In this work we investigate numerically the forced convective heat transfer of two nanofluids Al2O3/water and TiO2/water in a flat tube of a standard automobile radiator to quantitatively evaluate the enhanced heat transfer characteristics. The heat transfer characteristics of nanofluids under forced convection were investigated for different volumetric concentrations of nanoparticles between 0.25 and 10.0 %, and compared with the base fluid (water). The computational simulations were carried out with the Ansys Fluent software package.info:eu-repo/semantics/publishedVersio

Ribeiro, José Alves

Ribeiro, Luís Frölén

Soares, Armando

English

Biblioteca Digital do IPB

CCKUÍH 3. npiiKjiaflH» riflpoMexaHJKa Ta MexDTpBHiK-aNUMERICAL STUDY ON THE EFFECT OF ALiOaAVATER ANDTI02/WATER NANOFLUIDS ON FORCED CONVECTIVE HEATTRANSFER IN A FLAT TUBESoares, A.A. u, Ribeiro, J. A.1-4 Ribeiro, L.F.2-31-School ofScience and Technology, Universidade de Trás os montes e Alto Douro, Portugal2-Mechanical Technology Department, Instituto Politécnico de Bragança, Portugal3-Centre for Renewáble Energy Research - INEGI - Portugal4-Centre for the Research and Technology ofAgro-Enviromnental and Biological SciencesPonugalAbsíractMost conventional fluids, such as water, ethylene glycol and engine oil, have lünitedthermal capabilities properties, which may impose restrictions m many thennal applications. On theother hand, con-ectly there is an extensive research that hás proven that nanofluids (suspensions ofnanometer-sized metallic particles in a base fluid) are better heat transfer agent than conventionalfluids, e.g. [l]. An ünportant applicatíon ofnanoflluids can be used in retígeration systems such asautomobile radiators with an important impact in the reduction ofthe sizes ofradiators.In this work we investigate numerically the ferced convective heat transfer of twonanofluids AlzOs/water and TiOs/water in a flat tobe of a standard automobile radiator toquantitatively evaluate the enhanced heat transfer characteristics. The heat transfer characteristics ofnanofluids under forced convection were investígated for different volumetric concentrations ofnanoparticles between 0,25 and 10.0%, md compared with the base fluid (water). Tbecomputational simulations were carried out with the Ansys Fluent software pack^e.The focus ofthis research is to compare the flow and heat transfer to the cases where waterproperties are considered constant and dependent ofthe temperature. To the best ofour knowledge,numérica! studies involving nanofluids in the flat tubes of a radiator under the eonditions of thepresent study have not been done só far. Thus, the numerical results obtained were validated forwater flow by comparing the fiicüon factor and the Nusselt number in the flat tube with fheoreticaland empirical results available in the literature.Heat trmsfer results are presented for temperature, convective heat transfer coefRcient, heatflux, Prandtl number and Nusselt number (Nu) in tíie range of conditions studied as well as flowand nanofluids characteristics like fiiction factor, pressure loss, dissipated power, density, viscosity,thermal conductivity and specific heat. The results obtained wiüi nanofluids promise efBcient heattrmsfer to develop more efficient heat transfer fluids for use in automobile motors and industrialequipment, since the presence of alumina and titanium dioxide iianoparticles provide a greatercooling compared with the base fluid (water).For the fluid flow in radiators, the compression work and lhe viscous dissipation arenegligible. Under these conditioiis, we have numerically solved the followmg govemmg equationsunder a 3D flow fíeld using the computation fluid dynamics (CFD.v. =o W^(v. V)v=-V/>+^V-vA/^(v. V)T=^V2r(2)(3)Many studies have shown that the low particle volumetric concentration ofthe nanoparticlesin the base fluid makes it behave like a singie-phase fluid, e.g. [l, 2], The equatíons adopted inpresent work to the thermophysical properties ofnanofluids; density, viscosity, specific heat and241JVIarepia. ïïii XlX-MHTK«nporpeciiBHa TexHÍsca, TCXHOJIO^ÍH Ta iuaíeHepH a ocEÍTa», 2018themial conductivity were obtained from [3, 4]. The volumetric concentrations of nanopartidesranged from 0.25 and 10.0 %. The properties ofwater and nanoparticles were withdrawn fi-om [5,6], Tablel,Tablel.Propertíes ofthe nanopartides and water at temperature of30°CMaterialwaterAhOaTK)2p(kg/m3)995.349388041754179. 642773692t<W7m. <IC)0.6146|3é|S.4Jft(Pa.s)0.00079981The geometry of the flatted tube hás a larger diameter, smaller diameter and length of 9.0, 3.0 and345 mm, respectively [7].The system ofgoveming Eqs. (1)-(3) was solved by the fmite volume mefhod approach usingthe Fluení. Specification on the numerical methods used can be found in our previous work [8, 9].For ali simulations performed, converged solutions were considered when the residuais resultinglïom the iterative process for ali conservative equations were lower than 10 's.The boundaiy conditions used were: on the tube wall are applied the usual no-slip condition(v = 0) and the constant temperature condition (isothennal wall, T = 30°C); at lhe tube oudet wasapplied the conditíon presstve-outlet of Fluent; at the tube inlet was imposed the temperafaire of90°C and in the case of the constant water properties were imposed the velocities of 0.0429 and0. 3434 m/s (calculated for Re = 250 and 2000 for water at 30 °C) and in the case ofthe temperature-dependent water propenies were imposed the velocities 0.0172 and 0. 1376 m/s (calculated for Re =250 and 2000 for water at 90 °C).For the choice of appropriate mesh, additional tests for water flow with constant properties atT = 30°C were carried out for Reynolds numbers fi-om Re = 250 to 2000 in meshes with 21576,46138, 104949 and 159962 nodes. The tests camed out using four meshes showed that the gaúiinaccuracy ofthe fiictíon factor and average Nusselt number which resulted from the use ofthe fmestmesh (159962 nodes) was overall <2%. Then the mesh with 104949 nodes was selected for thepresent stuáy.Some ofthe results obtamed in this researeh are shown in the Figures l ana 2. Figure l showsthe average temperature along the flatted tube. The temperature decreases along the tube and withthe concentradon of nanoparticles. Both nanofluids show the same behaviour. In the case of theconstant water properties. Figure l(a) and (b), for AliOj and Re = 250 the temperature decreases46. 56 K and 50.47 K for concentrations 0.0% and 10. 0% respectively, whereas for Re = 2000decreases 23.37 K and 25. 58 K for concentrations 0.0% and 10. 0%, respectively. For concentrationof 10. 0% and TiOz/water (he temperature decreases about 2 K less than for Al203/water.In the case ofthe temperature-dependent water properties. Figure l (c) and (d), the temperaturedecrease is more pronounced. For A1203 and Re = 250, the temperature decreases 57. 03 K md58. 69 K for concentrations 0. 0% and 10. 0%, respectively. For AI203 and /?e=2000, thetemperature decreases 33. 42 K and 35. 90 K for concentrations 0.0% and 10. 0%, respectively. Forconcentration of 10. 0% and TiOi/water the temperature decreases about 1. 5 K less than forAhOs/water.Figure 2 shows, for Re =250, the variations of local Nusselt number (Nu) along the line-1 andline-2 (see flat tube representation in the upper right comer of Figure 2). Line-1 is located on theplan wall md line-2 is located on the curved wall. Nu decreases along both lines however thatdecrease is more pronounced in the line-2 because that line is fúrther away from the center ofthetube. An increase in the nanoparticles concentration results in a decrease in Nu for bothnanoparticles. However, this decrease is slighüy higher for A1203.242CeK-uin 3. npiiKjiaflHa rwpowexaHÍKa T;I wexaTpouÍKa0. 1 0.2 0.3Posltion (m)Figure l. Temperature along the hibe as a fünction ofnanupartide concentration, for Se = 150 and Re = 2000 atthe tube inlet For the cases of the constant water properties (a) Ah03 and (b) TiO;, and temperature-dependentwater propertics, (c) AhOjantí (d) Ti02.100.0 a-0.0% - -4.0% -](). ()"/«Al, 0,liac-1O. IB 0.20 0. 30PtKÍtíon (m)Figure 2. Nu a!ong the Iine-1 and line-2 as a function of nanoparticle concentration, for Re c 250 at (hetube inlet. For the case ofthe constant water properties (a) AbOa, (b) TiOi, and tempErature-dependent waterproperties (c) AbOi, (d) TÍ02.243Ma repia. illi X1X-MHTK «UporpfCllBHa TexHÍk-a, TexHojiorin Ta ÍHiKeHFpna ocBÍra», 201 8Referentes[l] Maiga, S. B., Palm, S.J., Nguyan, C. T., Roy, G., Galanis, N. (2005), Heat trmster enbancement by usingnanofluids in forced convectíon flows. Int. J. Heat FIuid Flow, 26: 530-546.[2] Akbarinia, A., Behzadmehr, A. (2007), Numerical stody of laminar mixed convection of a nanofluid inhorizontal curved tubes, Appl. Thenn. Eng., 27, (S-9): 1327-1337.[3] Vanaki, Sh. M,, Gmesan, P., Mohammed, H. A. (2016), Numerical study of coavective heat transfer ofnanofluids: A review, Renewable md Sustainable Energy Reviews, 54: 1212-1239.[4] Pak, B. C., Cho, Y. I. (1998), Hydrodynamic and heat transfer study of dispersed fluids with submicroDmetallic oxide partides, Intemational Joumal of Experimental Heat Transfer, 11:151-70.[5] Pramuditya, S. (2011), Water thermodynamic properties. Physics Dqianment - Technical Document.http://portal. fi. itb. ac. id/tecdoc/wateiprop/.[é] Shanna, K. V., Sharma, P. K., Azmi, W. H., Rizalman, M., Kaáirgama, K. (2012). Correlations to predictfnction and forced convection heat traasfer coefBcients of water base nanofluids ft» hirbulent flow in a tube, TheIntemational Joumal ofMicroscale and Nanoscale Thermal md Fluid Trmsport Phenomena, 3, (4): 1-25.[7] Hussein, A. M. Bakar, R. A., Kadirgama, K., Sharma, K. V. (2014), Heat üansfer augmentation of a carradiator using nanofluids, Heat Mass Transfer, 50: 1553-1561 ,[8] Sousa, P,, Soares, A., Monteiro, E., Rouboa, A. (2014), A CFD study ofthe hydrodynamics in a desalinationmembrane filled with spaceis, Desalination, 349:22-30.[9] Soares, A. A., Silva, J., Monteü-o E,, Rouboa A. (2017), Pulsating flow effects on hydrodynamics in adesalination membrane filled with spacers, Desalination. DÓI: 10. 5772/intechopen. 68777.y/(K 637. 134ri^POAHHAMNHA OBPOEKA MOJIOKA RPHTFAHCHOPTyBAHHIBouaapeHKO P.M., CeMÍKCbKa H.B.KFÍI ÍM. Iropa CÍKOpcbKoro, M. 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Numerical study on the effect of Al2O3/water and TiO2/water nanofluids on forced convective heat transfer in a flat tube

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Numerical study on the effect of Al2O3/water and TiO2/water nanofluids on forced convective heat transfer in a flat tube

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