Dispersions of CuO Nanoparticles in Paraffin Prepared by Ultrasonication: A Potential Coolant Shriram S. Sonawane + , Rohit S. Khedkar, Kailas L. Wasewar and Ajit P. Rathod Department of Chemical Engineering, Visvesvaraya National Institute of Technology (VNIT), Nagpur, Maharashtra (India) Abstract. In this study, CuO nanoparticles of rod shape were synthesized with sol gel method, the thermal conductivity of CuO nanoparticles in paraffin were investigated up to a volume fraction of 7.5 % of particles. The nanofluid was prepared by dispersing CuO nanoparticles in paraffin by using high intensity ultrasonic equipment. The mean diameter and shape of CuO nanoparticles was confirmed with TEM and XRD and it was rod shape 25 nm. While the thermal conductivity of nanofluids has been measured with KD2 pro analyzer based on transient hot wire methods. The effective thermal conductivity of CuO nanoparticles in paraffin was measured at room temperatures The experimental results showed that the thermal conductivity increases with an increase of particle volume fraction, and the enhancement was observed to be 20 % over the base fluid for a nanofluid with 3% volume fraction of CuO nanoparticles. Keywords: Sol Gel method, Engineering suspension, Ultrasonication, Thermal conductivity. 1. Introduction Nanofluids are liquid suspensions of particles with dimensions between 1-100 nm. After the pioneering work of Choi [1], nanofluids become advance heat transfer fluids. Their potential benefits and applications in many industries from electronics to transportation have attracted great interest from many researchers both experimentally and theoretically. Efforts in research in the nanofluids area has increased annually since 1995; and confirmed with related research papers publication in Science Citation Index journals. Few papers [2,3] provide a detailed literature review of nanofluids various parameter including synthesis, potential applications, and experimental and analytical analysis of effective thermal conductivity, effective thermal diffusivity, and convective heat transfer. Published results show an enhancement in the thermal conductivity of nanofluids, in a wide range even for the same host fluid and same nominal size or composition of the additives. Since this enhancement cannot be explained with the existing classical effective thermal-conductivity models, such as the Maxwell [4] or Hamilton.Crosser [5] models, this also motivates a wide range of theoretical approaches for modelling these thermal phenomena. Reported results show that the particle volume concentration, particle material, particle size, particle shape, base fluid material, temperature, additive, and acidity play an important role in enhancement of the thermal conductivity of nanofluids. Masuda et al. [6] first presented the effect of the fluid temperature on the effective thermal conductivity of nanoparticle suspensions. They reported that for water-based nanofluids, consisting of SiO 2 and TiO 2 nanoparticles, the thermal conductivity was not much more temperature dependent than that of the base fluid. Contrary to this result, Das et al. [7] observed a two-to-four fold increase in the thermal conductivity of nanofluids, containing Al 2 O 3 and CuO nanoparticles in water, over a temperature range of 21 0 C to 51 0 C. Several groups [8, 9] reported studies with different nanofluids, which support the result of Das et al. [7]. For the temperature dependence of the relative thermal conductivity (ratio of effective thermal conductivity of + Corresponding author. Tel.: + (0712-2801562); fax: +(712-2223230). E-mail address: (shriramsonawane@gmail.com). 2012 3rd International Conference on Biology, Environment and Chemistry IPCBEE vol.46 (2012) © (2012) IACSIT Press, Singapore DOI: 10.7763/IPCBEE. 2012. V46. 11 48