Numerical investigation on effect of base fluids and hybrid nanofluid in forced convective heat transfer M. Nuim Labib a, * , Md. J. Nine a , Handry Afrianto a , Hanshik Chung b , Hyomin Jeong b a Department of Energy and Mechanical Engineering, Gyeongsang National University, Cheondaegukchi-Gil 38, Tongyeong 650-160, Gyeongnam, South Korea b Department of Energy and Mechanical Engineering, Gyeongsang National University, Institute of Marine Industry, Cheondaegukchi-Gil 38, Tongyeong 650-160, Gyeongnam, South Korea article info Article history: Received 11 November 2011 Received in revised form 30 March 2013 Accepted 4 April 2013 Available online xxx Keywords: CFD Two-phase model Hybrid/combined nanofluids Non-Newtonian fluid CNTs abstract Two-phase mixture model has been chosen to study forced convective heat transfer of nanofluid introducing a new concept of heat transfer enhancement in this article. Two different base fluids are individually employed to investigate the effect of base fluids on convective heat transfer mixing Al 2 O 3 nanoparticles. The computational method has been successfully validated in case of Al 2 O 3 /water Nanofluids using available experimental data reported in the literature. The results show that Ethylene Glycol base fluid gives better heat transfer enhancement than that of water. Mixture of Al 2 O 3 nano- particles into CNTs/water Nanofluids is considered as a new concept of combined/hybrid nanofluids that can successfully enhance convective heat transfer. The computational model for CNTs/water nanofluid has been validated comparing the results with experimental data reported in literature. Then the vali- dated method was used to simulate new concept of combined nanofluids. Combination of CNTs and Al 2 O 3 nanoparticles into water base fluid tends to enhance the convective heat transfer performance significantly. It happens because CNTs nanofluid shows higher shear thinning behavior which causes the boundary layer thinner; in these regions the significant convective heat transfer enhancement takes place. Ó 2013 Elsevier Masson SAS. All rights reserved. 1. Introduction The heat transfer properties of thermo fluid play an important role in the development of energy-efficient heat transfer equip- ment. Passive enhancement methods are commonly utilized in the heat exchangers and electronics devices. But the conventional working fluids such as ethylene glycol, water and engine oil have poor heat transfer properties. In this regard, the development of advanced heat transfer fluids with higher heat transfer properties is in a strong demand. There has been serious effort to overcome this problem since Maxwell [1] investigated the possibility of increasing the thermal performance of conventional heat transfer fluid by adding particles. Maxwell’s study showed that the conductivity of liquidesolid mixtures improves with increasing particle volume fraction. In 1993, Masuda et al. [2] studied the heat transfer performance of liquid with solid nanoparticles suspension. In 1995, Choi [3] introduced the term of “nanofluids” and successively gained the nanofluids becoming more familiar in term of heat transfer enhancement. Because of the extensively greater thermal conduc- tivity and heat transfer performance of nanofluids compared to the base fluids and expected to be more relevant and efficient for practical applications. Wen and Ding [4] focused on the entry region under laminar flow condition using Al 2 O 3 /water nanofluids. They showed that enhancement increases with Reynolds number as well as volume concentration of nanoparticles. Heris et al. [5,6] investigated the convective heat transfer coefficient of Al 2 O 3 /water and CuO/water nanofluids for laminar flow in annular tube under a constant wall temperature boundary condition. Lotfi et al. [7] have compared the single-phase with the Mixture and Eulerian two-phase models for the forced convection flow of Al 2 O 3 /water nanofluid with tempera- ture independent properties. Specifically, they have compared the Nusselt number predictions for a 1% volume fraction of nanoparticles with several correlations and one set of experimental values. They have also considered the effect of volume concentration on the wall temperature. They concluded that the Mixture model is more precise than the other two models. Xuan and Li [8] explained that the two- phase approach seems a better model to describe the nanofluid flow. In fact, the slip velocity between the fluid and particles might be * Corresponding author. E-mail address: mnuim.labib@pertamina.com (M. Nuim Labib). 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 2013 Elsevier Masson SAS. All rights reserved. http://dx.doi.org/10.1016/j.ijthermalsci.2013.04.003 International Journal of Thermal Sciences xxx (2013) 1e9 Please cite this article in press as: M. Nuim Labib, et al., Numerical investigation on effect of base fluids and hybrid nanofluid in forced convective heat transfer, International Journal of Thermal Sciences (2013), http://dx.doi.org/10.1016/j.ijthermalsci.2013.04.003