PREDICTION OF FOULING THICKNESS AND BULK MILK OUTLET TEMPERATURE BY ARTIFICIAL NEURAL NETWORK (ANN) MODELING IN HELICAL TRIPLE TUBE MILK STERILIZERS

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1 Pceeding Intenatinal Cneence n Heat Exchange Fuling and Cleaning VIII (Pee-eviewed) June 4-9, 009, Schladng, Autia Edit: H. Mülle-Steinhagen, M.R. Malayei and A.P. Watkinn PREDICTION OF FOULING THICKNESS AND BULK MILK OUTLET TEMPERATURE BY ARTIFICIAL NEURAL NETWORK (ANN) MODELING IN HELICAL TRIPLE TUBE MILK STERILIZERS A. Chatuved S. Achaya and A. K. Datta Agicultual and Fd Engineeing Depatment Indian Intitute Technlgy Khaagpu Wet Bengal 7 30, India akd@age.iitkgp.enet.in ABSTRACT An ANN mdel i implemented n helical tiple tube UHT lk teilize and eult ae validated with the actual meaued data. The cale-up tategy ued hee i ucceul in pedicting the eult the the heat exchange. The neual netwk develped i pedicting data accuately with t mean quae e (RMSE) in de 0-4. It i und that the epne utlet tempeatue, the eect Reynld numbe i the highet, whee a uling laye thickne the eect time i the maximum. The uling thickne educe a the diamete inceae; thi may be due t the inceae in uace aea heat tane with the inceae in diamete and length. Thi mdel can be vey ueul pedicting the lng-tem behaviu tubula UHT lk teilize ued in indutie. INTRODUCTION Milk uling ha becme a pblem geat pactical igniicance a a a plant anitatin i cncened. A me imptant eect i the pible litatin the time which a heat teatment plant can be peated withut intemediate cleaning. The peating time may be eticted eithe thugh the depit btucting the lw paage in the heat exchange, cauing exceive peue dp thugh eductin the heat tane ceicient heating uace (lk depit ae invaiably p themal cnduct), making it inceaingly diicult t maintain the equied pceing tempeatue. Beide qualitative le the d, pduct cbial aety i nt guaanteed. Depit matin thu inceae the enegy ct the plant, and theee t impve the peating eiciency and t enue pduct aety, equent cleaning i neceay, which i ecncally undeiable a it educe the availability expenive plant and inceae the pceing ct. Al the pblem depit matin maniet itel ecncally thugh the time and mateial equied t clean the lid uace and thugh l pduct and le neal and the nutient in the depit laye. The additinal annual ct in the daiy induty caued by uling ae etimated at 60 llin Eu in Eupe (nkmann, 986) and in USA luid lk induty (pateuized lk pductin, i.e. n teilized and ulta high tempeatue lk) at $40 llin pe yea, appximately at cuent pice (Sandu and Singh, 99). Tw decade ealie, the ttal uling ct in the U.S. indutie wa etimated t be $ llin pe yea (Rebell et al.988). It wa al epted that uling caue a deceae in the eiciency heat exchange by 0 t 80% at an aveage 6%. Cattel (98) epted that the pblem uling ha been eiu that the plate heat exchange cannt be un me than ive hu cntinuuly due t the litatin peue imped n the ubbe gaket. Ranjan and Datta (999) and Sah et al. (005) imulated the uling behaviu a a unctin time and pitin within the duble cncentic tube heat exchange. Hyddynac and heat balance ae ued t mulate tw independent dieential equatin expeing bulk lk tempeatue and uling thickne a unctin time and pitin. The imptant bevatin wa und that the uling thickne tabilized ate 0.7h. Tyda et al. (994) pped the applicatin uling mdel t bth heating and cling ituatin. In the heating ituatin it wa hwn that the expeimental depit pile culd be matched eanably well by aung eithe the denatued (unlded) ptein, aggegated ptein bth epaately a the nly ulant. In the cling ectin, hweve, the iginal mdel did nt pduce bviu decaying pile. Even with the incpatin the eveible tep the ptein denatuatin, the mdel did nt pduce what wa ten witneed in the acty. Thi indicate that the depitin ate cntant mut be a tempeatue dependent vaiable, which educe t, a the wall tempeatue appache t a value whee thee i viibly n uling n the uace. Expeimental data wee btained by Schaml et al. (996) and ued t mdel the ate depit matin a a unctin time. A me cmplex mdel incpating the tempeatue dieence between the bulk luid and bunday laye the luid, the ptein chety, ma tane and wall eactin i epted by Scheie and Fye (995) detenatin the depit ma gwth ate. A numeical pcedue baed n the methd chaacteitic wa peented by Fye and Slate (985). F the imulatin the aveage veall heat tane behaviu a heat exchange, which i ubjected t checal eactin uling, the cntitutive heat exchange equatin wee diectly integated tgethe with an equatin that decibed the lcal uling ate at a pint n the heat tane uace. The pcedue wa 3

2 Chatuvedi et al. / Pedictin Fuling Thickne... demntated uling tubula heat exchange by kimmed lk emplying an expeimentally detened lcal uling ate mdel. A pemance calculatin u dieent exchange wa peented t illutate apect uling behaviu. Jun and Pui (005) have peented a cnideable amunt wk n mdeling the uling pce a well a the hyddynac and themdynac pemance heat exchange. They have ummaized the available inmatin n exiting uling mdel in tem uling mechanim, dynac pemance heat exchange and integated uling dynac. Summaizing thee appache, it i bviu that nly ew them cnideed the cmpitin the pduct, in additin t that, mt mdel ae nly develped pateuizatin cnditin. Hence the eect at UHT tempeatue ae nt taken int accunt. Agan and Cavelh(996) deigned a knwledge baed expet ytem aement uling in heat exchange. The uling laye thickne wa pedicted n the bai educed eectivene. The eectivene wa meaued in tem NTU. Heat exchange dimenin and ht and cld luid lw ate at dieent peating cnditin wee taken a input the uling laye thickne pedictin. Zhu and Zhang (003) devied a methd nline meauement uling laye thickne in bewey wt evapat uing a t ening appach. The act aecting uling wee tempeatue, ph, tubidity and vicity the wt, tempeatue heating vap, lw ate heating vap and peue in evapat. Cnideing all the abve pint llwing bjective wee taken up (i) t tain ANN uing data available m a labaty mdel lk teilize; (ii) t ptie the netwk achitectue nimum deviatin in pedicted eult; (iii) t pedict the elative imptance independent vaiable n utlet tempeatue and uling laye thickne in helical tiple tube heat exchange; (iv) T apply ANN t pedict uling thickne and maximum tempeatue in helical tiple tube heat exchange peatinal in induty. THEORETICAL PRINCIPLES In helical tiple tube heat exchange (HTTHE), the team lw in the innemt and the utemt tube and pce luid lw in annula ptin the ddle tube. In heat tane calculatin the baic aumptin i that heat lt by team in heating ectin i ued t inceae the tempeatue pce luid in the ame ectin. The dieent mde heat tane ac the heat exchange unde ideal cnditin (i.e. nn uling) ae a llw (i) cnvectin heat tane due t team cndening n utide uace the ddle tube and inide uace the innemt tube; (ii) cnductin ac the ddle tube wall t the inide uace the ddle tube and ac the inne tube wall t utide uace the inne tube; (iii) cnductin thugh the uled laye depited n the inide utide uace() the ddle tube; (iv) Cnvectin heat tane thugh the ute wall the inne tube and the inne wall the ddle tube. The veall heat tane i calculated taking the abve mde heat tane int accunt. When luid lw in annula egin tube, the luid ide cnvectin heat tane ceicient can be calculated unde tubulent lw cnditin by the llwing equatin: 0.53 k D Di eq h 0.07 N N 3. 5 () Re P Deq D D c Peue dp in the annulu can be detened m () (4): P P a P () L v P 4 (3) a c D eq D eq P v (4) Dc Fictin act can be calculated by the llwing expein: D eq c 0. (5) N Dc Re lg0 7 The enthalpy balance in the annulu a tiple tube i given by: A v C T t p T A v C T xt U p A T T t U A T T t i i x T A C xt p t (6) Uing chaacteitic technique a decibed by Aciv (956), equatin (6), a patial dieential equatin can be cnveted t dinay dieential equatin. The dinay dieential m equatin (6) i: dt U h U T T i i (7) i h C i p U h U i m i whee, i i (8) and, h h d i (9) i m h h d m F develping the mdel uling in helical tiple tube UHT lk teilize, a mdel a uggeted by Fye and Slate (985) tubula heat exchange wa ued with uitable mdiicatin. The baic equatin ued depitin ate and deciptin the mdiicatin made in the aeaid mdel, ae a llw: h 3

3 Heat Exchange Fuling and Cleaning VIII 009 d and, d whee, E R Td i k exp k di i (0) E m k exp k d m () R Td d h ln () and kd Fuling thickne d i i d m i h i ln d k d (3) Baed n the pinciple heat lux equivalence cncept T d i ubtituted in equatin (0), then the lcal veall ate lid accumulatin n ute uace inne tube can be epeented a: d Ei kdi exp R i T 73 T 73 i ki (4) Silaly, the lcal veall ate lid accumulatin n the inne uace ddle tube can be epeented a given belw: m m dm E i k exp k d m R T 73 T 73 m m i (5) Numeical lutin T, and m a unctin pitin (x) and time (t) wee btained by electing the numbe nde N alng -chaacteitic. The tempal epaatin the nde alng - chaacteitic wa thu et (Ranjan and Datta, 999) a: L. (6) N v Initial cnditin wee et a, ( 0)=0, i=,,3, N m ( 0)=0, i=,,3, N T (0, =T in, j=,,3, Tube ide luid tempeatue T ( and uling thickne n the ute wall the inne tube and the inne wall the ddle tube wee btained. Integatin equatin (7), (4) and (5) uing Mdiied Eule technique give: dt T ( i /, T (7) j ) dm m( j / ) m( (8) d j / ) (9) dt T ( i, T (0) ( i /, dm m( j ) m( () j ) j / ) d j ) () j / ) The abve numeical cheme wa applied n an HTTHE having inne tube 8.5 mm utide diamete, ddle tube.7 mm inide diamete and 300 mm cil diamete. T, m and wee btained a unctin time and pitin. Thi eult wa ued a the taining mdel the ANN. Uing tan igmid tane unctin and multilaye eed wad netwk wa identiied with the utput the numeical cheme decibed abve. Once the netwk achitectue wa inalized the uling thickne and lk utlet tempeatue wee btained the llwing heat exchange: Table. Gemetic cniguatin heat exchange ued pedictin uling thickne and bulk lk utlet tempeatue. Outide diamete inne tube, mm Inide diamete ddle tube, mm Cil diamete, mm The even input t the ANN wee Reynld Numbe, Panl Numbe, utide diamete inne tube, inide diamete ddle tube, cil diamete, peue dp and HTTHE length. RESULTS Expeiment wa cnducted uing the mallet heat exchange lited in Table with kim lk having at cntent 0.5 % and peating unde inlet and utlet tempeatue 95 and 45 C with team at 60 C a the heating agent. The ANN taining wa caied ut with the peue dp data btained in the mentined heat exchange unning with a kim lk lw ate 30 l h -. The accuacy the mathematical mdel had been etablihed in Nema and Datta (006). The ame wa ued validating the Neual Netwk taining eult. Table peent the eult tial vaiu ANN achitectue t indicate that the 9 th tial the nmalized RMSE value eache the nimum 7.6 x

4 Chatuvedi et al. / Pedictin Fuling Thickne... Table. Rt mean quae e (RMSE) a unctin ANN achitectue. N. N. laye Input laye neun t hidden Laye neun nd Hidden Laye neun Output Laye neun RMSE X Table 3. Cnnecting weight vaiu input (x). time, N Re, 3 N Nu, 4 d i, 5 d, 6 length, 7 peue dp. Input Laye Hidden Laye Hidden Laye x Figue. Helical tiple tube heat exchange ued uling tudy. Depit thickne (x 0.000m) Depit Thickne v. Time Time (n) Seie Seie Seie3 Seie4 Seie5 Figue. Fuling depit thickne in mm a unctin time peatin (Seie i the mallet HTTHE). Figue, 3 and 4 peent uling thickne, utlet tempeatue and peue dp in vaiu HTTHE duing the it 7 nute peatin. Tempeatue (Celciu) Bulk lk utlet tempeatue v. time Time (n) Seie Seie Seie3 Seie4 Seie5 Figue 3. Milk utlet tempeatue in C a unctin time (Seie i the HTTHE mallet dimenin). 34

5 Heat Exchange Fuling and Cleaning VIII 009 Peue dp (kpa) Peue dp v. time Time (n) Seie Seie Seie3 Seie4 Seie5 Figue 4. Peue dp in kpa a unctin time (Seie i the mallet HTTHE). DISCUSSION A evident m the eult, the ANN achitectue input laye llwed by 4 it hidden laye bee 3 ecnd hidden laye t give utput laye pvide the leat deviatin m the tial cmputed input. The igue ugget that uling i the mt evee in the mallet HTTHE. Thi act i well demntated by the thee igue with educed depit thickne, malle utlet tempeatue deviatin m et pint and lw peue dp. CONCLUSIONS The ANN mdeling eulted in a bette phyical undetanding the uling mechanim in the lk teilize. The eult the mdel jutiy bigge HTTHE lk teilizatin a it can handle lage quantity lk with educed peatinal diiculty (Figue, 3 and 4). The uling ccuing in the lage heat exchange can be vecme with ppe cntl actin team peue elevatin t maintain a eanable duatin peatin pi t cleaning the heat exchange. NOMENCLATURE A Aea lw wking luid, m A i A m C p C w d D c D eq D i D Heat tane uace aea baed n inide diamete ddle tube, m Heat tane uace aea baed n utide diamete the innemt tube, m Mdiied t numbe n the ute uace the innemt tube, dimeninle Mdiied t numbe n the inne uace ddle tube, dimeninle Speciic heat wking luid, J/kg K Speciic heat wate, J/kg K Chaacteitic dimenin, m Cil diamete, m Equivalent diamete tube, m Inne diamete ddle tube, m Oute diamete the innemt tube, m E i E c ( ) ( m ) h h i j k d k di k d k k i k L N N P N Re R d d i i t T d T d T T Activatin enegy n the ute uace the innemt tube, kj/kg ml Activatin enegy n the inne uace ddle tube, kj/kg ml Fictin act, dimeninle Functin Functin m Film heat tane ceicient with uled laye peent, W/m -K Film heat tane ceicient withut uling, W/m -K Index Index Themal cnductivity uled laye, W/m-K Depitin ate cntant due t the ute uace the innemt tube, l/ Depitin ate cntant due t the inne uace ddle tube, l/ Themal cnductivity lk, W/m-K Remval ate cntant due t the ute uace the innemt tube, l/ Remval ate cntant due t the inne uace ddle tube, l/ Length tube, m Numbe nde Panl numbe, dimeninle Reynld numbe, dimeninle Univeal ga cntant, 8.34 kj/ kg ml K Radiu up t uled laye due t the ute uace the innemt tube, m Radiu up t uled laye due t the inne uace ddle tube, m Inne adiu the innemt tube in HTTHE, m Inne adiu ddle tube in HTTHE, m Oute adiu the innemt tube in HTTHE, m Oute adiu ddle tube in HTTHE, m Time, Tempeatue at the inteace uling depit and pce luid n the ute uace innemt tube, C Tempeatue at the inteace uling depit and pce luid n the inne uace ddle tube, C Pce luid tempeatue, C Tempeatue team, C 35

6 Chatuvedi et al. / Pedictin Fuling Thickne... U i Ui U U v P P a P t x m Oveall heat tane ceicient due t the inne uace ddle tube in heating ectin with uling, W/m -K Oveall heat tane ceicient due t the inne uace ddle tube in heating ectin withut uling, W/m -K Oveall heat tane ceicient due t the ute uace the innemt tube in heating ectin with uling, W/m -K Oveall heat tane ceicient due t the ute uace the innemt tube in heating ectin withut uling, W/m -K Aveage velcity pce luid, m/ Thickne uling laye, m Time inteval, Peue dp, Pa Axial peue dp, Pa Radial peue dp, Pa Finite time inteval, Finite length element, m Film ceicient and themal cnductivity ati the ute uace the innemt tube, dimeninle Film ceicient and themal cnductivity ati the inne uace the ddle tube, dimeninle Denity pce luid at mean tempeatue, kg/m 3 S. Jun and V. M. Pu 005, Fuling mdel heat exchange in daiy pceing: a eview, Junal Fd Pce Engineeing, 8, pp. 34. P. K. Nema and A. K. Datta, 006, Impved lk uling imulatin in a helical tiple tube heat exchange. Intenatinal Junal Heat and Ma Tane, 49, pp R. Ranjan, and A. K. Datta, 999, Milk uling imulatin in tubula heat exchange. Pceeding 6th Natinal Cneence n Fluid Mechanic and Fluid Pwe, IIT Khaagpu, pp W. J. Rebell, S. L. Richlen and F. Chilh, 988, The Ct Heat Exchange Fuling in the US Indutie, Rept N. EGG-M Depatment Enegy, Wahingtn, DC. P. K. Sah, I. A. Anai and A. K. Datta, 005, Milk uling imulatin in helical tiple tube heat exchange, Junal Fd Engineeing, 69, pp J. E. Schaml, T. Spiegel and H. G. Kele, 996, Eect cmpitin and cncentatin daiy liquid n uling tuctue. Milchwienchat, 5(), pp I. Tyda, P. J. R. Scheie and P. J. Fye, 994, A cmputatinal mdel eactin uling m whey ptein lutin. In Fuling and cleaning in d pceing, Jeu Cllege, Cambidge, Mach 3-5, pp. 9. REFERENCES A. Aciv, 956, Methd chaacteitic technique applicatin t heat and ma tane pblem. Indutial and Engineeing Chety, 48, pp N. H. Agan and M. G. Cavalh, 996, Knwledge baed expet ytem uling aement indutial heat exchange. Applied Themal Engineeing, 6, pp D. W. nkmann, 986, Enegie-en-lieuapecten van het einigen van vewekingappaatuu. In G. J. M. Wlbe et. al. (Ed.) Milieuapecten van de beeiding vn vedingddelen (Envinmental apect d manuactue), NIZO Mdeling M0, pp. 6-76, NIZO, Ede. G. S. Cattel, 98, Liquid lk develpment in heat teatment plant. Junal Daiy Reeach, 5, pp P. J. Fye and N. K. H. Slate, 985, A diect imulatin pcedue checal eactin uling in heat exchange, The Checal Engineeing Junal, 3, pp