EFFECT OF PERFORATION AREA ON TEMPERATURE DISTRIBUTION OF THE RECTANGULAR FINS UNDER NATURAL CONVECTION

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1 RPN Journal o Engineering and pplied Sienes sian Researh Publishing Network (RPN). ll rights reserved. EFFECT OF PERFORTION RE ON TEMPERTURE DISTRIBUTION OF THE RECTNGULR FINS UNDER NTURL CONVECTION Thamir K. Ibrahim 1, Firdaus Basrawi 1, Marwah Noori Mohammed 2 and Hassan Ibrahim 1 1 Energy Sustainability Fous Group, Faulty o Mehanial Engineering, Universiti Malaysia Pahang, Pekan, Pahang, Malaysia 2 Faulty o Chemial, Natural Resoures Engineering, University Malaysia Pahang, Gambang, Pahang, Malaysia thamir@ump.edu.my BSTRCT In many engineering appliations extended suraes known as ins, are used to enhane onvetive heat transer. The problem o natural onvetion heat transer or perorated ins was investigated in this work. n experimental study was onduted to investigate the natural onvetion heat transer in a in plate with irular perorations. The investigation is onduted to ompare heat transer rate o retangular ins (15 ins) with a size o 100x270 mm embedded with irular vertial shat. The patterns o perorations retangular ins ontain o 18 irular hole. The temperature distribution was examined or an array o retangular ins. Experimental results show that the temperatures distribution along the nonperorated in dereased rom 49 to 42 o C but or the perorated in with hole diameter o 20mm, temperature dereased rom 67 to 47.4 o C with low power (200W). The temperature drop along the non-perorated in dereased rom 170 to 122 o C but the temperature drop or perorated in with hole diameter 20mm dereased rom 170 to o C with high power (900W). lso, when the peroration diameter inreased the derement o the temperature between the base and tip o the in was inreases. Furthermore, when the peroration diameter inreased, the heat transer rate and the oeiient o heat transer also inreased. Keywords: in, natural onvetion, temperature distribution, peroration area. INTRODUCTION heat sink is used to enhane heat transer in many thermal engineering appliations. With the inreasing onerns on eonomi and energy saving onsideration, many researhers attempt develop more eiient heat exhanger. Many types o extended surae are used in pratie as heat transer augmentation surae inluding oset, strip ins, louvered ins, perorated ins and wavy ins (Naik and Probert, 1987; Bayram and lparslan, 2008). The heat transer rom any surae an be enhaned by inreasing the surae area o heat transer, inreasing the oeiient o heat transer between the surae and surroundings, or both. In general, an extended suraes as ins are used to inrease the surae area o heat transer. Whenever a heat exhanger with extended surae is designed, ertain equations or every type o in are required. These equations have all been derived rom the general heat ondution equation where ertain simpliying assumption and boundary onditions are used in eah ase (Naik and Probert, 1987; meel et al., 2013). Walunj at al., 2014, preormed review study on the analysis o natural onvetion heat transer through retangular ins. Various experimental studies were arried out to investigate eet o in height, in spaing, in length and in thikness over onvetive heat transer. n experimental study was arried out by Fujii, (2007), and it was ound that the thermal boundary layer was interrupted by ins. l-essa et al., (2009) were studied the enhanement o natural onvetion heat transer rom a retangular in embedded with equilateral triangular perorations. The results or perorated in were ompared with its equivalent solid one. It was ound that the augmentation in heat dissipation and a redution in weight with used perorations over that o the equivalent solid one. l-doori (2011) arried out an experimental study to enhane the heat transer o ins ontaining irular perorations. The study reported that the temperature drop along the non-perorated in length was onsistently lower than perorated ins. The heat dissipation rate enhanement rom the perorated in was signiiantly aeted by the lateral spaing and size o peroration. Dorigna et al. (2005) perormed an experimental study to determine onvetive heat transer on a multi perorated plate. For a range o perorations spaing they developed an empirial relation or the wide range o a perorated lat plate. Sahin and Demir, (2008) experimentally studied overall heat transer and the eet o various design parameters on heat transer and rition ator or a heat exhanger with square ross setional perorated pin ins in a retangular hannel. The aim o this study was to investigate and analyse the heat transer perormane o uniorm retangular ins used or ooling o eletroni devies in natural onvetion environment with perorations. This study ouses on investigating the eet o inreasing the perorations diameter on the distribution o temperature, the heat transer rate and the oeiient o heat transer. Meanwhile, show eet o inreases the peroration area on the distribution o temperature and the oeiient o heat transer. EXPERIMENTL DETILS The experimental test aility was speially designed and abriated or this purpose. Figure 1 shows the view o the experimental test rig. The experimental setup onsists o heat sink provided by our heating 6371

RPN Journal o Engineering and pplied Sienes 2006-2016 sian Researh Publishing Network (RPN). ll rights reserved. elements with heating apaity o 670 W and data aquisition system.

Four holes were drilled in the ylinder in whih our heating elements were pressed. The power supplied by heating element was 2680 W. Fiteen aluminium straight ins were itted radially.

2 RPN Journal o Engineering and pplied Sienes sian Researh Publishing Network (RPN). ll rights reserved. elements with heating apaity o 670 W and data aquisition system. The heating elements generated the heat inside the heat sink. The heat sink hosen or experiments are aluminium ylinder shat o 100 mm diameter and 270 mm length as shown in Figure-2. Four holes were drilled in the ylinder in whih our heating elements were pressed. The power supplied by heating element was 2680 W. Fiteen aluminium straight ins were itted radially. The ins were 100 mm long, 270 mm wide and 2 mm thik. These ins were divided into ive groups and eah group onsists o three similar pate as shown in Table-1. Table-1. Geometry o various types o in array studied. Figure-2. The design o heat sink. MTHEMTICL NLYSIS OF PERFORTED FIN The study onsidered the omparison o heat dissipation rom the perorated in and the solid one. From view point o view o thermal engineering, thermal systems must be designed and sized to generate, transmit, or dissipate the appropriate amount o heat with the required demand. The optimum operation ondition o thermal system depends on the appliation inluding ooling and heating o ertain omponent. In this study, the number o perorations was N x in the x- diretion (L), N y in the y- diretion (W) and the peroration ross setional area ( ) were assumed. For the uniorm longitudinal retangular perorated in, the surae area an be expressed as ollows: N (1) ps t p 2W. L 2N. W. t N. (2) C p N 2 (3) Figure-1. Experimental setup. variable transormer o type 50B with an input o 220 V and Hz and output o V, 20 and 7.5 kv was used to regulate the voltage supplied to the heating elements as shown in Figure-2. The temperatures were measured by twenty seven K type thermoouples at dierent loations. The heat supplied rom the heat elements ranges during the experiments rom 200W to 900W. To measure base temperature o the ins one thermoouple was ixed on the aluminum shat. In addition, the air temperature was measured by another thermoouple. Twenty ive o thermoouples were divided into ive ins groups equally. Eah thermoouple was ixed to the surae o the test in at equal spae (20 mm) loations along the in length. The apparatus was allowed to run or approximatly 120 minutes, until the steady state was ahieved. The reording o temperature was started ater the steady state had been ahived. Equation (3) an be rearrange and written as equation (4): x y N N 2 (4) p The surae area ratio o the in (RF) deined by equation (5). It represent the ratio between the surae area o onventional in ( ) to surae area o perorated in ( ). RF (5) RF N N 2 x y p 1 (6) Fin weight redution ratio (RWF) an be expressed as Equation. (7), it is ome rom the ratio o the weight perorated in to the weight o solid in: RWF W W N N x y (7) W W t 6372

3 RPN Journal o Engineering and pplied Sienes sian Researh Publishing Network (RPN). ll rights reserved. N x N y t N x N y RWF 1 1 L W t L W The in surae area o heat transer an be alulated by equation (9): 2N. N. (9) p b 2 N. bt N p C (10) 2 The RF an be expressed as equation (11): b b Nx N yt RF 2 1 (11) 2W L W t Equation (12) was used to evaluate the heat transer oeiient by natural onvetion or array o parallel lat plates (Mousa, 2000) h B Ra 1 24 Nu e Ra (12) k where B is the average spae between adjaent ins. 2 4 g C p B T Ra (13) k L Numerous researhers desribed that the oeiient o surae heat transer or the perorated in as a untion o open area ratio (R). The open area ratio o the perorated surae was deined as equation (14) (Sable et al., 2010; l-doori, 2011): R (14) max where is the atual open area x y. N. N. N (15) max is the maximum possible perorations open area, whih is deined as equation (16) max. N,max. N x,max. N y,max (8) (16) RESULTS ND DISCUSIONS In this researh the heat transer by natural onvetion was examined at steady state to show the eet o the geometrial parameters o impressions. Figure-3 shows the temperature distribution along x-diretion o the perorated ins and non-perorated in. s shown in Figure-3, it is obvious that the temperatures along all ins dereased with the x-diretion. It was also ound that when the peroration diameter inreased the temperature drop between the in base and tip inreased too. This was beause the inreasing in the perorated diameter led to derease in thermal resistane o the perorated in. The best heat dissipation appears in the in plate with perorated diameter o 20mm. Meanwhile, when the heat supplied inreased the temperature drop also inreased. The weight redution ratio (RWF) or the perorated in an be alulated by equation (8). Figure-4 shows the relation between the weight redution ratios (RWF) and peroration diameter or the perorated in. It an be noted that the inrease o the peroration diameter led to derease the RWF or the perorated in. Figure-5 shows the eet o the peroration diameter (b) on the in surae area ratio (RF). It is lear that the RF is always smaller than unity. Furthermore, the RF dereased with the inrease o the peroration diameter. It indiates that RF is a weak untion o the in length and width. This is beause the eet o the in tip area whih is smaller as ompared to the in surae area and an be negleted. The heat transer oeiient and in area are the main signiiant parameters on the heat dissipation rate rom the perorated ins. ll ilm heat transer oeiients in this study were assumed to be uniormed and equaled. s shown in Figure-6, the heat transer oeiient ratio Rh was alulated and plotted with eet the peroration diameter. It an be seen that, the heat transer oeiient ratio Rh was always more than 1 and inreased up to the upper limit as the peroration diameter inreased to 20mm. However, the Rh dereased to the lower limit o 1when non-perorated in plate was used. where N x,max and N y,max are the maximum possible number o the perorations along the in. In this study these numbers were assumed to be onstant. Equation (17) was used to estimate the perorated surae heat transer oeiient ratio (R h). R h (17) max Equation (18) expresses the ilm heat transer oeiient o the perorated surae (h ps). h ps ( ) h (18) max (a)200w 6373

4 RPN Journal o Engineering and pplied Sienes sian Researh Publishing Network (RPN). ll rights reserved. (b)500w Figure-5. Eet o the peroration diameters on the in surae area ratio (RF). ()900W Figure-3. Temperature distribution along x-diretion o the non-perorated and perorated ins. Figure-6. Eet o the peroration diameters on the perorated surae heat transer oeiient ratio (Rh). Figure-4. Eet o the peroration diameters on the weight redution ratio (RWF) o the perorated ins. Figure-7. Eet o the peroration diameters on the ilm heat transer oeiient o the perorated surae (h ps). 6374

5 RPN Journal o Engineering and pplied Sienes sian Researh Publishing Network (RPN). ll rights reserved. Figure-7 presents the eet o the peroration diameters on the ilm heat transer oeiient o the perorated surae (h ps) or dierent heat supply. It an be seen that the inrease o the peroration diameter size led to the inrease o ilm heat transer oeiient. Meanwhile, the ilm heat transer oeiient o the perorated surae (h ps) inreased with the inrease o the heat supply. CONCLUSIONS long the perorated in length the temperature drop is higher than that or non-perorated in. The rate o temperature drop along the perorated in derease with derease o the peroration dimension. The peroration dimension and lateral spaing have the signiiant eet on the gain in the heat dissipation rate o the perorated in. For the perorated in that ontained a larger peroration diameter, the surae heat transer oeiient ratio was higher than that ontained small peroration diameter. The ilm heat transer oeiient o the perorated surae (h ps) inreased with the inrease o peroration diameter and power supply. The inreases o peroration diameter and power supply have signiiant eet on the heat transer rate and the oeiient o heat transer. CKNOWLEDGEMENTS The authors would like to thank Universiti Malaysia Pahang or providing laboratory ailities and inanial support under researh grant (RDU130133). REFERENCES [5] Fujii, M. (2007). Enhanement o natural onvetive heat transer rom a vertial heated plate using inlined ins. Heat Transer sian Researh, 36(6), pp [6] l-essa,.h. yman, M. and mmourah, M.S. (2009). Enhanement o natural onvetion heat transer rom a in by retangular perorations with aspet ratio o two. International Journal o Physial Sienes, 4 (10), pp [7] l-doori, W.H..R., (2011). Enhanement o natural onvetion heat transer rom retangular ins by irular perorations, International Journal o utomotive and Mehanial Engineering, 4, pp [8] Sahin, B. and Demir,. (2008). Perormane analysis o a heat exhanger having perorated square ins. pplied Thermal Engineering, 28, pp [9] Dorigna, E., Vullierme J.J., Broussely, M., Foulon, C. and Mokkadem, M. (2005). Experimental heat transer on the windward surae o a perorated lat plate. International Journal o Thermal Sienes, 44(9), pp [10] meel, B., Huisseune, H., Degroote, J., T Joen, C., De Jaeger, P., Vierendeels, J. and De Paepe M. (2013). On in eiieny in interrupted in and tube heat exhangers, International Journal o Heat and Mass Transer, 60, pp [1] Naik, S. and Probert S.D. (1987). Natural-onvetion harateristis o a horizontally-based vertial retangular in-array in the presene o a shroud. pplied Energy, 28, pp [2] Bayram, S. and lparslan, D. (2008). Perormane analysis o a heat exhanger having perorated square ins pplied Thermal Engineering, 28(5 6), pp [3] Sable, M.J., Jagtap, S.J., Patil, P.S., Baviskar, P.R. and Barve, S.B. (2010). Enhanement o natural onvetion heat transer on vertial heated plate by multiple V-in arrays, International Journal o Researh and Reviews in pplied Sienes, 5 (2), pp [4] Walunj,.., Daund, V.S. and Palande, D.D. (2014). Review o Perormane o Retangular Fins under Natural Convetion at Dierent Orientation o Heat Sink, International Journal o Innovation and pplied Studies, 6(2), pp

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

ISSN-L: 2223-9553, ISSN: 2223-9944 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,