An Experimental Study of Heat Transfer Enhancement in the Perforated Rectangular Fin

Transcription

1 J Integr Si Tenol, 016, 4(1, 5-9. Artile. Journal o Integrated SCIENCE & TECHNOLOGY An Eperimental Stud o Heat Transer Enanement in te Perorated Retangular Fin Lalta Prasad, * Sonika Tewari, Aswani Kumar Department o Meanial Engineering, G. B. Pant Engineering College, Gurdauri, Pauri Garwal, Uttarakand 46194, India. Reeived on: 5-Sept-015 Aepted on: 11-De-015 Publised on: 19-Jan-016 ABSTRACT Te main objetive o tis stud is to understand te eet o number o perorations on onvetive eat transer eperimentall investigated. Perorations in te ins are one wa tat used to improve its eetiveness. In tis stud, te stead state eat transer rom te solid in and perorated in arras are measured. Te temperature drop along te perorated in lengt is onsistentl iger tan tat or te equivalent non perorated in. Te inlet temperature o te linder ore was in te rage o 353 o C-953 o C or voltage range 100 V to 0 V. Te eat transer depends on te porosit o te in. Heat dissipation rate is inreased in te range o 0% to 70% wit inrease in te number o perorations (4 to 60 up to ertain level. I urter inrease in peroration numbers tis leads to redution o te eat dissipation rom te in. Kewords: Heat transer enanement, Peroration numbers, Natural onvetion, eat transer oeiient, Fin arra INTRODUCTION A growing number o engineering disiplines are onerned wit te energ transitions requiring te rapid eat dissipation rom a surae to surroundings. Te most attrative parameter is to inrease te surae area eposed to te surroundings b te attament o protrusions to te surae in order to inrease te eat transer rate rom te suraes. Te protrusions are alled etended suraes or ins or spines. Te ins serve te purpose o inreasing te eat low area. Some o te use o ins ound in man engineering problems like internal ombustion engines, eat eangers, rerigeration, rogeni proess, nulear uel elements and eletrial apparatus e.g. transormers and motors. 1 Sain and Demir arried out eperimental stud on eat transer and rition ator or eat eanger itted wit square ross setional perorated ins. Te reported tat te use o perorated ins o square ross setion inreases te eat transer rate wi depends on te on te learane ratio and inter-in spaing ratio. Te eperimental Address: Dr. Lalta Prasad Assoiate Proessor, MED, G.B.Pant Engineering College, Pauri Garwal (Uttarakand 46194, India Tel: laltagbpe@gmail.om Cite as: J. Integr. Si. Tenol., 016, 4(1, 5-9. IS Publiations JIST ISSN ttp://pubs.isiene.in/jist analsis o on eat transer enanement and te orresponding pressure drop over a lat surae equipped wit lindrial ross-setional perorated pin ins in a retangular annel. Dumne and Farkade 3 reported te eperimental analsis o on eat transer enanement and pressure drop over a lat surae equipped wit lindrial ross-setional perorated pin ins in a retangular annel. Te use o te lindrial perorated pin ins leads to eat transer enanement as ompared to te solid lindrial ins. Tana 4 reported te stud on eat transer and pressure drop or a retangular annel equipped wit arras o diamondsaped elements. Bot in-line and staggered in arras were onsidered, or values o te longitudinal and transverse spaing. Termal perormane omparisons wit data or a retangular annel witout ins sowed tat te presene o te diamond-saped elements enaned eat transer or equal mass low rate and pumping power. Awasarmol and Pise 5 arried out eperimental stud to quanti and ompare te natural onvetion eat transer enanement o perorated in arra wit dierent peroration diameter and at dierent angles o inlination. Te ound tat te eat transer oeiient was inreased wit perorated ins o 1 mm peroration diameter at te angle o orientation 45, wi sows about 3% enaned eat transer oeiient as opposed to te solid in arra. Saeri and Jen 6 reported te eets o size and number o perorations on laminar eat transer arateristis o an arra o perorated ins at te igest porosit. Te ound tat in a laminar low and at a onstant porosit (Porosit was deined as volume o perorations divided b volume o a solid in, a in wit ewer perorations is more eiient to enane te eat Journal o Integrated Siene and Tenolog J. Integr. Si. Tenol., 016, 4(1, 5-9 5

2 transer rate ompared wit a in wit more perorations. Karabaak and Yakar 7 investigated te eet o oles plaed on perorated inned eat eangers on onvetive eat transer. A perorated inned eater was ompared wit an imperorate inned eater to observe te dierenes in eat transer and pressure drop. Te ound tat te Nusselt numbers or te perorated inned positions were iger tan te Nusselt numbers or te imperorate state. EXPERIMENTAL SETUP AND METHODOLOGY Eperimental onditions In te present work, te seven aluminum straigt ins (105 mm long, 180 mm wide and mm tik were osen. Tere is one non-perorated in and si perorated ins (perorated diameter 10 mm. Te numbers o perorations per in were 4, 3, 36, 44, 55 and 60 teir diameter was 10 mm. Tese ins were itted radiall on an aluminum linder o 60 mm diameter and 10 mm long. One ole was drilled in te linder and one eating element was inserted in te linder as sown eperimental setup in Figure 1.0. Tis aluminum linder is working as eat sink. Te eat is generated witin te eat sink b means o one eating element power o 670 W. Figure 1. Potograpi image o Eperimental set up A variable transormer o tpe P1 wit input 40 V and 50 Hz and output 0-40 V, 0 A and 7.5 kva were used to regulate te voltage supplied to te eating elements. A data aquisition sstem was used to reord te data. K-tpe termoouples were used to measure te temperature at te surae o te test in at equal spaing o 0 mm loated along te lengt o in. Te voltage was varied in te range o 100 V, 140 V, 180 V and 0 V. Te eperimental set up was allowed to run until stead state ondition was aieved ten ater te neessar measurements were reorded. Figure (a sows te design o aluminum linder in te Catia sotware. Te lengt and diameter o te linder was 10 mm and 60 mm respetivel. A ole o size 18 mm was bored in te linder and si numbers o slots (.5 8 mm were ut on te outer surae o te linder. Te linder was assumed to beave as eat sink during eperimental stud. Figure (b sows te design o aluminum plate(fin in te Catia sotware. Te lengt and eigt o te plate was 105 mm and 180 mm respetivel. A ole o size 10 mm was drilledin in te plate. Te number o oles (peroration in te plate were varing rom 4 to 60 to understand te eet o perorations on eat transer rate rom te in. Figure. 3D image o (a aluminum linder (b perorated RESULTS AND DISCUSSIONS Matematial Analsis o Perorated Fin Generall, te eat transer oeiient and eetive eat transer area ould be inreased b using perorated ins and te inrease in eat transer oeiient and surae area depends on te geometr o te perorations. 8 In te present stud, te number o perorations in - diretion and -diretions are N and N respetivel. Te dimension o te in is known in - diretion and - diretions L and W respetivel. Te peroration ross setional area (A is assumed and ten te dimension o an peroration is alulated. Te surae area o te uniorm longitudinal retangular perorated in an be epressed as ollow: Ap A + NC ( Ap A A + N ( Ap A... Eq.(1 In order to ompare te eat transer surae area o te perorated in (Ap to tat o te onventional one (A, te in surae area ratio (SAR is introdued and is given b Eq. (. SAR A p / A [ N 1+ ( A A p A ]... Eq.( Te material volume o te perorated in is ompared wit te volume o non perorated in b volume redution ratio (VRR wi is epressed as Eq. (3: VRR V p / V ( L W t N A t ( L W t ( N A 1... Eq.(3 ( L W Similarl, te perorated in as less weigt tan tat o equivalent non- perorated one. Tis aspet is epressed b te in weigt redution ratio (WRR deined as Eq. (4: Journal o Integrated Siene and Tenolog J. Integr. Si. Tenol., 016, 4(1, 5-9 6

3 W WRR W p ( W ( N 1 N W A t ρ ( L W A t ρ... Eq.(4 Aording to te peroration sape and dimension tat is ut out rom te in bod, te in wit te irular peroration pattern is studied. Te number o peroration in longitudinal diretion N, in te transverse diretion N and te peroration diameter is d. Te diretion peroration spaing S and S: L N d + ( N + 1 S...( Eq.(5 S ( L N d /( N ( Eq.(6 S ( W N d /( N 1...( Eq.(7 + Te eat transer surae area o te in an be epressed as Eq. (8: A p A N A + N Ap A N ( A A A + πn d( t d p /... Eq.(8 Te SAR and VRR an be epressed as Eq. (9 and Eq. (10 respetivel: d [ π b ( t ] SAR 1+ (W L + W t... Eq.(9 [ N ( π / 4 d ] VRR 1 ( L W... Eq.(10 Analsis o Heat Transer Coeiient An eperimental orrelation to estimate te onvetion eat transer oeiient o te arra o vertial oriented parallel lat plate given b Kraus and Bar-Coen 9 as sown in Eq.( Ra 0.75 B Ra(1 e Nu... Eq.(11 K 4 Were: B is te average spae between adjaent ins. ρ g β C p B Ra µ k L 4 T... Eq.(1 Man researers 8,10 ave reported te eat transer oeiient or perorated suraes as a untion o open area ratio (R. Te open area ratio is deined as a ratio o te atual open area to te maimum possible peroration open area as given in Eq. (13. R ma A A, Ma A A, Ma, Ma. Eq.(13 Were N,ma and N,ma are te maimum possible number o te perorations along te in. Tese numbers related wit te peroration spaing equal zero. Te perorated surae eat transer oeiient ratio (R was reported b Kaka et al. 11 as given in Eq.( R 1+ ma Te ilm eat transer oeiient o te perorated surae ( ps is epressed as: 0.75 [1 + ] ps R ma... Eq.(14 Te distane between two ins was alulated b using te Eq. (15: ( D t 6 S π... Eq.(15 6 Were; D is te diameter o te linder and t is te tikness o te ins. Te area o te retangular ins (A 1 L t and te area o te peroration (A n π/4 d were alulated and te ross setional area o te in (A s A 1 -A was alulated to ind te eat transer oeiient as given in Eq. (16 (1.31 k... Eq.(16 S Were; k is te termal ondutivit o te material and S is te distane between two ins. Te value o various parameters were onstant like A 78.54, N, ma 4, N,ma 1 and ma 1369,9. Table 1. Various parameters alulated b using above equations Per. A N N SAR R WRR (no Te various parameters were alulated b using above equations (1-14 and te values are sown in te Table 1. Heat Flow Analsis in Anss Te temperature distribution and eat lu variation analsis was arried out b using ANSYS-14.0 in tis stud. Te temperature distribution and eat lu along te lengt o in at onstant voltage (0V is sown in te Fig. 3 and 4 Journal o Integrated Siene and Tenolog J. Integr. Si. Tenol., 016, 4(1, 5-9 7

4 respetivel. Under stead state ondition, te temperature variation along te lengt o in was in te range o o C as sown in te Figure 3. Wereas te eat lues variation in te in along te lengt is sown in te Fig. 4. Figure 3. Temperature Distribution along te lengt o ins at onstant voltage (0V Figure 4. Heat transer along te lengt o ins at onstant voltage (0V Heat Dissipation at te tip o te perorated in is alulated b using equation 17 as given below: Q in ka (tan( ml + m( t 0 t km a... Eq.(17 {1 + tan( ml} km s Te variation o eat low in te perorated ins is sown in Fig Te various values o dierent parameter are eiter alulated or taken rom te literature like perimeter o in (p 364 mm, mass o in (m 0.39 kg, eat transer oeiient ( 10.0 W/m K and termal ondutivit o Aluminum (k 5 W/m K. Figure 5.0 sows te eet o peroration numbers on te eat dissipation or varing voltage rom volt. It was ound tat te eat dissipation was inreases wit te peroration numbers at varing applied voltages (100-0 V. It as been seen tat maimum eat dissipation (47 W was take plae or peroration 60, or applied voltage o 0 volt; tis is due to iger temperature at te entre o te linder ore as ompared to te oter voltages. Heat dissipated rom in tip (W Peroration No. Figure 5. Eet o Peroration No. on Heat Transer Front te Fin Tip at varing Voltage. Figure 6 sows tat te eet o lengt o te in on te temperature at varing number o perorations. It as been seen rom te igure 6 tat te temperature dereases wit te inrease in te lengt o te in or varing peroration numbers. For a partiular lengt o te in, temperature dereases wit inrease in te number o peroration. Te possible reason or drop in te temperature is lower temperature gradient along te lengt o te in. Temperature ( C Lengt (m Figure 6. Eet o lengt on temperature distribution or varing perorations at onstant voltage (0V CONCLUSIONS 100 Volt 140 Volt 180 Volt 0 Volt 0 peroration 4 peroration 3 peroration 36 peroration 44 peroration 55 peroration 60 peroration Te eat transer analsis on perorated in was arried out in te present stud. Te ollowing onlusions were drawn as given below: Te temperature drop along te perorated in lengt is onsistentl iger tan tat or te equivalent non perorated in. Te gain in eat dissipation rate or te perorated in is a strong untion o te peroration dimension. It was observed tat eat dissipation rate was inreased in te range o 0% to 70% wit inrease in te number o perorations (4 to 60 up to ertain level. I urter inrease in peroration numbers tis leads to redution o te eat dissipation rom te in. Tere are several reasons or derease in eat dissipation rom te in like metal to metal ontat, eat low b ondution and onvetion as well as radiation surae. Te eat dissipation depends on te various parameter like tikness o in, ondutivit o material, lateral Journal o Integrated Siene and Tenolog J. Integr. Si. Tenol., 016, 4(1, 5-9 8

5 spaing, sape o te peroration and temperature o te surrounding. ACKNOWLEDGEMENT Autors are tankul to students (Ankita Nautial, Aswaria Aswal, Haseen and Prema and sta o te Meanial Engineering Department, G. B. Pant Engineering College, Gurdauri, Pauri Garwal, or providing neessar elp during te ourse o te eperimental work. REFERENCES 1 R. Yadav. Heat and mass transer, 5t edition, Central Publiation ouse, Allaabad, India (004. B. Sain, A. Demir. Perormane analsis o a eat eanger aving perorated square ins. Appl. Term. Eng. 008, 8, A.B.Dumne, H.S. Farkade. Heat Transer Analsis o Clindrial Perorated Fins in Staggered Arrangement, Int. J. Innovative Tenol. Eploring Engin. 013, (5, G. Tanda. Heat transer and pressure drop in a retangular annel wit diamond-saped elements. Int. J. Heat Mass Tran. 001, 44(18, U.A. Awasarmol, A.T. Pise. An eperimental investigation o natural onvetion eat transer enanement rom perorated retangular ins arra at dierent inlinations. Ep.Term. Fluid Si.015, 68, M.R. Saeri, T.C. Jen. Te eets o peroration sizes on laminar eat transer arateristis o an arra o perorated ins. Energ. Convers. Manage. 01, 64, R. Karabaak, G. Yakar. Fored onvetion eat transer and pressure drop or a orizontal linder wit vertiall attaed imperorate and perorated irular ins. Energ. Convers. Manage. 011, 5(8-9, A.H. AlEssa, M.Q. Al-Odat. Enanement o natural onvetion eat transer rom a in b triangular perorations o bases parallel and toward its base, Arab. J. Si. Eng. 009, 34(B. 9 A.D. Kraus, A. Bar-Coen. Design and Analsis o Heat Sinks, Jon Wile and Sons, New York, NY, R.R. Jassem. Eet te orm o peroration on te eat transer in te perorated ins. SAVAP International, Part-I: Natural and Applied Sienes, 003, 4(3, S. Kaka, A. Bergles, A. Mainger. Heat eanger termal drauli undamentals. ISBN-10: , Publiser: Springer; 1st edition (1981 Journal o Integrated Siene and Tenolog J. Integr. Si. Tenol., 016, 4(1, 5-9 9