IJE TRANSACTIONS C: Aspects Vol. 30, No. 12 (December 2017) 1919-1924    Article in Press

PDF URL: http://www.ije.ir/Vol30/No12/C/14-2629.pdf  
downloaded Downloaded: 57   viewed Viewed: 820

A. Shahriari, N. Jahantigh and F. Rakani
( Received: May 26, 2017 – Accepted in Revised Form: September 08, 2017 )

Abstract    The influence of temperature, mean nanoparticle size and the nanoparticle concentration on the dynamic viscosities of nanofluids are investigated in an analytical method followed by introduction of modified equations for calculating the nanofluidsí viscosities. A new correlation is developed for effective viscosity based on the previous model where the Brownian movement of the nanoparticles is considered as the key mechanism. In previous studies, the proposed models were not appropriate for nanoparticles larger than 36 nm. They were also focused on low concentrations of nanoparticles up to 5%. The possibility of homogeneous dispersion of the nanoparticles and the Stokes law are observed here. This new model is explained in terms of temperature, mean nanoparticle diameter, nanoparticle volume concentration and both the nanoparticle and base fluid thermophysical characteristics for the effective viscosity of nanofluids. A combined correction factor is introduced to take into account the simplification for a free stream boundary condition outside the boundary layer. A good agreement is observed between the effective viscosity obtained in this new model and those of recorded experiments conducted for different nanofluids. The results show that the present model is valid for large volume concentration (0% < φ <11%), mean nanoparticle size (13 nm < dp < 95 nm), temperature variations (290 K Normal 0 false false false EN-US X-NONE FA


Keywords    Effective Viscosity: Mean Nanoparticle Diameter: Nanofluid: Thermo physical Properties: Volume Concentration


چکیده    در کار حاضر تأثیر متغیرهای درجه حرارت، اندازه متوسط نانوذره و غلظت نانوذره روی ویسکوزیته دینامیکی نانوسیال بررسی شده است که بر یک روش تحلیلی معادلات اصلاح‌شده ویسکوزیته نانوسالات مبتنی است. مدل جدید بر اساس مدل‌های قبلی که اثر حرکت براونی را به‌عنوان یک پارامتر کلیدی مدنظر قرار می‌دادند، توسعه یافته است. نتایج نشان داد که استفاده از مدل‌های قبلی برای نانوذرات بزرگ‌تر از 36 نانومتر مناسب نیست. هم‌چنین مطالعات قبلی تنها در حجم کسری کم نانوذرات تا 5%متمرکز شده است. در کار حاضر امکان پراکندگی همگن نانوذرات و قانون استوکس برای نانوذرات لحاظ شده است. در مدل جدید اثر دما، قطر متوسط نانوذرات، غلظت نانوذره و نیز ویژگی‌های ترموفیزیکی نانوذره و سیال پایه برای ویسکوزیته مؤثر نانوسیال در نظر گرفته شده است. یک ضریب تصحیح ترکیبی برای لحاظ کردن ساده‌سازی شرط مرزی جریان آزاد در خارج از لایه مرزی معرفی شده است. توافق خوب نتایج بین ویسکوزیته مؤثر به‌دست‌آمده از مدل جدید و نتایج آزمایشگاهی برای نانوسیالات مختلف مشاهده شده است. نتایج نشان می‌دهد که مدل حاضر برای محدوده وسیعی از کسر حجمی (0% < φ <11%)، اندازه متوسط نانوذرات (13 nm < dp < 95 nm)، تغییرات دمایی نانوسیال (290 K < T < 350 K) و انواع مختلفی از نانوذرات معتبر است.


1.      Hannani, S.K., Sadeghipour, M. and Nazaktabar, M., "Natural convection heat transfer from horizontal cylinders in a vertical array confined between parallel walls", International Journal of Engineering,  Vol. 15, No. 3, (2002), 293-302.

2.      Sheikhzadeh, G., Babaei, M., Rahmany, V. and Mehrabian, M., "The effects of an imposed magnetic field on natural convection in a tilted cavity with partially active vertical walls: Numerical approach", International Journal of Engineering-Transactions A: Basics,  Vol. 23, No. 1, (2009), 65-78.

3.      Ziapour, B. and Rahimi, F., "Numerical study of natural convection heat transfer in a horizontal wavy absorber solar collector based on the second law analysis", International Journal of Engineering-Transactions A: Basics,  Vol. 29, No. 1, (2016), 109-117.

4.      Maxwell, J.C., A treatise on electricity end magnetism (1873), clarendon press (1891). 1954, Dover.

5.      Choi, S.U. and Eastman, J.A., Enhancing thermal conductivity of fluids with nanoparticles. 1995, Argonne National Lab., IL (United States).

6.      Ashorynejad, H., Sheikholeslami, M. and Fattahi, E., "Lattice boltzmann simulation of nanofluids natural convection heat transfer in concentric annulus", International Journal of Engineering-Transactions B: Applications,  Vol. 26, No. 8, (2013), 895-904.

7.      Shahriari, A., Jafari, S., Rahnama, M. and Behzadmehr, A., "Effect of nanofluid variable properties on natural convection in a square cavity using lattice boltzmann method", International Review of Mechanical Engineering (IREME),  Vol. 7, No. 3, (2013), 442-452.

8.      Davarnejad, R. and Kheiri, M., "Numerical comparison of turbulent heat transfer and flow characteristics of sio2/water nanofluid within helically corrugated tubes and plain tube", International Journal of Engineering-Transactions A: Basics,  Vol. 28, No. 10, (2015), 1408-1414.

9.      Einstein, A., "Eine neue bestimmung der molekuldimensionen", Annalen der Physik,  Vol. 324, No. 2, (1906), 289-306.

10.    Brinkman, H., "The viscosity of concentrated suspensions and solutions", The Journal of Chemical Physics,  Vol. 20, No. 4, (1952), 571-571.

11.    Lundgren, T.S., "Slow flow through stationary random beds and suspensions of spheres", Journal of Fluid Mechanics,  Vol. 51, No. 2, (1972), 273-299.

12.    Batchelor, G., "The effect of brownian motion on the bulk stress in a suspension of spherical particles", Journal of Fluid Mechanics,  Vol. 83, No. 1, (1977), 97-117.

13.    Chandrasekar, M., Suresh, S. and Bose, A.C., "Experimental investigations and theoretical determination of thermal conductivity and viscosity of Al2O3/water nanofluid", Experimental Thermal and Fluid Science,  Vol. 34, No. 2, (2010), 210-216.

14.    Masoumi, N., Sohrabi, N. and Behzadmehr, A., "A new model for calculating the effective viscosity of nanofluids", Journal of Physics D: Applied Physics,  Vol. 42, No. 5, (2009), 055501.

15.    Khanafer, K., Vafai, K. and Lightstone, M., "Buoyancy-driven heat transfer enhancement in a two-dimensional enclosure utilizing nanofluids", International Journal of Heat and Mass Transfer,  Vol. 46, No. 19, (2003), 3639-3653.

16.    Jang, S.P. and Choi, S.U., "Role of brownian motion in the enhanced thermal conductivity of nanofluids", Applied Physics LetterS,  Vol. 84, No. 21, (2004), 4316-4318.

17.    Prasher, R., Bhattacharya, P. and Phelan, P.E., "Thermal conductivity of nanoscale colloidal solutions (nanofluids)", Physical Review Letters,  Vol. 94, No. 2, (2005), 025901.

18.             Koo, J. and Kleinstreuer, C., "A new thermal conductivity model for nanofluids", Journal of Nanoparticle Research,  Vol. 6, No. 6, (2004), 577-588.

Download PDF 

International Journal of Engineering
E-mail: office@ije.ir
Web Site: http://www.ije.ir