Theoretical and Experimental Investigations on Nanofluids for Their Fluid Dynamics and Heat Transfer Behaviors

摘要

As a first part of this paper an analytical study is presented for heat transfer by nanofluids using heat transfer correlations for laminar as well as turbulent flows available in the current literature. This study shows an increase of 50% in convective heat transfer coefficient in laminar regime and about 2.2 times in turbulent regime due to the addition of 10% copper oxide nanoparticles in water. It is also observed that in turbulent regime beyond 30% of copper oxide nanoparticles concentration, the heat transfer coefficient begins to diminish as predicted by the correlations presented in published papers. In the second part of the paper, modeling studies have been presented for two dimensional flows using the well-known computational fluid dynamics software Fluent (2005) where the nanofluid is treated as a homogeneous fluid with special thermal properties, e.g. Viscosity, density, specific heat and thermal conductivity computed from new correlations available for nanofluids. These values differ substantially from the pure liquid phase and are dependent on the nanoparticle volume fraction. Fluent results show an increase of 45% in convective heat transfer coefficient in laminar regime for 10% particle concentration of copper oxide in water. Finally, to verify the theoretical studies an experimental apparatus has been built to measure the frictional head loss and the convective heat transfer coefficients of various types of nanofluids. This apparatus and its function to determine fluid dynamic and thermal characteristics of nanofluids to corroborate the theoretical findings are described in this paper.