat Tansfe, 3, N., pp [6] Kabata, Y., Nakajma, R., and Shda, K., 1996, "Enhancement f Ctcal Heat Flux f Subcled Flw Blng f Wate n Tubes wth a Twsted Tape and wth a Helcally Cled We," Pc. f the ASME-JSME 4th Intenatnal Cnfeence n Nuclea Engneeng, Bk N. I389A-1996, pp [7] Inasaka, F., and Naa, H., 1996, "Evaluatn f subcled ctcal heat flux celatns f tubes wth and wthut ntenal twsted 0

22 tapes," Nuclea Engneeng and Desgn, 163, pp [8] Manglk, R. M., and Begles, A. E., 00, Swl Flw Heat Tansfe and Pessue Dp wth Twsted-Tape Insets, Advances n Heat Tansfe, 36, Academc Pess, NewYk, pp [9] Bejan, A., and Kaus, A. D., 003, Heat Tansfe Handbk, Jhn Wley & Sns, p [10] Hata, K., Sha, Y., and Masuzak, S., 01, Tansent Ctcal Heat Fluxes f Subcled Wate Flw Blng n a Sht SUS304-Tube wth Twsted-Tape Inset, Pceedngs f the 0 th Intenatnal Cnfeence n Nuclea Engneeng & ASME 01 Pwe Cnfeence ICONE0POWER01, Pape N. ICONE0POWER01-541, pp [11] Hata, K., Sha, Y., and Masuzak, S., 013, Tansent Ctcal Heat Fluxes f Subcled Wate Flw Blng n a SUS304- CIRCULAR Tube wth Twsted-Tape Inset, Junal f Pwe and Enegy Systems, 7, N., pp [1] Hata, K., Sha, Y., and Masuzak, S., 013, Tansent Ctcal Heat Fluxes f Subcled Wate Flw Blng n a SUS304- Ccula Tube wth Vaus Twsted-Tape Insets (Influence f Twst Rat), Pceedngs f the 1 st Intenatnal Cnfeence n Nuclea Engneeng, July 9-August, 013, Chengdu, Chna, Pape N. ICONE1-1533, pp [13] Hata, K., Fukuda, K., and Masuzak, S., 014, Tansent Ctcal Heat Fluxes f Subcled Wate Flw Blng n a SUS304- Ccula Tube wth Vaus Twsted-Tape Insets (Influence f Twst Rat), Junal f Themal Scence and Engneeng Applcatns, Tans. ASME, 6, pp [14] Hata, K., and Masuzak, S., 011, Subcled Wate Flw Blng Heat Tansfe n a Sht SUS304-Tube wth Twsted-Tape Inset, Junal f Engneeng f Gas Tubnes and Pwe, Tans. ASME, 133, pp [15] Hata, K., and Masuzak, S., 011, Heat Tansfe and Ctcal Heat Flux f Subcled Wate Flw Blng n a SUS304-Tube wth Twsted-Tape Inset, Junal f Themal Scence and Engneeng Applcatns, Tans. ASME, 3, pp [16] Hata, K., and Masuzak, S., 011, Twsted-Tape- Induced Swl Flw Heat Tansfe and Pessue Dp n a Sht Ccula Tube unde Velctes Cntlled, Nuclea Engneeng and Desgn, 41, pp [17] Hata, K., and Nda, N., 008, "Tansent Ctcal Heat Fluxes f Subcled Wate Flw Blng n a Sht Vetcal Tube Caused by Expnentally Inceasng Heat Inputs," Junal f Heat Tansfe, Tans. ASME, Sees C, 130, pp [18] Hata, K., and Masuzak, S., 010, "Influence f Heat Input Wavefm n Tansent Ctcal Heat Flux f Subcled Wate Flw Blng n a Sht Vetcal Tube," Nuclea Engneeng and Desgn, 40, pp [19] Spaldng, D. B., 1991, The PHOENICS Begnne's Gude, CHAM Ltd., Lndn, Unted Kngdm. [0] Bdkey, R. S., and Heshey, H. C., 1988, Tanspt Phenmena, McGaw-Hll, New Yk, p [1] Hata, K., Sha, Y., and Masuzak, S., 013, Heat Tansfe and Ctcal Heat Flux f Subcled Wate Flw Blng n a 1

23 Hzntal Ccula Tube, Expemental Themal and Flud Scence, 44, pp [] Hata, K., Shtsu, M., and Nda, N., 004, "Ctcal Heat Fluxes f Subcled Wate Flw Blng aganst Outlet Subclng n Sht Vetcal Tube," Junal f Heat Tansfe, Tans. ASME, Sees C, 16, pp [3] Hata, K., Km, H., Shtsu, M., and Nda, N., 004, "Ctcal Heat Fluxes f Subcled Wate Flw Blng aganst Inlet Subclng n Sht Vetcal Tube," JSME Intenatnal Junal, Sees B, 47, N., pp [4] Hata, K., Shtsu, M., and Nda, N., 006, "Ctcal Heat Flux f Subcled Wate Flw Blng f Hgh L/d Regn," Nuclea Scence and Engneeng, 154, N. 1, pp [5] Hata, K., Shtsu, M., and Nda, N., 006, "Influence f Heatng Rate n Subcled Flw Blng Ctcal Heat Flux n a Sht Vetcal Tube," JSME Intenatnal Junal, Sees B, 49, N., pp [6] Hata, K., Shtsu, M., and Nda, N., 007, Influence f Test Tube Mateal n Subcled Flw Blng Ctcal Heat Flux n Sht Vetcal Tube, Junal f Pwe and Enegy Systems, 1, N. 1, pp [7] Hata, K., and Nda, N., 008, Tubulent Heat Tansfe f Heatng f Wate n a Sht Vetcal Tube, Junal f Pwe and Enegy Systems,, N. 1, pp [8] Hata, K., and Nda, N., 008, "Tansent Ctcal Heat Fluxes f Subcled Wate Flw Blng n a Sht Vetcal Tube Caused by Expnentally Inceasng Heat Inputs," Junal f Heat Tansfe, Tans. ASME, Sees C, 130, pp [9] Hata, K., and Masuzak, S., 009, Subcled Blng Heat Tansfe n a Sht Vetcal SUS304-Tube at Lqud Reynlds Numbe Range t , Nuclea Engneeng and Desgn, 39, pp [30] Hata, K., and Masuzak, S., 010, Subcled Blng Heat Tansfe f Tubulent Flw f Wate n a Sht Vetcal Tube, Junal f Heat Tansfe, Tans. ASME, Sees C, 13, pp [31] Hata, K., and Masuzak, S., 010, "Influence f Heat Input Wavefm n Tansent Ctcal Heat Flux f Subcled Wate Flw Blng n a Sht Vetcal Tube," Nuclea Engneeng and Desgn, 40, pp [3] Hata, K., and Masuzak, S., 010, "Ctcal Heat Fluxes f Subcled Wate Flw Blng n a Sht Vetcal Tube at Hgh Lqud Reynlds Numbe," Nuclea Engneeng and Desgn, 40, pp [33] Kutateladze, S.S., 1959, Heat Tansfe n Cndensatn and Blng, AEC-t-3770, USAEC. [34] Zube, N., 1959, Hyddynamc Aspects f Blng Heat Tansfe, AECU-4439, USAEC. [35] Cle, C., 1979, "Hmgeneus and hetegeneus nucleatn n Blng Phenmena," Vl. 1, Stalen, S. van, and Cle, R. eds., Hemsphee Pub. Cp., p. 71.

24 Fg. 1 Schematc dagam f expemental wate lp 3

25 Fg. Vetcal css-sectnal vew f 6 mm nne damete test sectn 4

26 Fg. 3 SEM phtgaph f the SUS304 test tube f d=6 mm wth the ugh fnshed nne suface 5

27 Fg. 4 Measuement and data pcessng system 6

28 Q (W/m 3 ), f p (Hz), u (m/s) Q 0 0 Flw Tansent Q(t)=Q u 0 0 f p (t)=0 f p0 f p (t)=f p0 -(f p0 /00)t u(t)=u t u(t)=u t Deceleatn tme settng 0 00 tme (s) Fg. 5 Tme vaatns n pump nput fequency and flw velcty f flw tansent CHF expement 7

29 q c,sub,st (MW/m ) Hzntal Oentatn SUS304 u RF 4.0 m/s d=6 mm 6.9 m/s L=59.4 mm 9.9 m/s L/d= m/s P ut =800 kpa Eq. (1) Eq. (1) Vetcal Oentatn d=6 mm L=66 mm L/d=11 u 4.0 m/s 6.9 m/s 9.9 m/s 13.3 m/s T sub,ut (K) Cuent Study Vetcal Oentatn d=6 mm L= mm L/d= P ut = kpa q 0 = (q c,sub,st ) u=4m/s u m/s 9.9 m/s 13.3 m/s Fg. 6 q c,sub,st vs. T sub,ut f an nne damete f 6mm wth the heated length f 59.5 t 59.7 mm at utlet pessues f t 870. kpa 8

30 (q c,sub,st ) exp /(q c,sub,st ) cal Hzntal Oentatn SUS304 u RF 4.0 m/s d=6 mm 6.9 m/s L=59.4 mm 9.9 m/s L/d= m/s P ut =800 kpa (q c,sub,st ) exp : expemental value (q c,sub,st ) cal : calculated value T sub,ut (K) +15% -15% Vetcal Oentatn d=6 mm L=66 mm L/d=11 u 4.0 m/s 6.9 m/s 9.9 m/s 13.3 m/s Cuent Study Vetcal Oentatn d=6 mm L= mm L/d= P ut = kpa q 0 = (q c,sub,st ) u=4m/s u m/s 9.9 m/s 13.3 m/s Fg. 7 Rats f CHF data f the nne damete f 6 mm t the values deved fm the utlet CHF celatn, Eq. (1), vesus T sub,ut at utlet pessues f t 870. kpa 9

31 q c,sub,st (MW/m ) Hzntal Oentatn SUS304 u RF 4.0 m/s d=6 mm 6.9 m/s L=59.4 mm 9.9 m/s L/d= m/s P n = kpa Eq. () Eq. () Vetcal Oentatn d=6 mm L=66 mm L/d= T sub,n (K) u 4.0 m/s 6.9 m/s 9.9 m/s 13.3 m/s Cuent Study Vetcal Oentatn d=6 mm L= mm L/d= P n = kpa q 0 = (q c,sub,st ) u=4m/s u m/s 9.9 m/s 13.3 m/s Fg. 8 q c,sub,st vs. T sub,n f an nne damete f 6mm wth the heated length f 59.5 t 59.7 mm at nlet pessues f t kpa 30

32 (q c,sub,st ) exp /(q c,sub,st ) cal Hzntal Oentatn SUS304 u (q c,sub,st ) exp : expemental value RF 4.0 m/s (q c,sub,st ) cal : calculated value d=6 mm 6.9 m/s L=59.4 mm 9.9 m/s L/d= m/s P n = kpa +15% -15% Vetctal Oentatn d=6 mm L=66 mm L/d= T sub,n (K) u 4.0 m/s 6.9 m/s 9.9 m/s 13.3 m/s Cuent Study Vetcal Oentatn d=6 mm L= mm L/d= P n = kpa q 0 = (q c,sub,st ) u=4m/s u m/s 9.9 m/s 13.3 m/s Fg. 9 Rats f CHF data f the nne damete f 6 mm t the values deved fm the nlet CHF celatn, Eq. (), vesus T sub,n at nlet pessues f t kpa 31

33 u (m/s), P n /100, P ut /100 (kpa) t d =0 s FT8359 SUS304 d=6 mm L=59.5 mm P n P ut u P ut =703.9 kpa T sub,n = K u=4.56 m/s = m/s T s q CHF pnt T ut T n tme (s) 1 q (MW/m ) T n, T ut, T s (K) Fg. 10 Tme vaatns n P n, P ut, T n, T ut, T s, q and u f u 0=7.09 m/s, q 0=15.73 MW/m and = m/s at P ut0= kpa and T sub,n0= K 3

34 u (m/s), P n /100, P ut /100 (kpa) t d =0 s P n P ut FT8360 u SUS304 T d=6 mm s q L=59.5 mm P ut =81.75 kpa T sub,n = K u=6.69 m/s = m/s T ut T n CHF pnt tme (s) 1 q (MW/m ) T n, T ut, T s (K) Fg. 11 Tme vaatns n P n, P ut, T n, T ut, T s, q and u f u 0=7.10 m/s, q 0=15.81 MW/m and = m/s at P ut0= kpa and T sub,n0= K 33

35 u (m/s), P n /100, P ut /100 (kpa) u t d =10 s P n P ut FT8399 SUS304 q d=6 mm L=59.7 mm P ut = kpa T sub,n = K u=6.09 m/s =-3.60 m/s T s CHF pnt T ut T n tme (s) 1 q (MW/m ) T n, T ut, T s (K) Fg. 1 Tme vaatns n P n, P ut, T n, T ut, T s, q and u f u 0=10.09 m/s, q 0=16.78 MW/m and =-3.60 m/s at P ut0=89.89 kpa and T sub,n0= K 34

36 u (m/s), P n /100, P ut /100 (kpa) t d =0 s FT8401 SUS304 d=6 mm L=59.7 mm P ut =73.48 kpa T sub,n = K u=8.61 m/s = m/s u P n P ut q T s CHF pnt T ut T n tme (s) 1 q (MW/m ) T n, T ut, T s (K) Fg. 13 Tme vaatns n P n, P ut, T n, T ut, T s, q and u f, u 0=10.08 m/s, q 0=16.70 MW/m and = m/s at P ut0=830.6 kpa and T sub,n0= K 35

37 u (m/s), P n /100, P ut /100 (kpa) FT8434 t d =7 s SUS304 d=6 mm L=59.7 mm P ut =791.9 kpa T sub,n = K u=7.0 m/s = m/s u q T s P n P ut T ut CHF pnt T n tme (s) q (MW/m ) T n, T ut, T s (K) Fg. 14 Tme vaatns n P n, P ut, T n, T ut, T s, q and u f u 0=13.30 m/s, q 0=16.6 MW/m and = m/s at P ut0=84.63 kpa and T sub,n0=155.1 K 36

38 u (m/s), P n /100, P ut /100 (kpa) FT843 t d = s SUS304 d=6 mm L=59.7 mm P ut = kpa T sub,n = K u=10.41 m/s = m/s u P n P ut T s T n tme (s) q CHF pnt T ut 1 q (MW/m ) T n, T ut, T s (K) Fg. 15 Tme vaatns n P n, P ut, T n, T ut, T s, q and u f u 0=13.6 m/s, q 0=16.51 MW/m and = m/s at P ut0= kpa and T sub,n0=156.3 K 37

39 Sldeed t cppe electde plate Axal velcty Heated length Sldeed t cppe electde plate Axal velcty THD-F19 THD-F194 Fg. 16 Typcal phtgaph f SUS304 test tubes f d=6 mm and L=59.7 mm buned ut n flw tansent CHF expements 38

40 u c (m/s) u 0 +0 % -0 % +5 % -10 % Flw Tansent Data SUS304 Tube d=6 mm 30 L= mm L/d= P n = kpa T sub,n =150 K (q c,sub,st ) u=4m/s 0 q c,sub =q 0 u=4 m/s u 0 (m/s) Eq. (3) u c Eq. (4) q 0 Eq. (5) (m/s ) 10 0 q c,sub (W/m ) Fg. 17 Relatnshp between u c and and that between q c,sub and wth u 0=6.9, 9.9 and 13.3 m/s at q 0=(q c,sub,st) u=4m/s W/m f P ut=800 kpa and T n=90.1 t K 39

41 u c /u c,st, q c,sub /q c,sub,st u 0 +5 % -5 % Flw Tansent Data SUS304 Tube d=6 mm L= mm L/d= P n = kpa T sub,n =150 K u 0 (m/s) u c /u c,st q c,sub /q c,sub,st +10 % -10 % Eqs.(6) & (7) Eqs.(8) & (9) (m/s ) Fg. 18 Relatnshp between u c/u c,sub,st and and that between q c/q c,sub,st and wth u 0=6.9, 9.9 and 13.3 m/s at q 0=(q c,sub,st) u=4m/s W/m f P ut=800 kpa and T n=90.1 t K 40

42 Sldeed t cppe electde plate Tace f the vap patch Sldeed t cppe electde plate Taces f the vap patch Heated length Heated length Sldeed t cppe electde plate Sldeed t cppe electde plate Flw velcty Flw velcty (a) (b) Fg. 19 Typcal phtgaph f the used test tubes wth (a) d=9 mm and L=48 mm [], and (b) d=6 mm and L=59.5 mm [31, 3] buned ut due t the hyddynamc nstablty 41