EFFECT THE FORM OF PERFORATION ON THE HEAT TRANSFER IN THE PERFORATED FINS

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1 ISSN-L: , ISSN: Vol. 4 No. 3 Ma 2013 Aademi Researh International EFFECT THE FORM OF PERFORATION ON THE HEAT TRANSFER IN THE PERFORATED FINS Raaid R. Jassem Department o Mehanial Engineering, College o Engineering, Tikrit Universit, IRAQ. raaid.rashad@ahoo.om ABSTRACT Etended surae heat ehangers are eas in onstrution and etensivel use in man o the industries. Continuous researh is going on to improve its eetiveness b reduing the thermal boundar laer thikness and inreasing the heat transer surae area. Perorations in the ins one wa that used to improve its eetiveness. An eperimental stud submitted to investigate the heat transer b natural onvetion in a retangular perorated in plates. Five ins used in this work irst in non-perorated and others ins perorated b dierent shapes these ins peroration b dierent shapes (irle, square, triangle, and heagon) but these perorations have the same ross setion area(113 mm 2. These perorations distributed on 3 olumns and 6 rows. Eperiments produed through in an eperimental ailit that was speiiall design and onstruted or this purpose. The results show that the drop in the temperature o the non-perorated in rom 72 to 57 o C while the temperature drop in perorated ins, at the same power supplied (126 W) was (72-52 o C), ( o C), (72-50 o C) and (72-48 o C) or shapes (heagonal, square, irular and triangular) respetivel Figure(9). The largest value o RAF at triangular peroration and the smaller value ourred in irular peroration. Also, triangular peroration gives best values o heat transer oeiient and then the irular, square, heagonal, and non-peroration respetivel. Kewords: Heat transer, Surae heat ehangers, Perorated in plates INTRODUCTION The removal o eessive heat rom sstem omponents is essential to avoid the damaging eets o burning or overheating. Thereore, the enhanement o heat transer is an import subjet o thermal engineering. The heat transer rom suraes ma in general be enhaned b inreasing the heat transer oeiient between a surae and its surroundings, b inreasing the heat transer area o the surae, or b both. In most ases, the area o heat transer inreased b utilizing etended suraes in the orm o ins attahed to walls and suraes [1]. Etended suraes (ins) requentl used in heat ehanging devies or the purpose o inreasing the heat transer between a primar surae and the surrounding luid. Dierent tpes o in heat ehangers, ranging rom relativel simple shapes, suh as retangular, square, lindrial, annular, Tapered, or pin ins, to a ombination o dierent geometries that applied heat ehanger [2]. One o the primaries aimed in the design o modern thermal sstems is the ahievement o more ompat and eiient heat ehangers. Reduing energ loss due to ineetive use and enhanement o energ transer in the orm o heat has beome an inreasingl important dut or the design engineers o thermal sstems, onsidering the world wide inrease in energ demand. This dut requires emploing heat transer suraes with high heat transer oeiients and high area 198 Copright 2013 SAVAP International

2 Part-I: Natural and Applied Sienes ISSN-L: , ISSN: Vol. 4 No. 3 Ma 2013 ompatness. A partiular attention is required in surae area design when use the gas in heat ehangers [3]. Fins as heat transer enhanement devies have been quite ommon. As the etended surae tehnolog ontinues to grow, new design ideas emerge, inluding ins made o anisotropi omposites, porous media, and perorated and interrupted plates [4]. The requirements o lightweight ins and eonomial, so the optimization o in size is ver important in in's design. Thereore, ins must be designed to ahieve maimum heat removal with minimum material ependiture, taking into aount, however, the ease o manuaturing o the in shape [5]. Large number o studies has been onduted on optimizing in shapes. Other studies have introdued shape modiiations b utting some material rom ins to make avities, holes, slots, grooves, or hannels through the in bod to inrease the heat transer area and/or the heat transer oeiient [6]. One popular heat transer augmentation tehnique involves the use o rough or interrupted suraes o dierent onigurations. The surae roughness or interruption aims at promoting surae turbulene that is intended mainl to inrease the heat transer oeiient rather than the surae area [7]. It was reported that non-lat suraes have ree onvetion oeiients that are 50% to 100% more than those o lat suraes [8]. Several other researhers reported a similar trend or interrupted, perorated, and serrated suraes, attributing the improvement to the restarting o the thermal boundar laer ater eah interruption, indiating that the inrease in onvetion oeiient is even more than enough to oset lost area [7]. In 2007 A. M. &, the other [9]. Treats the natural onvetion heat transer rom perorated ins. The temperature distribution was eamined or an arra o retangular ins (15 ins) with uniorm ross-setional area ( mm) embedded with dierent vertial bod perorations that etend through the in thikness. The patterns o perorations inlude 18 irular perorations (holes). Eperiments were arried out in an eperimental ailit that was speiiall design and onstruted or this purpose. The heat transer rate and the oeiient o heat transer inreases with peroration diameter inreased. Abdullah H. AlEssa, Aman M. Maqableh and Shatha Ammourah [10] were enhanement o natural onvetion heat transer rom a horizontal retangular in embedded with retangular perorations o aspet ratio o two. The results o perorated in ompared with its equivalent solid one. An eperimental stud was arried out or geometrial dimensions o the in and the perorations. The stud investigated the gain in in area and o heat transer oeiients due to perorations. The onluded that, values o retangular peroration dimension, the perorated in enhanes heat transer. The magnitude o enhanement is proportional to the in thikness and its thermal ondutivit M.R. Shaeri, M. Yaghoubi, K. Jaarpur [11] stud the turbulent luid low and onvetion heat transer around an arra o retangular solid with dierent number o peroration and dierent size. Eperiments were onduted or the range o Renolds no. rom 2000 to 5000 based on in thikness and pr= This Stud is aimed mainl at eamining the etent transer enhanement rom vertial retangular ins under natural onvetion. Conditions as a result o introduing bod modiiation (perorations) to the in bod. The modiiation in this work is irular, square, triangular, and heagonal perorations made through the in thikness. The stud investigates the inluene o perorations on heat transer rate or heat dissipation rate o the perorated in. The modiied ins (perorated ins) are ompared to the orresponding solid (Non perorated) in in terms o heat transer rate, also omparing will be between all ins. Copright 2013 SAVAP International 199

3 ISSN-L: , ISSN: Vol. 4 No. 3 Ma 2013 Aademi Researh International MATHEMATICAL ANALYSIS OF FIN PERFORATED Perorated ins an be used to inrease the heat transer oeiient and eetive heat transer area. The hange in magnitude o the surae area depends on the geometr o the perorations (Abdullah and Mohammed, 2009)[12]. In this paper, the number o perorations (N ) in the - diretion (L) and (N ) in the - diretion (W) an be assumed. Also the dimensions o in are known. The peroration ross setional area (A) ma be assumed, and then the dimension o an peroration an be alulated. The surae area o the uniorm longitudinal retangular perorated in an be epressed as: A = A + A + N p p ps t A p ( 2 W. L 2N. A ) + ( Wt. ) + ( N A ) A =. p C ( A A ) A A + N 2 =. (1) p Equation (1) an be written as: p ( A A ) A A + N. N 2 =. (2) p In order to ompare the heat transer surae area o the perorated in (A p ) to that o the onventional one (A ), the in surae area ratio RAF is introdued and is given b: A RAF = A p ( A 2A ) N N p RAF = 1+. (3) A The material volume o the perorated in is ompared with the volume o non- perorated in b volume redution ratio whih given b: V RVF = V p = ( LW.. t N N A t) LW.. t N. N. A RVF = 1. (4) LW. Similarl, perorated in has less weight than that o equivalent non- perorated one. This aspet epressed b the in weight redution ratio RWF deined as ollows: W RWF = W p = ( W N. N. A. t.ρ) W ( N. N. A. t. ρ) N. N. A RWF = 1 = 1.. (5) LW.. t. ρ LW. Aording to the peroration shape and dimension that an be ut out rom the in bod, in with the irular peroration pattern is studied. The number o peroration in a longitudinal diretion (N ), in the transverse diretion (N ), and the peroration diameter is (b). The diretional perorations spaing S and S : ( N ) S L = N. b Copright 2013 SAVAP International

4 Part-I: Natural and Applied Sienes ISSN-L: , ISSN: Vol. 4 No. 3 Ma 2013 L N. b S =. (6) N + 1 ( N ) S W = N. b+ + 1 W N. b S =. (7) N + 1 The heat transer surae area o the in an be epressed as: A = A 2 N. A + N. A p ( A A ) b Ap = A + N p 2 = A + NC. b t 2 The ratio RAF and RVF an be epressed as: π. b. N. N RAF = 1+ And ( 2W. L + Wt) p b t 2 π 2 N. N b RVF = 1 4. (10) LW π. (8). (9) ANALYSIS OF HEAT TRANSFER COEFFICIENT An eperimental orrelation to estimate the onvetion heat transer oeiient o the arra o vertial oriented parallel lat plate given b (Simmons, 2002)[13 ] Nu Where. 35 h B Ra 0.75 = = (1 e Ra )... (11) k 24 B is the average spae between adjaent ins. 2 4 ρ. g. β. C p. B. T Ra =. (12) µ. k. L Several studies (12, 13) reported that, the surae heat transer oeiient o perorated suraes is a untion o open area ratio [ROA] o the perorated surae. The open area ratio deined as: OA ROA=. (13) OA ma Where OA is the atual open area OA = A. N. N (14) = A. N OA ma is the maimum possible perorations open area, whih is deined as: Copright 2013 SAVAP International 201

5 ISSN-L: , ISSN: Vol. 4 No. 3 Ma 2013 Aademi Researh International OA = ma A. N,ma A. N,ma. N,ma =... (15) Where N, ma and N, ma, are the maimum possible number o the perorations. These numbers related with the peroration spaing equal zero. The perorated surae heat transer oeiient ratio an be epressed as Kakaae [14]: OA R h = (16) OA ma The ilm heat transer oeiient o the perorated surae (h ps ) is epressed as: OA h ps = ( ) h. (17) OA ma EXPERIMENTAL WORK The eperiments were arried out in an eperimental ailit that was speiiall designed and onstruted or this purpose. Figure 1 shows draw o the Shemati drawing or the apparatus. The eperimental setup inludes a heat sink supplied with heating elements and data aquisition sstem. The heat is generated within the heat sink b means o one heating element power o 670 W. All the eperimental data are reorded b the data aquisition sstem. The heat sink hosen or eperiments is aluminum linder o 50.8 mm diameter and 270 mm length. One hole was drilled in the linder in whih one heating element was pressed. The power supplied b the heating element was 670 W. Five aluminum straight ins were itted radiall Figure (2). The ins are 100 mm long, 270 mm wide and 2 mm thik. These ins were divided into ive groups as Table 1. Case Perorated Shape Table 1. Fins used in researh shown in ollowing Figure (2). Cross Setion Area o Peroration (mm 2 ) Number o Peroration in eah in 1 Non-perorated Cirle (3*6) 3 retangle (3*6) 4 triangle (3*6) 5 Heagonal (3*6) A variable transormer o tpe 50B with input 220 V and Hz and output V, 20 A and 7.5 kva were used to regulate the voltage supplied to the heating elements (Figure 1). The eperimental data measured b twent seven alibrated thermoouples o tpe-k, to measure the temperature at dierent loations o ins.. One thermoouple ied on the outside diameter o the aluminum linder in order to measure the base temperature o the in. One thermoouple is used to measure air temperature. Twent ive o thermoouples were divided into ive ins equall. Eah thermoouple was ied to the surae o the test in at equal spae (20 mm) loations along the in length. The apparatus was allowed to run or about 60 minute, until the stead state was ahieved. The reording o temperature was begun ater stead state had been reahed. 202 Copright 2013 SAVAP International

6 Part-I: Natural and Applied Sienes ISSN-L: , ISSN: Vol. 4 No. 3 Ma 2013 Figure 1. Shemati drawing or the apparatus and devies used 3-Square-peroration 1- Non perorated in 4-Triangular -peroration 5- Heagonal -peroration 2- Cirular-peroration RESULTS AND DISCUSSION Figure 2. Fins used in apparatus In this eperimental work was ondut to investigate the peroration shape geometr eet on the onvetion heat transer rom the ins b Natural Convetion. Were the stud will be ompared between dierent shapes o perorations and then with non-perorated in. The temperature distribution along the in is one o the ators that relet the perormane o the ins, whih it an be used to ompare between dierent ins. The results show that, the highest temperatures were along the non-perorated in, and lower temperatures distribution along the peroration ins was along the peroration in with triangular shape. Then the in with a irular shape. These results are shown in Figure (3) or dierent values o the supplied power. Also, the dierene between temperature in the base o in and its tip regarded rom the important ators in the pereption o the work o the in, whih it an be used to ompare this ator with other ins. and through the same graphis in Figure (3) an be sa that, the highest drop o temperature between the in's base and it is tip an event in the triangular in holes. This happen beause the triangle area destroed the area o thermal boundar laer larger than the rest shapes beause its width larger than rest shapes. Copright 2013 SAVAP International 203

7 ISSN-L: , ISSN: Vol. 4 No. 3 Ma 2013 Aademi Researh International Non perorated Traingular P. Heagonal P. Cirular P Non perorat Traingular P. Heagonal P. Cirular P. (a)16 W (b)26 W ()45 W Non per Traingula Square P Heagona Cirular P Non pero Traingular Heagona Cirular P Non per Traingula Square P Heagon Cirular P Non perora Traingular P Heagonal P Cirular P (d)51 W (e)126 W ()186 W Non perorated Traingular P. Heagonal P. Cirular P. Non perorated Traingular P. Figure 3. The Temperature Distribution along ins Peroration shape, eets on the heat transer surae area o the ins, whih it one o the important ators on the in's perormane. Figure (4) shows the values o RAF with peroration shape. The results appear that the highest value o (RAF) at in o triangular peroration while the lowest value o (RAF) at in with irular perorations Despite the lak o dierene between them. Heagonal P. Cirular P. (g)204 W (h)304 W (i)386 W Non perorated Traingular P. Heagonal P. Cirular P. 204 Copright 2013 SAVAP International

8 Part-I: Natural and Applied Sienes ISSN-L: , ISSN: Vol. 4 No. 3 Ma RAF irle square heagonal trangle Peroration shape Figure 4. The Relation between RAF and Perorations shape The values o (Rh) appears in igure (5) or eah perorated in, the results show that the maimum value o Rh at triangular perorated ins and the minimum at square perorated ins Rh Rh square irle heagonal trangle ` Peroration shape Figure 5. The Relation Between Rh and Perorations shape The Heat Transer Coeiient regarded one o the main ators on the perormane o ins, whih varies with the peroration shape. From igure, (6) the Heat Transer Coeiient appears with dierent values o supplied energ, or eah peroration shape, where the results show that the highest values o the heat transer oeiients were in the ins with holes triangular shape and then irular. The lower values or the heat transer oeiient were a non-perorated in, and it shows in the results o the orm (6). Copright 2013 SAVAP International 205

9 ISSN-L: , ISSN: Vol. 4 No. 3 Ma 2013 Aademi Researh International Heat Transer Coiient Cirular Retangular Traingular Heagonal Non-perorated Power Suppl CONCLUSION Figure 6. The Relation between Heat Transer Coeiient and Power Supplied The temperature drop along the perorated ins length is onsistentl higher than, that in the non-perorated in. It ontains a larger number o perorations higher than the perorated in that ontained a small number o perorations. The gain in heat dissipation rate or the perorated in is a strong untion o the peroration dimension and lateral spaing. Dereasing the peroration dimension redues the rate o temperature drop along the perorated in. Heat transer oeiient or perorated in that ontained a larger number o perorations higher than the perorated in that ontained a small number o perorations. REFERENCES [1]. Mahmud, A. M. (2005). Perormane o perorated and Non-perorated Fins, Ph.D thesis. Chemial Engineering Dept. Universit o Baghdad. [2]. Sahin, B. & Demir, A. (2008a). Thermal perormane analsis and Optimum Design Parameters o Heat Ehanger Having Perorated Pin Fins. Energ Conversion and Management, 49(6), P [3]. Mohamad, I.. Al-Widan, & Amjad, Al-Shaarawi (2012). Numerial Investigation o Heat Transer Enhanement or a Perorated Fin in Natural Convetion, International Journal o Engineering Researh and Appliations (IJERA), 2(1), pp [4]. Baram, S. & Alparslan D. (2008). Perormane Analsis o a Heat Ehanger Having Perorated Square Fins. Applied Thermal Engineering, 6: [5]. Al-Essa AH, & Al-Hussien, M.S.F. (2004). The Eet O Orientation O Square Perorations On The Heat Transer Enhanement From A Fin Subjeted To Natural Convetion, Heat and mass transer, 40(5): [6]. Elshaei, E.A.M. (2010). Natural Convetion Heat Transer From A Heat Sink With Hollow/Perorated Cirular Pin Fins. Energ, 35: [7]. Kutsher, C.F. (1994). Heat Ehange Eetiveness And Pressure Drop For Air Flow Through Perorated Plates With And Without Crosswind, J.Heat transer, 11(6): Copright 2013 SAVAP International

10 Part-I: Natural and Applied Sienes ISSN-L: , ISSN: Vol. 4 No. 3 Ma 2013 [8]. Chung, B.T.F. & Ier, J.R. (1993). Optimum Design O Longitudinal Retangular Fins And Clindrial Spines With Variable Heat Transer Coeiient. Heat Transer Engineering, 14: [9]. Dr. Aziz, M., Mahmud, T. K., Ibrahim, & Jasim, R. R. (2008).Determination O The Temperature Distribution The Perorated Fins Under Natural Convetion, Tikrit Journal o Eng. Sienes/ 15(2),(63-78). [10]. Abdullah, H., AlEssa, Aman, M., Maqableh, & Shatha, A. (2009). Enhanement O Natural Convetion Heat Transer From A Fin B Retangular Perorations With Aspet Ratio O Two, International Journal o Phsial Sienes, 4(10), pp [11]. Shaeri, M.R., Yaghoubi, M. & Jaarpur, K. (2009). Heat Transer Analsis O Lateral Perorated Fin Heat Sink, Applied energ, 86, [12]. Abdullah, H., AlEssa & Mohammed, Q. Al-Odat. (2009).Enhanement O Natural onvetion Heat Transer From A Fin B Triangular Perorations O Bases Parallel And Toward Its Base, The Arabian Journal or Siene and Engineering, 34(2B). [13]. Simmons, R.E. (2002). Estimation natural onvetion heat transer or arras o vertial parallel lat platter,eletronis ooling. [14]. Kakaae, S. (1989). Heat ehanger thermal hdrauli undamentals. Copright 2013 SAVAP International 207