## THERMAL SCIENCE

International Scientific Journal

### Thermal Science - Online First

online first only
### Radiation and heat generation effects in MHD mixed convection flow of nanofluids

**ABSTRACT**

Radiation and heat generation effects in unsteady magnetohydrodynamic (MHD) mixed convection flow of nanofluids along a vertical channel are investigated. Silver ()Ag nanoparticles of spherical shapes and of different sizes in water as a convectional base fluid are incorporated. The purpose of this study is to measure the effect of different sizes of nanoparticles on velocity and temperature. Keeping in mind the size, particle material, shape, clustering and Brownian motion of nanoparticles, Koo and Kleinstreuer model is used. The problem is modelled in terms of partial differential equations with physical boundary conditions. Analytical solutions are obtained for velocity and temperature, plotted and discussed. It is concluded that increasing the size of Ag nanoparticles (up to specific size (30 nm ) results in a very small velocity increment while for large particle size (30 nm -100nm ), no change in velocity is observed. As the small size of nanoparticles has the highest thermal conductivity and viscosity. This change in velocity with size of nanoparticles is found only in water-based nano fluids with low volume fraction 0.01 while at low volume concentration, no change is observed.

**KEYWORDS**

PAPER SUBMITTED: 2015-07-30

PAPER REVISED: 2016-01-15

PAPER ACCEPTED: 2016-02-26

PUBLISHED ONLINE: 2016-03-12

- Maxwell, J.C., A treatise on electricity and magnetism, Clarendon Press series. 1873, Oxford: Clarendon Press. 2 v.
- Hamilton, R. and O. Crosser, Thermal conductivity of heterogeneous two-component systems. Industrial & Engineering chemistry fundamentals, 1, 1962, 3. pp. 187-191.
- Choi, S., Enhancing thermal conductivity of fluids with nanoparticles, ASME-Publications-Fed, 231, 1995, p p. 99-106.
- Sheikholeslami, M., et al., Simulation of MHD CuO-water nanofluid flow and convective heat transfer considering Lorentz forces, Journal of Magnetism and Magnetic Materials, 369, 2014, pp. 69-80.
- Mohyud-Din, S.T., et al., Magnetohydrodynamic Flow and Heat Transfer of Nanofluids in Stretchable Convergent/Divergent Channels, Applied Sciences, 5, 2015, 4, pp. 1639-1664.
- Al-Salem, K., et al., Effects of moving lid direction on MHD mixed convection in a linearly heated cavity, International Journal of Heat and Mass Transfer, 55, 2012, 4, pp. 1103-1112.
- Yu, W. and S. Choi, The role of interfacial layers in the enhanced thermal conductivity of nanofluids: a renovated Maxwell model, Journal of Nanoparticle Research, 5, 2003, 1-2, pp. 167-171.
- Yu, W. and S. Choi, The role of interfacial layers in the enhanced thermal conductivity of nanofluids: a renovated Hamilton-Crosser model, Journal of Nanoparticle Research, 6, 2004, 4, pp. 355-361.
- Xuan, Y., et al., Aggregation structure and thermal conductivity of nanofluids, AIChE Journal, 49, 2003, 4, pp. 1038-1043.
- Koo, J. and C. Kleinstreuer, A new thermal conductivity model for nanofluids, Journal of Nanoparticle Research, 6, 2004, 6, pp. 577-588.
- Das, S.K., et al., Temperature dependence of thermal conductivity enhancement for nanofluids, Journal of Heat Transfer, 125, 2003, 4, pp. 567-574.
- Chon, C.H., et al., Empirical correlation finding the role of temperature and particle size for nanofluid (Al2O3) thermal conductivity enhancement, Applied Physics Letters, 87, 2005, 15, pp. 153107-153107.
- Qasim, M., et al., Mhd boundary layer slip flow and heat transfer of ferrofluid along a stretching cylinder with prescribed heat flux, PloS one, 9, 2014,1.
- Khan, Z.H., et al., MHD stagnation point ferrofluid flow and heat transfer toward a stretching sheet. Nanotechnology, IEEE Transactions on, 13, 2014, 1, pp. 35-40.
- Sheikholeslami, M. and D.D. Ganji, Ferrohydrodynamic and magnetohydrodynamic effects on ferrofluid flow and convective heat transfer, Energy, 75, 2014, pp. 400-410.
- Turkyilmazoglu, M., Unsteady convection flow of some nanofluids past a moving vertical flat plate with heat transfer, Journal of Heat Transfer, 136, 2014, 3, pp. 031704.
- Asma, K., et al., Exact solutions for free convection flow of nanofluids, with ramped wall temperature, The European Physical Journal Plus, 130, 2015, pp. 57-71.
- Tiwari, A.K., et al., Investigation of thermal conductivity and viscosity of Nanoflurids, J. Environ. Res. Develop, 7, 2012, 2, pp. 768-777.
- Zeeshan, A., et al., Magnetohydrodynamic flow of water/ethylene glycol based nanofluids with natural convection through a porous medium, The European Physical Journal Plus, 129, 2014, 12, pp. 1-10.
- Akbar, N.S., et al., Impulsion of induced magnetic field for Brownian motion of nanoparticles in peristalsis, Applied Nanoscience, 2015, pp. 1-12.
- Das, S., Jana, R. N., Natural convective magneto-nanofluid flow and radiative heat transfer past a moving vertical plate, Alexandria Engineering Journal, 54, 2015, pp. 55-64.
- Garoosi, F., et al., Two phase simulation of natural convection and mixed convection of the nanofluid in a squarecavity, Powder Technology, 275, 2015, pp. 239-256.
- Sheikholeslami, M. and M. Rashidi, Ferrofluid heat transfer treatment in the presence of variable magnetic field, The European Physical Journal Plus, 130, 2015, 6, pp. 1-12.
- Patel, H.E., et al., Thermal conductivities of naked and monolayer protected metal nanoparticle based nanofluids: Manifestation of anomalous enhancement and chemical effects, Applied Physics Letters, 83, 2003, 14, pp. 2931-2933.
- Brinkman, H., The viscosity of concentrated suspensions and solutions, The Journal of Chemical Physics, 20, 1952, 4, pp. 571-571.
- Khan, U., et al., Thermo-diffusion, diffusion-thermo and chemical reaction effects on MHD flow of viscous fluid in divergent and convergent channels, Chemical Engineering Science, 141, 2016, pp. 17-27.
- Ahmed, N., et al., MHD flow of an incompressible fluid through porous medium between dilating and squeezing permeable walls, Journal of Porous Media, 17, 2014, 10.
- Sheikholeslami, M. and R. Ellahi, Three dimensional mesoscopic simulation of magnetic field effect on natural convection of nanofluid, International Journal of Heat and Mass Transfer, 89, 2015, pp. 799-808.
- Mohyud-Din, S.T., et al., On heat and mass transfer analysis for the flow of a nanofluid between rotating parallel plates, Aerospace Science and Technology, 46, 2015, pp. 514-522.
- Khan, U., et al., Thermo-diffusion effects on MHD stagnation point flow towards a stretching sheet in a nanofluid, Propulsion and Power Research, 3, 2014, 3, pp. 151-158.
- Jha, B. K., et al., Natural Convection Flow of Heat Generating/Absorbing Fluid near a Vertical Plate with Ramped Temperature, Journal of Encapsulation and Adsorption Sciences, 2, 2012, pp. 61-68.
- Makinde, O. D., Mhone, P. Y., Heat transfer to MHD oscillatory flow in a channel filled with porous medium, Romanian Journal of Physics, 50, 2005, pp. 931-938.
- Said, Z., et al., Mixed convection heat transfer of nanofluids in a lid driven square cavity: A parametric study, International Journal of Mechanical and Materials Engineering (IJMME), 8, 2013, 1, pp. 48-57.