Hydromagnetic slip flow of water based nanofluids past a wedge with convective surface in the presence of heat generation (or) absorption M.M. Rahman * , M.A. Al-Lawatia, I.A. Eltayeb, N. Al-Salti Department of Mathematics and Statistics, College of Science, Sultan Qaboos University, P.O. Box 36, P.C.123 Al-Khod, Muscat, Oman article info Article history: Received 9 July 2011 Received in revised form 4 December 2011 Accepted 15 February 2012 Available online 21 March 2012 Keywords: Nanofluid Wedge Slip flow Convective surface Similarity solution Free convection abstract Heat transfer characteristics of a two-dimensional steady hydromagnetic slip flow of water based nanofluids (TiO 2 ewater, Al 2 O 3 ewater, and Cuewater) over a wedge with convective surface taking into account the effects of heat generation (or absorption) has been investigated numerically. The local similarity solutions are obtained by using very robust computer algebra software MATLAB and presented graphically as well as in a tabular form. The results show that nanofluid velocity is lower than the velocity of the base fluid and the existence of the nanofluid leads to the thinning of the hydrodynamic boundary layer. The rate of shear stress is significantly influenced by the surface convection parameter and the slip parameter. It is higher for nanofluids than the base fluid. The results also show that within the boundary layer the temperature of the nanofluid is higher than the temperature of the base fluid. The rate of heat transfer is found to increase with the increase of the surface convection and the slip parameters. Addition of nanoparticles to the base fluid induces the rate of heat transfer. The rate of heat transfer in the Cuewater nanofluid is found to be higher than the rate of heat transfer in the TiO 2 ewater and Al 2 O 3 ewater nanofluids. Ó 2012 Elsevier Masson SAS. All rights reserved. 1. Introduction A base fluid (water, engine oil, ethylene glycol etc) containing suspension of ultra fine metallic (for example Cu, Al, Fe, Hg, Ti etc) or a non-metallic (for example Al 2 O 3 , CuO, SiO 2 , TiO 2 ) nanometer- sized (usually less than 100 nm) solid particles or fibers is termed nanofluid (Choi [1]). The main characteristics of this fluid are the significant enhancement of the thermal properties of the base fluid; minimal clogging in flow passage; long term stability and homo- geneity compared to those fluids containing micro- or milli-sized particles (see Masuda et al. [2], Lee et al. [3], Xuan and Li [4], and Xuan and Roetzel [5]). Thus, nanofluids appear to be a very inter- esting alternative for advanced thermal applications, in particular micro-scale and nano-scale heat transfer. Due to the better performance of heat exchange, great potentials and features; nanofluids can be utilized in several industrial applications as in transportation, chemical production, production of microelec- tronics, automotives, power generation in a power plant, advanced nuclear systems (Buongiorno [6]), and nano-drug delivery (Klein- streuer et al. [7]). Because of the wide range of applications of nanofluids in macro/micro devices significant research has been carried out in recent years to study heat transfer characteristics of these fluids. A recent review on this subject by Kakac and Pra- muanjaroenkij [8] provide excellent information on convective heat transfer enhancement with nanofluids. Recent advances in nanotechnology have allowed researchers to study the next-generation heat transfer nanofluids. The past decade has seen increasing research activities in heat intensifica- tion using nanofluids. Eastman et al. [9] noticed 40% increase in thermal conductivity using 0.3% of pure Cu nanoparticles of sized less than 10 nm dispersed in ethylene glycol. Murshed et al. [10] noticed 33% enhancement of thermal conductivity for 5% volume fraction of TiO 2 dispersed in pure water. Many researchers have studied and reported results on convective heat transfer in nano- fluids considering various flow conditions in different geometries. See, e.g., Khanafer et al. [11], Maiga et al. [12], Jou and Tzeng [13], Hwang et al. [14], Tiwari and Das [15], Oztop and Abu-Nada [16], Abu-Nada and Oztop [17], Muthtamilselvan et al. [18]. Excellent reviews on nanofluids have been done by Das et al. [19], and Wang and Mujumdar [20e22]. Kuznetsov and Nield [23] studied the natural convection boundary layer flow of a nanofluid past a vertical plate while Nield and Kuznetsov [24] studied a double- diffusive natural convection boundary layer flow along a vertical plate embedded in a porous medium saturated by a nanofluid. In both studies they applied Buongiorno [6] nanofluid model which includes Brownian diffusion and thermophoresis and investigated * Corresponding author. Fax: þ968 2414 1490. E-mail address: mansurdu@yahoo.com (M.M. Rahman). Contents lists available at SciVerse ScienceDirect International Journal of Thermal Sciences journal homepage: www.elsevier.com/locate/ijts 1290-0729/$ e see front matter Ó 2012 Elsevier Masson SAS. All rights reserved. doi:10.1016/j.ijthermalsci.2012.02.016 International Journal of Thermal Sciences 57 (2012) 172e182