2014
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89
Prediction of Pressure Drop of Al2O3Water Nanofluid in Flat Tubes Using CFD and Artificial Neural Networks
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2
In the present study, Computational Fluid Dynamics (CFD) techniques and Artificial Neural Networks (ANN) are used to predict the pressure drop value (Δp ) of Al2O3water nanofluid in flat tubes. Δp is predicted taking into account five input variables: tube flattening (H), inlet volumetric flow rate (Qi ), wall heat flux (qnw ), nanoparticle volume fraction (Φ) and nanoparticle diameter (dp ). The required output data for training the ANN are taken from the results of numerical simulations. The numerical simulations of nanofluid are performed using two phase mixture model by FORTRAN programming language. The flow regime and the wall boundary conditions are assumed to be laminar and constant heat flux respectively. The ANN results are compared with the numerical simulated one and excellent agreement is observed. To view the accuracy of ANN model, statistical measures R2 , RMSE and MAPE are used and it is seen that the ANN model has high accuracy in predicting the (Δp ) values.
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1
13


H.
Safikhani
Department of Mechanical Engineering, Amirkabir University of Technology, Tehran, I.R. Iran
Department of Mechanical Engineering, Amirkabir
Iran


A.
Abbassi
Department of Mechanical Engineering, Amirkabir University of Technology, Tehran, I.R. Iran
Department of Mechanical Engineering, Amirkabir
Iran


S.
Ghanami
Department of Mechanical Engineering, University of Sistan & Baluchestan, Zahedan, I.R. Iran
Department of Mechanical Engineering, University
Iran
ANN
GMDH
Mixture model
Nanofluid
Pressure drop
[[1] S.K. Das, N. Putra, P.W. Thiesen, R. Roetzel, Temperature dependence of thermal conductivity enhancement for nanofluids, J. Heat Transfer, 125 (2003) 567574. ##[2] S.M.S. Murshed, K.C. Leong, C. Yang, A combined model for the effective thermal conductivity of nanofluids, Appl. Thermal Eng. 29 (2009) 24772483. ##[3] T.P. Teng, Y.H. Hung, T.C. Teng, H.E. Mo, H.G. Hsu, The effect of alumina/water nanofluid particle size on thermal conductivity, Appl. Thermal Eng. 30 (2010) 22132218. ##[4] E. EbrahimniaBajestan, H. Niazmand, W. Duangthongsuk, S. Wongwises, Numerical investigation of effective parameters in convective heat transfer of nanofluids flowing under a laminar flow regime, Int. J. Heat Mass Transfer 54 (2011) 4376–4388. ##[5] M. Kalteh, A. Abbassi, M. SaffarAvval, J. Harting, Eulerian–Eulerian twophase numerical simulation of nanofluid laminar forced convection in a microchannel, Int. J. Heat Fluid Flow 32 (2011) 107–116. ##[6] R. Lotfi, Y. Saboohi, A.M. Rashidi, Numerical study of forced convective heat transfer of Nanofluids: Comparison of different approaches, Int. Commun. Heat Mass Transfer 37 (2010) 74–78. ##[7] M. Shariat, A. Akbarinia, A. Hossein Nezhad, A. Behzadmehr, R. Laur, Numerical study of two phase laminar mixed convection nanofluid in elliptic ducts, Appl. Therm. Eng. 31 (2011) 23482359. ##[8] P. Razi, M.A. AkhavanBehabadi, M. Saeedinia, Pressure drop and thermal characteristics of CuO–base oil nanofluid laminar flow in flattened tubes under constant heat flux, Int. Commun. Heat Mass Transfer 38 (2011) 964–971. ##[9] R.S. Vajjha, D.K. Das, P.K. Namburu, Numerical study of fluid dynamic and heat transfer performance of Al2O3 and CuO nanofluids in the flat tubes of a radiator, Int. J. Heat Fluid Flow 31 (2010) 613–621. ##[10] S.J. Farlow, Selforganizing Method in Modeling: GMDH type algorithm. Marcel Dekker Inc, 1984. ##[11] N. NarimanZadeh, A. Darvizeh, R. AhmadZadeh, Hybrid genetic design of GMDHtype neural networks using singular value decomposition for modeling and prediction of the explosive cutting process, J. Eng. Manufact. 217 (2003) 779–790. ##[12] N. Amanifard, N. NarimanZadeh, M.H. Farahani, A. Khalkhali, Modeling of multiple shortlengthscale stall cells in an axial compressor using evolved GMDH neural networks, Energy Convers. Manag. 49 (2008) 2588–2594. ##[13] H. Safikhani, M.A. AkhavanBehabadi, N. NarimanZadeh, M.J. Mahmoodabadi, Modeling and multiobjective optimization of square cyclones using CFD and neural networks, Chemical Eng. Research Design 89 (2011) 301–309. ##[14] M.J. Wilson, T.A. Newell, J.C. Chato, C.A.I. Ferreira, Refrigerant charge, pressure drop and condensation heat transfer in flattened tubes, Int. J. Refrig. 26 (2003) 442–451. ##[15] J. Quiben, L. Cheng, J. Da Silva, J. R. Thome, Flow boiling in horizontal flattened tubes: Part I – Twophase frictional pressure drop results and model, Int. J. Heat Mass Transfer 52 (2009) 3645–3653. ##[16] M. Nasr, M. A. AkhavanBehabadi, S. E. Marashi, Performance evaluation of flattened tube in boiling heat transfer enhancement and its effect on pressure drop, Int. Commun. Heat Mass Transfer 37 (2010) 430–436. ##[17] M. Manninen, V. Taivassalo, S. Kallio, On the mixture model for multiphase flow. VTT Publications, 1996. ##[18] L. Schiller, A. Naumann, A drag coefficient correlation. Z. Ver Deutsch Ing, 1935. ##[19] B. Pak, Y. Cho, Hydrodynamic and heat transfer study of dispersed fluids with submicron metallic oxide particles, Exp. Heat Transfer 11 (1998) 151–170. ##[20] Y. Xuan, W. Roetzel, Conceptions for heat transfer correlation of nanofluids, Int. J. Heat Mass Transfer 43 (2000) 3701–3707. ##[21] N. Masoumi, N. Sohrabi, A. Behzadmehr, A new model for calculating the effective viscosity of nanofluids, J. Appl. Physics 42 (2009) 055501 (6). ##[22] C. H. Chon,K. D. Kihm, S. P. Lee, S. U. S. Choi, Empirical correlation finding the role of temperature and particle size for nanofluid (Al2O3) thermal conductivity Enhancement, J. Appl. Physics 87 (2005) 153107 (3). ##[23] K. Khanafer, K. Vafai, M. Lightstone, Buoyancy driven heat transfer enhancement in a two dimensional enclosure utilizing nanofluids, Int. J. Heat Mass Transfer 46 (2003) 36393653. ##[24] A. Bejan, Convective heat transfer. John Wiley & Sons Inc, 2004. ##[25] S. V. Patankar, Numerical Heat Transfer Fluid Flow. Washington: Hemisphere, 1980. ##[26] R. K. Shah, A. L. London, Laminar Flow Forced Convection in Ducts. New York: Academic Press, 1978. ##[27] S. Mirmasoumi, A. Behzadmehr, Effect of nanoparticles mean diameter on mixed convection heat transfer of a nanofluid in a horizontal tube, Int. J. Heat Fluid Flow 29 (2008) 557566. ##[28] A. G. Ivakhnenko, Polynomial theory of complex systems. IEEE Trans Sys Man Cybern. SMC1, 1971. ##[29] C. Douglas Montgomery, Design and Analysis Experiments. John Wiley & Son Inc, 1991. ##[30] T. H. Hou, C. H. Su, W. L. Liu, Parameters optimization of a nanoparticle wet milling process using the Taguchi method, response surface method and genetic algorithm, Powder Technolog. 173 (2007) 153–162.##]
Single Walled Carbon Nanotube Effects on Mixed Convection heat Transfer in an Enclosure: a LBM Approach
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The effects of Single Walled Carbon Nanotube (SWCNT) on mixed convection in a cavity are investigated numerically. The problem is studied for different Richardson numbers (0.110), volume fractions of nanotubes (01%), and aspect ratio of the cavity (0.52.5) when the Grashof number is equal to 103. The volume fraction of added nanotubes to Water as base fluid are lowers than 1% to make dilute suspensions. The Study presents a numerical treatment based on LBM to model convection heat transfer of Carbon nanotube based nanofluids. A theoretical model is used for effective thermal conductivity of the nanofluid containing Carbon nanotubes. This model covers different phenomena of energy transport in nanofluids. Also, an analytical model is applied for effective viscosity of the nanofluid which includes the Brownian effect and other physical properties of nanofluids. Results show that adding a low value of SWCNT to the base fluid led to significant enhancement of convection heat transfer. Make a comparison between the obtained results and other published papers shows that Carbon nanotubes enhances the rate of convection heat transfer better than other nanoparticles.
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28


M.
Jafari
Mechanical Engineering Department, University of Technology Babol, Babol, I.R. Iran
Mechanical Engineering Department, University
Iran


M.
Farhadi
Mechanical Engineering Department, University of Technology Babol, Babol, I.R. Iran
Mechanical Engineering Department, University
Iran


K.
Sedighi
Mechanical Engineering Department, University of Technology Babol, Babol, I.R. Iran
Mechanical Engineering Department, University
Iran
Effective Thermal Conductivity
Effective Viscosity
Lattice Boltzmann method
LidDriven Cavity
Mixed convection
Nusselt Number
Richardson number
Single Walled Carbon Nanotube (SWCNT)
[[1] F.D.S. Marquis , L.P.F. Chibante: Improving the heat transfer of nanofluids and nano lubricants with Carbon nanotubes, JOM Res. Summary Carbon Nanotubes, December (2005). ##[2] R.K. Tiwari, M.K. Das: Heat transfer augmentation in a twosided liddriven differentially heated square cavity utilizing nanofluids, Int. J. Heat Mass Transfer, 50 (2007) 20022018. ##[3] J.A. Eastman, S.U.S Choi, S. Li, W. Yu, L.J. Thompson: Anomalously increased effective thermal conductivities of ethylene glycolbased nanofluids containing copper nanoparticles, Appl. Phys. Lett., 78 (2001) 718724. ##[4] H. Xie, J. Wang, T. Xi, Y. Liu, F. Ai: Thermal conductivity enhancement of suspensions containing nanosized alumina particles, J. Appl. Phys., 10 (2002) 45684572. ##[5] S.U.S. Choi, Z.G. Zhang, W. Yu, F.E. Lockwood, E.A. Grulke: Anomalous thermal conductivity enhancement in nanotube suspensions, Appl. Phys. Lett., 79 (2001) 22522256. ##[6] H. Xie, H.W. Youn, M. Choi: Nanofluids containing multiwalled Carbon nanotubes and their enhanced thermal conductivities, J. Appl. Phys., 94 (2003) 49674973. ##[7] U.S. Choi: Enhancing thermal conductivity of fluids with nanoparticles, Developments and application of nonNewtonian flows, ASME J. Heat Transfer, 66 (1995) 99105. ##[8] K. Khanafer, K. Vafai, M. Lightstone: Buoyancydriven heat transfer enhancement in a twodimensional enclosure utilizing nanofluids, Int. J. Heat Mass Transfer, 46 (2003) 36393653. ##[9] I. Gherasim, G. Roy, C.T. Nguyen, D. VoNgoc: Experimental investigation of nanofluids in confined laminar radial flows, Int. J. Therm. Sci., 48 (2009) 14861493. ##[10] H. Saleh, R. Roslan ,I. Hashim: Natural convection heat transfer in a nanofluidfilled trapezoidal enclosure, Int. J. Heat Mass Transfer, 54 (2011) 194201. ##[11] S. Mirmasoumi ,A. Behzadmehr: Numerical study of laminar mixed convection of a nanofluid in a horizontal tube using twophase mixture model, Appl. Therm. Eng., 28 (2008) 717727. ##[12] O. Ghaffari, A. Behzadmehr: Investigation of the effect of nanoparticles mean diameter on turbulent mixed convection of a nanofluid in a horizontal curved tube using a two phase approach, Transport Phenomena in Nano and Micro Scales, 1 (2013) 6474. ##[13] A.K. Santra, S. Sen, N. Chakraborty: Study of heat transfer augmentation in a differentially heated square cavity using copperwater nanofluid, Int. J. Therm. Sci., 47 (2008) 11131122. ##[14] M. Izadi, A. Behzadmehr, D. JalaliVahida: Numerical study of developing laminar forced convection of a nanofluid in an annulus, Int. J. Therm. Sci., 48 (2009) 21192129. ##[15] S. Iijima, T. Ichihashi: Singleshell Carbon nanotubes of 1nm diameter, Nature, 363 (1993) 603 605. ##[16] E. T. Thostenson, Z. Ren and T.W. Chou: Advances in the science and technology of Carbon nanotubes and their composites: a review, Compos. Sci. Technol., 61 (2001) 18991912. ##[17] S. Berber, Y.K. Kwon, D. Tomanek: Unusually high thermal conductivity of Carbon nanotubes, Phys. Rev. Lett., 84 (2000) 46134616. ##[18] P. Kim, L. Shi, A. Majumdar, P.L. Mceuen, Thermal transport measurements of individual multi walled nanotubes, Phys. Rev. Lett., 87 (2001) 215502215505. ##[19] A. Gavili, T. Dallali Isfahani, J. Sabbaghzadeh: The variation of heat transfer in a twosided liddriven differentially heated square cavity with nanofluids containing Carbon nanotubes for physical properties of fluid dependent on temperature, Int. J. Numer. Meth. Fluids, 68 (3) (2011) 302323. ##[20] A. Mohamad, Applied Lattice Boltzmann Method for Transport Phenomena, Momentum, Heat and Mass Transfer, Sure, Calgary, 2007. ##[21] M. Jafari, M. Farhadi, K. Sedighi, E. Fattahi: Lattice Boltzmann simulation of mixed convection in an inclined cavity with a wavy wall, Heat TransferAsian Research, 41 (5) (2012) 371387. ##[22] E. Fattahi, M. Farhadi, K. Sedighi: Natural Convection and Entropy Generation in LShaped Enclosure Using Lattice Boltzmann Method, Transport Phenomena in Nano and Micro Scales, 1 (2013) 118. ##[23] M. Aghajani Delavar, M. Farhadi, K. Sedighi: Numerical simulation of direct methanol fuel cells using lattice Boltzmann method, Int. J. Hydrog. Energy, 35 (2010) 93069317. ##[24] E.J. Javaran, S.A.G. Nassab, S. Jafari: Thermal analysis of a 2D heat recovery system using porous media including lattice Boltzmann simulation of fluid flow, Int. J. Therm. Sci., 49 (2010) 10311041. ##[25] E. Fattahi, M. Farhadi, K. Sedighi, H. Nemati: Lattice Boltzmann simulation of natural convection heat transfer in nanofluids, Int. J. Therm. Sci., 52 (2012) 137144. ##[26] M. Jafari, M. Farhadi, K. Sedighi: Effect of Wavy Wall on Convection Heat Transfer of WaterAl2O3 Nanofluid in a Liddriven Cavity Using Lattice Boltzmann Method, Int. J. Engine.  Transaction (A), 25 (2012) 168180. ##[27] H. Nemati, M. Farhadi, K. Sedighi, E. Fattahi: Lattice Boltzmann simulation of nanofluid in liddriven cavity, Int. Commun. Heat Mass Transfer, 37 (2010) 15281534. ##[28] E. AbuNadaa, A.J. Chamkhac: Mixed convection flow in a liddriven inclined square enclosure filled with a nanofluid, Eur. J. Mech. B/Fluids, 29 (2010) 472482. ##[29] F. Talebi, A.H. Mahmoudi, M. Shahi: Numerical study of mixed convection flows in a square liddriven cavity utilizing nanofluid, Int. Commun. Heat Mass Transfer, 37 (2010) 7990. ##[30] J. Sabbaghzadeh and S. Ebrahimi: Effective of thermal conductivity of nanofluids containing cylindrical nanoparticles, Int. J. of Nanosci., 6 (2007) 4549. ##[31] N. Masoumi, N. Sohrabi and A. Behzadmehr, A new model for calculating the effective viscosity of nanofluids, J. Phys. D: Appl. Phys., 42 (2009) 055501 (6pp). ##[32] Y. He, C. Qi, Y. Hu, B. Qin, Y. Ding: Lattice Boltzmann simulation of aluminawater nanofluid in a square cavity, Nanoscale Research Letters, 6 (2011) 184192. ##[33] Y. Xuan , W. Roetzel: Conceptions for heat transfer correlation of nanofluids, Int. J. Heat Mass Transfer, 43 (19) (2000) 37013707. ##[34] R. Prasher, E.P. Phelan: Brownian motion based convectiveconductive model for the effective thermal conductivity of nanofluids, ASME J. Heat Transfer, 128 (2006) 588593. ##[35] Y. Ding, H. Alias, D. Wen, R. A. Williams: Heat transfer of aqueous suspensions of carbon nanotubes (CNT nanofluids), Int. J. Heat and Mass Transfer, 49 (2006) 240250. ##[36] A. Einstein: Investigations on the Theory of the Brownian movement, Dover, New York, (1959), p. 64. ##[37] M. K. Moallemi, K.S. Jang: Prandtl number effects on laminar mixed convection heat transfer in a liddriven cavity, Int. J. Heat Mass Transfer, 35 (1992) 18811892.##]
Numerical Study of HydroMagnetic Nanofluid Mixed Convection in a Square LidDriven Cavity Heated From Top and Cooled From Bottom
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In the present research mixed convection flow through a copperwater nanofluid in a driven cavity in the presence of magnetic field is investigated numerically. The cavity is heated from top and cooled from bottom while its two vertical walls are insulated. The governing equations including continuity, NS and energy equations are solved over a staggered grid system. The study is conducted for Grashof number103 to 105, Hartmann number 0 to 100 and volume fraction number 0 to 5% while Reynolds number is fixed at 100. Hamilton–Crosser and Brinkman models have estimated effective thermal conductivity and effective viscosity of nanofluid, respectively. It is observed that magnetic field has unconstructive effect on heat transfer process whereas nanoparticles increase heat transfer rate.
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29
42


A.
Zare Ghadi
Mechanical Engineering Department, University of Semnan ,Semnan, I.R. Iran
Mechanical Engineering Department, University
Iran


M.
Sadegh Valipour
Mechanical Engineering Department, University of Semnan ,Semnan, I.R. Iran
Mechanical Engineering Department, University
Iran
LidDriven Cavity
MHD Flow
Mixed convection
Nanofluid
[[1] B. Gebhart, L. Pera: The nature of vertical natural convection flows resulting from the combined buoyancy effects of thermal and mass diffusion, Int. J. Heat and Mass Transfer. 14 (1971) 20252050. ##[2] A. Bejan: Mass and heat transfer by natural convection in a cavity, Int. J. Heat Fluid Flow. 6(3) (1985) 21252150. ##[3] C. Beghein, F. Haghighat, F. Allard: Numerical study of doublediffusive natural convection in a square cavity, Int. J. Heat Mass Transf. 35 (1992) 833846. ##[4] A.J. Chamkha, H. AlNaser: Hydro magnetic doublediffusive convection in a rectangular enclosure with opposing temperature and concentration gradients, Int. J. Heat Mass Transf. 45 (2002) 24652483. ##[5] Q.H. Deng, J. Zhou, C.Mei, Y.M. Shen: Fluid, heat and contaminant transport structures of laminar doublediffusive mixed convection in a twodimensional ventilated enclosure, Int. J. Heat Mass Transf. 47(24) (2004) 52575269. ##[6] A. M. AlAmiri, Kh. M. Khanafer, I. Pop: Numerical simulation of combined thermal and mass transport in a square liddriven cavity, Int. J. Therm. Sci. 46(7) (2007) 662671. ##[7] B. B. Beya, T. Lili: Oscillatory doublediffusive mixed convection in a twodimensional ventilated enclosure, Int. J. Heat Mass Transf. 50(2324) (2007) 45404553. ##[8] M. A. Teamah, W. M. ElMaghlany: Numerical simulation of doublediffusive mixed convective flow in rectangular enclosure with insulated moving lid, Int. J. Therm. Sci. 49(9) (2010) 16251638. ##[9] F. Talebi, A. H. Mahmoudi, M. Shahi: Numerical study of mixed convection flows in a square liddriven cavity utilizing nanofluid, Int. Commun. Heat Mass Transf. 37(1) (2010) 7990. ##[10] H. Nemati, M. Farhadi, K. Sedighi, E. Fattahi, A.A.R. Darzi: Lattice Boltzmann simulation of nanofluid in liddriven cavity, Int. Commun. Heat Mass Transf. 37(10) (2010) 15281534. ##[11] A. J. Chamkha, E. AbuNada: Mixed convection flow in single and doublelid driven square cavities filled with waterAl2O3 nanofluid: Effect of viscosity models, Europ. J. Mech. B/Fluids. Available online 19 March 2012. ##[12] F. Talebi, A.H. Mahmoudi, M. Shahi, Numerical study of mixed convection flows in a square liddriven cavity utilizing nanofluid, International Communications in Heat and Mass Transfer 37 (2010) 79–90. ##[13] E. AbuNada, A.J. Chamkha, Mixed convection flow in a liddriven inclined square enclosure filled with a nanofluid, European Journal of Mechanics  B/Fluids (29) (2010) 472482. ##[14] M.A.A. Hamad, I. Pop, A.I. Md Ismail, Magnetic field effects on free convection flow of a nanofluid past a vertical semiinfinite flat plate, Nonlinear Analysis: Real World Applications 12 (2011) 1338–1346. ##[15] M.A.A. Hamad, Analytical solution of natural convection flow of a nanofluid over a linearly stretching sheet in the presence of magnetic field, International Communications in Heat and Mass Transfer 38 (2011) 487–492. ##[16] B. Ghasemi, S.M. Aminossadati, A. Raisi, Magnetic field effect on natural convection in a nanofluidfilled square enclosure, International Journal of Thermal Sciences 50 (2011) 17481756. ##[17] R.C.D. Cruz, J. Reinshagen, R. Oberacker, A.M. Segadaes, M.J. Hoffmann, Electrical Conductivity and stability of concentrated aqueous alumina suspensions, Journal of Colloid and Interface Science 286 (2005) 579–588. ##[18] H.C. Brinkman, The viscosity of concentrated suspensions and solutions, The Journal of Chemical Physics 20 (1952) 571–581. ##[19] H.E. Patel, T. Pradeep, T. Sundararajan, A. Dasgupta, N. Dasgupta, S.K. Das, A microconvection model for thermal conductivity of nanofluid, pramana journal of physics 65 (2005) 863–869. ##[20] S.V. Patankar, Numerical Heat Transfer and Fluid Flow, Hemisphere Publisher, New York, NY, 1980. ##[21] H.K. Versteeg, W. Malalasekera, An introduction to computational fluid dynamics. The finite volume method, John Wiley & Sons Inc, New York, 1995.##]
Investigation of Activation Time on Pore Size Distribution of Activated Carbon Determined with Different Methods
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2
Three activated carbons are synthesized in a rotary reactor at different activation times. The adsorption isotherms of the samples are measured The pore size distribution of the samples is determined using combined Saito and Foley method, BJH method. An average potential function has been determined inside the cylindrical pores. The effect of activation time on the pore size distribution samples was investigated. In the micropore size range, as the reaction started, the SF method show the initial micropore was generated. As the activation reaction progress, the micropore volume is developed and widened and therefore area under the PSD curve is increased. Improving the reaction, the pore overlapping was carried out and this occurrence causes decreasing in micropore volume. In the mesopore size range, mesopore volume is increased as the reaction progress. It is acceptable because both developing and overlapping of pores causes improvement of mesopore (and macropore) volume
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43
47


F.
Haghighatju
Chemical Engineering Department, University of Shahid Bahonar, Kerman, I.R. Iran
Chemical Engineering Department, University
Iran


H.
Hashemipour Rafsanjani
Chemical Engineering Department, University of Shahid Bahonar, Kerman, I.R. Iran
Chemical Engineering Department, University
Iran
Activated Carbon
BJH
Micropore
Pore Size Distribution
SF
[[1] P. Klobes, K. Meyer, Porosity and Specific Surface Area Measurements for Solid Materials, National Institute of Standards and Technology, Special Publication (2006) 96017. ##[2] K. Kaneko, Determination of pore size and pore size distribution1. Adsorbents and catalysts, Journal of Membrane Science 96 (1994) 5989. ##[3] M. Jaroniec, J. Choma, M. Kruk, Assessment of reliability of the Horvath_Kawazoe pore size analysis method using argon adsorption isotherms on ordered mesoporous silicas, J. Colloids and Surfaces A: Physicochem. Eng. Aspects 214 (2003) 263269. ##[4] E.P. Barrett, L.G. Joyner, P.P. Halenda, The Determination of Pore Volume and Area Distributions in Porous Substances. I. Computations from Nitrogen Isotherms, J. Am. Chem. Sot, 73 (1951) 373. ##[5] P. Kowalczyk, A.P. Terzyk, P.A. Gauden, L. Solarz , Numerical analysis of Horvath–Kawazoe equation, J. Computers and Chemistry 26 (2002) 125–130. ##[6] G. Horvath, K. Kawazoe, Method for the calculation of effective pore size distribution in molecular sieve carbon, J. Chem. Eng. Jpn. 16 (1983) 470–475. ##[7] G. Horvath, Energetic interactions in phase and molecular level pore characterization in nanorange, J. Colloids and Surfaces A: Physicochemical and Engineering Aspects 141 (1998) 295–304. ##[8] M. Kruk, M. Jaroniec, Critical Discussion of Simple Adsorption Methods Used to Evaluate the Micropore Size Distribution, J. Adsorption 3 (1997) 209219. ##[9] H. Hashemipour Rafsanjani, Study on synthesis activated carbon from Iranian coal, Ph.D. Thesis, Amir Kabir university of technology, Iran, 2001.##]
Investigation of Heat Transfer Enhancement or Deterioration of Variable Properties Al2O3EGwater Nanofluid in Buoyancy Driven Convection
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2
In this study, the natural convection heat transfer of variable properties Al2O3EGwater nanofluid in a differentially heated rectangular cavity has been investigated numerically. The governing equations, for a Newtonian fluid, have been solved numerically with a finite volume approach. The influences of the pertinent parameters such as Ra in the range of 103107 and volume fraction of nanoparticles from 0 to 0.04 on heat transfer characteristics have been studied. The results verified by making overall comparison with some existing experimental results have shown that for Ra=103, for which conduction heat transfer is dominant, the average Nusselt number increases as volume fraction of nanoparticles increases, but for higher Ra numbers in contradiction with the constant properties cases it decreases. This reduction, which is associated with increased viscosity, is more severe at Ra of 104 compared to higher Ra numbers such that the least deterioration in heat transfer occurs for Ra=107. This is due to the fact that as Ra increases, the Brownian motion enhances; thus conductivity improves and becomes more important than viscosity increase. An scale analysis, performed to clarify the contradictory reports in the literature on the natural convection heat transfer enhancement or deterioration of nanofluids, showed that different kinds of evaluating the base fluid Rayleigh number has led to such a difference.
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48
64


H.
Khorasanizadeh
Department of Thermofluids, Faculty of Mechanical Engineering, University of Kashan, Kashan, I.R. Iran
Department of Thermofluids, Faculty of Mechanical
Iran


M. M.
Fakhari
Department of Thermofluids, Faculty of Mechanical Engineering, University of Kashan, Kashan, I.R. Iran
Department of Thermofluids, Faculty of Mechanical
Iran


S. P.
Ghaffari
Department of Thermofluids, Faculty of Mechanical Engineering, University of Kashan, Kashan, I.R. Iran
Department of Thermofluids, Faculty of Mechanical
Iran
Enclosure
Ethylene Glycol
Nanofluid
Natural Convection
Nusselt Number
Variable properties
[[1] X.Q. Wang, A.S. Mujumdar, Heat transfer characteristics of nanofluids: a review, International Journal of Thermal Science 46 (2007) 119. ##[2] J. Choi, Y. Zhang, Numerical simulation of laminar forced convection heat transfer of Al2O3water nanofluid in a pipe with return bend, International Journal of Thermal Science 55 (2012) 90102. ##[3] P.K. Namburu, D.K. Das, K.M. Tanguturi, R.S. Vajjha, Numerical study of turbulent flow and heat transfer characteristics of nanofluids considering variable properties, International Journal of Thermal Science 48 (2009) 290302. ##[4] R.J. Goldstein, W.E. Ibele, S.V. Patankar, T.W. Simon, T.H. Kuehn, P.J. Strykowski, K.K. Tamma, J.V.R. Heberlein, J.H. Davidson, J. Bischof, F.A. Kulacki, U. Kortshagen, S. Garrick, V. Srinivasan, K. Ghosh, R. Mittal, Heat transferA review of 2005 literature, International Journal of Heat and Mass Transfer 53 (2010) 43974447. ##[5] K. Khanafer, K. Vafai, M. Lightstone, Buoyancydriven heat transfer enhancement in a twodimensional enclosure utilizing nanofluids, International Journal of Heat and Mass Transfer 46 (2003) 36393653. ##[6] K.C. Lin, A. Violi, Natural convection heat transfer of nanofluids in a vertical cavity: Effects of nonuniform particle diameter and temperature on thermal conductivity, International Journal of Heat and Fluid Flow 31 (2010) 236245. ##[7] G.A. Sheikhzadeh, A.Arefmanesh, M.H. Kheirkhah, R. Abdollahi, Natural convection of Cu–water nanofluid in a cavity with partially active side walls, European Journal of Mechanics  B/Fluids 30 (2011) 166176. ##[8] M. Jahanshahi, S.F. Hosseinizadeh, M. Alipanah, A. Dehghani, G.R. Vakilinejad, Numerical simulation of free convection based on experimental measured conductivity in a square cavity using Water/SiO2 nanofluid, International Communications in Heat and Mass Transfer 37 (2010) 687694. ##[9] A.K. Santra, S. Sen, N. Chakraborty, Study of heat transfer characteristics of copperwater nanofluid in a differentially heated square cavity with different viscosity models, Journal of Enhanced Heat Transfer 15 (2008) 273287. ##[10] C.J. Ho, M.W. Chen, Z.W. Li, Numerical simulation of natural convection of nanofluid in a square enclosure: Effects due to uncertainties of viscosity and thermal conductivity, International Journal of Heat and Mass Transfer 51 (2008) 45064516. ##[11] E. AbuNada, Z. Masoud, A. Hijazi, Natural convection heat transfer enhancement in horizontal concentric annuli using nanofluids, International Communications in Heat and Mass Transfer 35 (2008) 657665. ##[12] N. Putra, W. Roetzel, S.K. Das, Natural convection of nanofluids, Heat and Mass Transfer 39 (2003) 775784. ##[13] C.H. Li, G.P. Peterson, Experimental studies of natural convection heat transfer of Al2O3/DI water nanoparticle suspensions (Nanofluids), Advances in Mechanical Engineering (2010) doi:10.1155/2010/742739. ##[14] C.J. Ho, W.K. Liu, Y.S. Chang, C.C. Lin, Natural convection heat transfer of aluminawater nanofluid in vertical square enclosures: An experimental study, International Journal of Thermal Science 49 (2010) 13451353. ##[15] A.G.A. Nnanna, Experimental model of temperaturedriven nanofluid, Journal of Heat Transfer 129 (2007) 697704. ##[16] K. Khanafer, K. Vafai, A critical synthesis of thermophysical characteristics of nanofluids, International Journal of Heat and Mass Transfer 54 (2011) 44104428. ##[17] E. AbuNada, A.J. Chamkha, Effect of nanofluid variable properties on natural convection in enclosures filled with a CuOEGWater nanofluid, International Journal of Thermal Science 49 (2010) 23392352. ##[18] E. AbuNada, Z. Masoud, H.F. Oztop, A. Campo, Effect of nanofluid variable properties on natural convection in enclosures, International Journal of Thermal Science 49 (2010) 479491. ##[19] B.C. Sahoo, R.S. Vajjha, R. Ganguli, G.A. Chukwu, D.K. Das, Determination of rheological behavior of aluminum oxide nanofluid and development of new viscosity correlations, Petroleum Science and Technology 27 (2009) 17571770. ##[20] R.S. Vajjha, D.K. Das, Experimental determination of thermal conductivity of three nanofluids and development of new correlations, International Journal of Heat and Mass Transfer 52 (2009) 46754682. ##[21] R.S. Vajjha, D.K. Das, Specific heat measurement of three nanofluids and development of new correlations, Journal of Heat Transfer 131 (2009) 17. ##[22] R.S. Vajjha, D.K. Das, B.M. Mahagaonkar, Density measurement of different nanofluids and their comparison with theory, Petroleum Science and Technology 27 (2009) 612624. ##[23] B.C. Pak, Y.I. Cho, Hydrodynamic and heat transfer study of dispersed fluids with submicron metallic oxide particles, Experimental Heat Transfer 11 (1999) 151170. ##[24] Y. Xuan, W. Roetzel, Conceptions for heat transfer correlation of nanofluids, International Journal of Heat and Mass Transfer 43 (2000) 37013707. ##[25] H.C. Brinkman, The viscosity of concentrated suspensions and solutions, Journal of Chemical Physics 20 (1952) 571. ##[26] X. Wang, X. Xu, S.U.S. Choi, Thermal conductivity of nanoparticle–fluid mixture, Journal of Thermophysics and Heat Transfer 13 (1999) 474–480. ##[27] ASHRAE Handbook, Fundamentals. American Society of Heating, Refrigerating and AirConditioning Engineers Inc., Atlanta, GA, 2005. ##[28] F.P. Incropera, D.P. DeWitt, Introduction to Heat Transfer, third ed. John Wiley & Sons, Inc., New York, 1996. ##[29] R.S. Vajjha, D.K. Das, D.P. Kulkarni, Development of new correlations for convective heat transfer and friction factor in turbulent regime for nanofluids, International Journal of Heat and Mass Transfer 53 (2010) 46074618. ##[30] S.V. Patankar, Numerical Heat Transfer and Fluid Flow, McGrawHill, 1980. ##[31] D. Wen, Y. Ding, Natural Convective Heat Transfer of Suspensions of Titanium Dioxide Nanoparticles (Nanofluids), IEEE Transactions on Nanotechnology 5 (2006) 220227. ##[32] A. Bejan, Convective Heat Transfer, second ed. John Wiley & Sons, New York, 1995. ##[33] K.S. Hwang, J.H. Lee, S.P. Jang, Buoyancydriven heat transfer of waterbased Al2O3 nanofluids in a rectangular cavity, International Journal of Heat and Mass Transfer 50 (2007) 40034010.##]
Numerical Investigation of Double Diffusive Mixed Convective Flow in a LidDriven Enclosure Filled with Al2O3Water Nanofluid
2
2
Doublediffusive mixed convection in a liddriven square enclosure filled with Al2O3water is numerically investigated. Twodimensional nonlinear governing equations are discretized using the control volume method and hybrid scheme. The equations are solved using SIMPLER algorithm. The results are displayed in the form of streamlines, isotherms, and isoconcentrations when the Richardson number varies between 0.01 and 100, the Lewis number changes from 0.1 to 10, the buoyancy ratio ranges between 0 and 5,the volume fractions of nanoparticles differs from 0 to 0.06 and the source location moves from the top toward bottom of the left wall. Moreover, the variation of average Nusselt and Sherwood number are illustrated. It is observed that heat transfer enhances as nanoparticles volume fraction increases, while mass transfer reduces. Additionally, by increasing the buoyancy ratio, both heat and mass transfer are increased.
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65
77


A.
Fattahi
Mechanical Engineering Department, Iran University of Science and Technology, Narmak, Tehran, I.R. Iran
Mechanical Engineering Department, Iran University
Iran


M.
Alizadeh
Mechanical Engineering Department, Iran University of Science and Technology, Narmak, Tehran, I.R. Iran
Mechanical Engineering Department, Iran University
Iran
Al2O3water nanofluid
Double diffusion
Mixed convection
Variable properties
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Numerical Study of Operating Pressure Effect on Carbon Nanotube Growth Rate and Length Uniformity
2
2
Chemical Vapor Deposition (CVD) is one of the most popular methods for producing Carbon Nanotubes (CNTs). The growth rate of CNTs based on CVD technique is investigated by using a numerical model based on finite volume method. Inlet gas mixture, including xylene as carbon source and mixture of argon and hydrogen as carrier gas enters into a horizontal CVD reactor at atmospheric pressure. In this article the operating pressure variations are studied as the effective parameter on CNT growth rate and length uniformity.
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78
85


B.
Zahed
Mechanical Engineering Department, University of Sistan and Baluchestan, Zahedan, I.R. Iran
Mechanical Engineering Department, University
Iran


T.
Fanaei S.
Electrical and Electronic Department, University of Sistan and Baluchestan, Zahedan, I.R.Iran
Electrical and Electronic Department, University
Iran


A.
Behzadmehr
Mechanical Engineering Department, University of Sistan and Baluchestan, Zahedan, I.R. Iran
Mechanical Engineering Department, University
Iran
behzadmehr@hamoon.usb.ac.ir


H.
Ateshi
Chemical Engineering Department, University of Sistan and Baluchestan, Zahedan, I.R. Iran
Chemical Engineering Department, University
Iran
Carbon Nanotube
Chemical Vapor Deposition
Operating Pressure
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