Mixed Convection Characteristics of Ethylene Glycol and Water Mixture Based Al2O3 Nanofluids

Transcription

1 Proceeding o the 2 nd World Congre on Mechanical, Chemical, and Material Engineering (MCM'16) Budapet, Hungary Augut 22 23, 2016 Paper No. HTFF 116 DOI: /ht Mixed Convection Characteritic o Ethylene Glycol and Water Mixture Baed Al2O3 Nanoluid Eli Büyü Öğüt 1, Kamil Kahveci 2 1 Vocational School o Gebze, Kocaeli Univerity, Heree-Kocaeli / Turey eli.ogut@ocaeli.edu.tr 2 Mechanical Engineering Department, Traya Univerity, Edirne / Turey amil@traya.edu.tr Abtract Mixed convection o ethylene glycol (EG) and water mixture baed Al 2O 3 nanoluid in a lid-driven quare encloure heated rom the let wall and cooled rom the top wall wa invetigated numerically in thi tudy. The Graho number wa ept at a contant value o Reynold number wa aumed to vary in a range o that the Richardon number get value in the range o 0.1 to 10. Three dierent nanoparticle volume raction were conidered: 0%, 4% and 8%. Six dierent volume ratio o EG to water were taen into conideration, 0:100 %, 20:80 %, 40:60%, 60:40%, 80:20% and 100:0%. The reult how that an increae in the average Nuelt number i een with an increae in the volume raction o nanoparticle and with a decreae in the Richardon number. The reult alo how that average Nuelt number how a coniderable increae with an increae o EG volume raction in the bae luid. Keyword: Mixed convection, quare encloure, nanoluid, water, ethylene glycol. 1. Introduction Conventional heat traner luid uch a water, oil and ethylene glycol ha a low thermal conductivity. Thi i the primary limitation in enhancing the perormance and compactne o many electronic device in engineering. To improve the thermal conductivitiy o a luid olid particle in nano ize are added into a bae luid. The reulting mixture, reerred to a a nanoluid, ha a coniderably higher thermal conductivity than that o the bae luid [1]. Anomalou increae in thermal conductivity can be attributed to the our actor: Brownian motion, molecular-level layering o the liquid, the nature o heat traner mechanim and the nanoparticle clutering [2]. There are a coniderable number o tudie in the literature on natural and orced convective heat traner o nanoluid [3-7].On the other hand, tudie on mixed convection heat traner are relatively limited. In one o thee tudie, Abarinia and Behzadmehr [8] conducted a numerical tudy on ully developed laminar mixed convection o a nanoluid in a horizontal curved tube. Their reult how that, or a given Reynold number, buoyancy orce ha a negative eect on the Nuelt number while the nanoparticle concentration ha a poitive eect on heat traner enhancement and alo on in riction reduction. Kahveci and Ogut [9] tudied mixed convection o water-baed nanoluid in a lid-driven quare encloure with a contant heat lux heater. The reult how that the heat traner rate increae coniderably with a decreae in the Richardon number and length o the heater. Kalteh et al. [10] made a numerical invetigation on laminar mixed convection low o water-baed nanoluid in a lid-driven quare cavity with a triangular heat ource. The reult how that increaing the nanoparticle diameter lead to a decreae in the average Nuelt number or all Richardon number. The reult alo how that the average Nuelt number increae by a decreae in the heat ource height. Keayati [11] tudied mixed convection o non- Newtonian nanoluid in a lid-driven encloure with inuoidal temperature proile. The reult indicate that the eect o nanoparticle on the enhancement o heat traner decreae with an increae in the power-law index. Garooi and Hoeininejad [12] conducted a numerical tudy on natural and mixed convection heat traner between dierentially heated cylinder in an adiabatic encloure illed with nanoluid. Their reult indicate that heat traner rate may increae or decreae by changing rotation direction o the hot and cold cylinder, and it i ound that, by changing the location o the heat ource/in rom bottom top to top bottom coniguration, heat traner rate decreae igniicantly. Their reult alo how that average Nuelt number reduce dramatically by a change o the poition o the cold cylinder rom vertical to horizontal mode. Ahmet et al. [13] numerically invetigated mixed convection rom a dicrete heat ource in encloure with two adjacent moving wall and illed with nanoluid. Their reult how that both the Richardon number and moving lid ordination have a HTFF 116-1

2 igniicant eect on the low and thermal ield in the encloure. Haib et al. [14] tudied the eect o tilt angle on mixed convection low in trapezoidal cavitie illed with water-al 2O 3 nanoluid. Their reult how that tilting the encloure increae heat traner rom heated wall or hort baed trapezoid, while it decreae or long baed trapezoid. Water, ethylene glycol or propylene glycol are uually ued a ingle bae luid in a bae luid-nanoluid- mixture. On the other hand, the ue o water + glycol mixture a bae luid combine the advantage o both pure compound, ince mixture exhibit higher thermal conductivity than their pure glycol and a lower reezing point than water [15]. Thereore, glycoled water i ued in a large number o practical application uch a antireeze in car engine or traner medium in olar heating intallation [16, 17]. Accordingly, mixed convection o EG/ water mixture baed Al 2O 3 nanoluid in a liddriven quare encloure heated rom one ide and cooled rom the tationary adjacent ide wall wa invetigated numerically in thi tudy to reveal the eect o governing parameter on the heat traner and luid low. 2. Analyi The geometry and the coordinate ytem ued in the analyi are een in Fig. 1. Nanoluid inide the encloure wa aumed to be heated and cooled by the let and top wall at uniorm temperature o T H and T C, repectively. The right and bottom wall o the encloure were aumed to be adiabatic. The hot vertical wall wa alo aumed to move in poitive y direction with a contant velocity. The nanoluid in the encloure wa aumed to be Newtonian and incompreible, and low wa aumed laminar. It wa alo aumed that both the luid particle and nanoparticle are in a thermal equilibrium and they low at the ame velocity. The thermo-phyical propertie o the nanoluid were aumed contant except or the denity in the buoyancy orce term. The vicou diipation term and the thermal radiation were alo aumed to be negligible. Fig. 1: Geometry and the coordinate ytem. In order to nondimenionalize the governing equation, ollowing dimenionle variable were ued: x * y * x, y, (1) L L * u * v* p T TC u, v, p, 2 (2) U U U T T, 0 where g i gravitational acceleration, L i the dimenional length o the quare encloure, U i the velocity o the hot vertical wall, u* and v* are the dimenional velocitie in the x* and y* direction, repectively, p* i the dimenional preure,,0 i the denity o the luid at temperature T C and i the nondimenional temperature. With thee dimenionle variable, nondimenional governing equation in vorticity-tream unction ormulation tae the ollowing orm: Stream unction equation: H C HTFF 116-2

3 (3) x y Vorticity tranport equation: v x y 1 Re 1 x y Gr Re n u 2 n,o n,o x (4) Energy equation: n where n. c p n, 0 n 1 u v (5) x y Re Pr x y The Reynold, Prandtl, and Graho number in the governing equation are deined a: 2 3 U L g L (T T ),0, H 0 C Re, Pr, Gr, (6) 2,0 where i the vicoity, i the thermal expanion coeicient and α i the thermal diuivity o the luid. In thi tudy, the vicoity o the nanoluid wa aumed to be predicted by the Brinman model [18]: n (7) The denity, heat capacitance and Bouineq term o nanoluid can be expreed by the ollowing relation [19]: ( (8) p n,o 1 ) n,o,o 1 c p c p ( c ) (9) ( ) n 1 (10) where, i the volume raction o olid particle and ubcript, n and tand or bae luid, nanoluid and olid, repectively. The Yu and Choi [20] model wa ued in thi tudy or the thermal conductivity prediction o nanoluid: n (11) where i the ratio o the nanolayer thicne to the original particle radiu. The governing equation are ubjected to the ollowing boundary condition: ( x,0) 0, (x,1) 0, (0,y) 0, (1,y) 0 (12) HTFF 116-3

4 0, 0, 1, y y x x0 x x1 y0 (0, y) 1, y1 (x,1) 0, x x1 0, y y0 0 0 (13) (14) wall The boundary condition or the vorticity on the wall i expreed rom the tream unction equation a /, where i the outward direction normal to the urace. The local Nuelt number along the hot wall o the encloure can be deined a: where Q ( n) tagnant Nu (15) Q x cond,luid T Q ( n) tagnanta (16) x * x* 0 The average Nuelt number on the hot wall can then be deined by the ollowing relation: Nu a 1 Nu dy (17) 0 3. Reult and Dicuion The thermo-phyical propertie o the bae luid and nanoparticle ued in thi tudy are hown in Table 1 The Graho number wa aumed contant at a value o 10 4, and the Reynold number i varied uch that the Richardon number get value in the range o The Richardon number determining the ratio o the buoyancy orce to the hear orce i deined a Ri=Gr/Re 2. Three dierent nanoparticle volume raction were taen into conideration: 0, 4 and 8 and the value o the ratio o the nanolayer thicne to the original particle radiu, wa ixed to 0.1. The computational reult were obtained or ix dierent volume ratio o EG to water, 0:100%, 20:80%, 40:60%, 60:40%, 80:20%, 100:0 %. The olution o the governing equation were obtained by Comol Multiphyic inite element modelling and imulation otware. Table 1: Thermophyical propertie. Property 0:100% 20:80% 40:60% 60:40% 80:20% 100:0% Al 2O 3 (g/m 3 ) c p (j/g K) (W/m K) µ(mpa/) x10 7 (m 2 /) (K -1 ) Pr The treamline and iotherm in the encloure are hown in Figure 2 or pure water a bae luid. A it can be een, low in the encloure i unicellular or all value o Ri number and olid volume raction. The heated luid particle rie along the let wall a a reult o buoyancy orce and hear orce until they reach the top wall, where they turn rightward, toward the idewall, while they are cooled by the top wall. Then they turn downward and the retriction impoed by the bottom HTFF 116-4

5 wall orce them to turn letward. The low path i completed a the colder luid particle are entrained to the acending low along the hot wall. The boundary-layer low regime i clearly een in the encloure by the teepne o the iotherm near the vertical let wall and horizontal top wall. For low value o Ri number, low i hear dominated. Thereore, an increae in the nanoparticle volume raction doe mot eect the low ield coniderably. However, circulation intenity how an increae with an increae in the nanoparticle olid volume raction when the Ri number get higher value. For high value o Ri number, low i buoyancy dominant and energy tranport rom the hot wall to the luid increae with an increae in the olid volume raction a a reult o higher thermal conductivity o the nanoluid. A hown in igure, the clutering o iotherm near the hot wall decreae with an increae in the olid volume raction becaue o increae in the thermal diuion. The treamline and iotherm in the encloure are given in Figure 3-5 or variou value o EG to water volume ratio. A it can be oberved rom igure that an increae in EG volume raction ha no igniicant eect on low ield or low value o the Richardon number. With an increae in the Richardon number circulation intenity get lower value with an increae in the ethylene glycol volume raction. For high value o Richardon number, low i buoyancy dominant. An increae in the ethylene glycol ratio reult in an increae in the Prandtl number. For high vale o Prandtl number, the vicou orce i dominant over the thermal orce. Thereore, circulation intenity weaen by an increae o Prandtl number or high value o Richardon number. With an increae in the EG volume ratio, thereore in Prandtl number, iotherm become more condened near the hot wall. Thi i becaue o the act that thermal boundary layer get thinner with an increae in the Prandtl number. a) Ri=0.1 =0.0 =0.08 b) Ri=1 =0.0 =0.08 c) Ri=10 =0.0 =0.08 Fig. 2: Streamline (on the let) and iotherm (on the right) or 0:100% baed nanoluid. HTFF 116-5

6 a) Ri=0.1 =0.0 =0.08 b) Ri=1 =0.0 =0.08 c) Ri=10 =0.0 =0.08 Fig. 3: Streamline (on the let) and iotherm (on the right) or 20:80% baed nanoluid. a) Ri=0.1 =0.0 =0.08 b) Ri=1 =0.0 =0.08 c) Ri=10 =0.0 =0.08 Fig 4: Streamline (on the let) and iotherm (on the right) or 80:20% baed nanoluid. HTFF 116-6

7 a) Ri=0.1 =0.0 =0.08 b) Ri=1 =0.0 =0.08 c) Ri=10 =0.0 =0.08 Fig 5: Streamline (on the let) and iotherm (on the right) or 100:0% baed nanoluid. Variation o the average Nuelt i hown in Table 2 or variou value o governing parameter. A it can be een rom Table 2, average Nuelt number get higher value or low value o Richardon number. For low value o Richardon number, hear orce are dominant over buoyancy orce. Fluid particle along the hot wall are carried toward the cold wall by the movement o hot wall in vertical direction. Thi reult in a higher temperature gradient on the hot wall. Thereore, the average Nu number get higher value. A it can alo be oberved rom Table 2 that olid volume raction ha a igniicant eect on average Nuelt number and it how an increae with an increae in the olid particle volume raction. Average Nuelt number how a igniicant increae with an increae in the Prandtl number depending on the increae in the ethylene glycol volume raction in the bae luid. Thi i becaue o the act that luid with the highet Prandtl number i capable to carry more heat away rom the hot wall in the encloure. Table 2: Variation o the average Nuelt number. Ri :100% 20:80% 40:60% 60:40% 80:20% 100:0% HTFF 116-7

8 4. Concluion The preent tudy conider laminar, mixed convection low o nanoluid in a quare encloure heated rom let wall that move with a contant velocity and cooled rom the tationary adjacent top wall. The other wall are tationary and adiabatic. Heat traner enhancement o ethylene glycol and water mixture baed Al 2O 3 nanoluid i tudied numerically or a range o Richardon number, volume raction, and volume ratio o ethylene glycol to water. The reult how that the addition o nanoparticle increae the heat traner rate. Reult alo how that heat traner rate increae with a decreae in Richardon number. Finally, reult how that the average Nu number how a coniderable increae with an increae o ethylene glycol volume raction in the bae luid. Reerence [1] J. A. Eatman, S. U. S. Choi, S. Li, W. Yu, and L. J. Thompon, Anomalouly increaed eective thermal conductivitie o Ethylene glycol-baed nanoluid containing Copper nanoparticle, Appl Phy Lett, vol. 78, pp , [2] P. Keblini, S. R. Phillpot, S. U. S Choi, and J. A. Eatman, Mechanim o heat low in upenion o nano-ized particle (nanoluid), Int J Heat Ma Traner, vol. 45, pp , [3] K. Khanaer, K. Vaai, and M. Lighttone, Buoyancy-driven heat traner enhancement in a two-dimenional encloure utilizing nanoluid, Int J Heat Ma Traner, vol. 46, pp , [4] R. Y. Jou and S. C. Tzeng, Numerical reearch o nature convective heat traner enhancement illed with nanoluid in rectangular encloure, Int Commun Heat Ma Traner, vol. 33, pp , [5] E. B. Ogut, Natural convection o water-baed nanoluid in an inclined encloure with a heat ource, International Journal o Thermal Science, vol. 48, pp , [6] S. M. Vanai and H. A. Mohammed, Numerical tudy o nanoluid orced convection low in channel uing dierent haped tranvere rib, Int. Comm. in Heat and Ma Traner, vol. 67, pp , [7] R. Nebbatia and M. Kadjab, Study o orced convection o a nanoluid ued a a heat carrier in a microchannel heat in, Energy Procedia, vol. 74, pp , [8] A. Abarinia and A. Behzadmehr, Numerical tudy o laminar mixed convection o a nanoluid in horizontal curved tube, Applied Thermal Engineering, vol. 27, pp , [9] K. Kahveci and E. B. Öğüt, Mixed convection o water-baed nanoluid in a lid-driven quare encloure with a heat ource, Heat Traner Reearch, vol. 42, pp , [10] M. Kalteh K. Javaherdeh, and T. Azarbarzin, Numerical olution o nanoluid mixed convection heat traner in a liddriven quare cavity with a triangular heat ource, Powder Technology, vol. 253 pp , [11] G. H. R. Keayati, Mixed convection o non-newtonian nanoluid low in a lid-driven encloure with inuoidal temperature proile uing FDLBM, Powder Technology, vol. 266, pp , [12] F. Garooi and F. Hoeininejad, Numerical tudy o natural and mixed convection heat traner between dierentially heated cylinder in an adiabatic encloure illed with nanoluid, Journal o Molecular Liquid, vol. 215, pp. 1 17, [13] S. E. Ahmed, M. A. Manour, A. K. Huein, and S. Sivaanaran, Mixed convection rom a dicrete heat ource in encloure with two adjacent moving wall and illed with micropolar nanoluid, Engineering Science and Technology, an International Journal, vol. 19, pp , [14] M. H. Haib, Md. S. Hoen, and S. Saha, Eect o tilt angle on pure mixed convection low in trapezoidal cavitie illed with water-al 2O 3 nanoluid, Procedia Engineering, vol. 105, pp , [15] D. Cabaleiro, L. Colla, F. Agreti, L. Lugo, and L. Fedele, Tranport propertie and heat traner coeicient o ZnO/(ethylene glycol + water) nanoluid, Int. J. o Heat and Ma Traner, vol. 89, pp , [16] S. Z. Heri, M. Shorgozar, S. Poorpharhang, M. Shanbedi, and S. H. Noie, Experimental tudy o heat traner o a car radiator with CuO/ethylene glycol-water a a coolant, J. Diper. Sci. Technol., vol. 35 pp , [17] Z. Said, M. H. Sajid, M. A. Alim, R. Saidur, and N. A. Rahim, Experimental invetigation o the thermophyical propertie o Al 2O 3-nanoluid and it eect on a lat plate olar collector, Int. Commun. Heat Ma, vol. 48 pp , [18] H. C. Brinman, The vicoity o concentrated upenion and olution, J. Chem Phy, vol. 20, pp , HTFF 116-8

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