Australian Journal of Basic and Applied Sciences, 4(8): 3780-3793, 2010 ISSN 1991-8178 Corresponding Author: W. Mahmood Mat Yunus, Faris Mohammed Ali, Department of Physics, Faculty of Science, University Putra Malaysia. E-mail: wmmyunus@gmail.com , fawal2003@yahoo.com 3780 Measurement Thermal Conductivity and Thermal Diffusivity of Chromium Nanofluids Faris Mohammed Ali, W. Mahmood Mat Yunus, Mohd Maarof Moksin, Zainal Abidin Talib Department of Physics, Faculty of Science, University Putra Malaysia, 43400 UPM, Serdang, Selangor, Malaysia Abstract: In this study, nanofluids of Chromium (Cr) in water, Ethylene Glycol and Ethanol have been prepared using single step method. The thermal conductivity and diffusivity of these nanofluids were measured via hot wire-photothermal deflection technique. Based on finite difference method (FDM) temperature distribution and photothermal deflection caused by the hot wire inside nanofluids was obtained. A numerical simulation of the heat conduction equation and probe beam deflection has been performed to determine the thermal conductivity and diffusivity of the nanofluids. By fitting the experimental data to the numerical simulation curve the thermal diffusivity and thermal conductivity of Chromium (Cr) in water, Ethylene Glycol and Ethanol were obtained. It is found that thermal conductivity and thermal diffusivity of Cr nanofluids in water, EG and Ethanol are higher than thermal conductivity and thermal diffusivity of respective base fluids. Key words: Chromium nanofluids, Thermal conductivity, Thermal diffusivity INTRODUCTION Nanotechnology is defined as fabrication of devices with atomic or molecular scale precision. Devices with minimum size less than 100 nm become the important products of nanotechnology (Eugene A. Avallone, 2007). Nanotechnology can be defined a system that consist of individual atoms or molecules in submicron dimensions (Bharat Bhushan, 2004). The discovery of novel materials, phenomena, and processes at the nano-scales are the evolution of new theoretical and experimental techniques for the evolution of nanosystems and nano- structures materials. Nanosystems are expected to find various unique applications. The nanotechnology is expected to open new branch in science and technology (Iwao Fujimasa, 1996). In the development of energy-efficient heat transfer equipment, the thermal conductivity of the heat transfer fluid plays a vital role. However traditional heat transfers fluids such as water, oil, and ethylene glycol mixtures are inherently poor heat transfer fluids. With increasing global competition, industries have a strong need to develop advanced heat transfer fluids with significantly higher thermal conductivity and thermal diffusivity of base fluids are presently available (Lee, S. and S.U.S. Choi, 1996). However, metal nanofluids are the good candidates for this purpose. A nanofluid is a fluid with particles size of solids suspension less than hundred nanometer. By introducing nanoparticles into the base fluid, thermal conductivity and thermal diffusivity of the system increased effectively (Wang, X., 1999). A novel expression for the thermal conductivity of nanofluids was proposed by Jung Yeul et al. (2009) which is incorporates the kinetic theory to describe the contribution of the Brownian motion of the nanoparticles. The instantaneous temperature-dependent thermal conductivity using cross sectional infrared microscopy and tracks the effects of aggregation and diffusion over a period of time have been studied by Gharagozloo et al. (2008). The measurements of both the temporal and spatial variations of the thermal conductivity of nanofluids are subjected to a temperature gradient. The thermal conductivity and viscosity of copper nanoparticles in ethylene glycol were investigated by Garg J. et al. (2008). Thermal conductivity of the nanofluid was measured using the transient hot wire method and the viscosity of the nanofluid was measured using a TA instruments AR-G2 rheometer equipped with a 6 cm 1° cone rheometer. Dong-Wook Oh et al. (2008) have studied the application of the 3-omega (3) method for measuring thermal conductivity of nanofluids. The thermal modeling of the 3 device and nanofluid system is conducted based on the modified boundary mismatch assumption proposed by Chen et al. (2004), the effective thermal conductivity of Al2O3