Nanofluid flow and heat transfer around a circular cylinder: A study on effects of uncertainties in effective properties

Abstract

Nanofluids are considered to be the coolants of future; in the interest of their enhanced thermal conductivity. But, the dilemma in prediction of their effective properties is a major problem in assessing their real heat transfer potential. A numerical analysis of flow and heat transfer from a hot circular cylinder exposed to an uniform stream of nanofluid has been performed to showcase the effects of uncertainties in effective properties of nanofluids. Water based nanofluids with ultra-fine Titania (TiO2) nanoparticles with the particle volume fraction varying from 0% to 2% have been considered. A steady, laminar, 2-D flow with forced convective heat transfer has been taken into account in the Reynolds number range of 1 ≤ Re ≤ 40. Finite-volume method based on SIMPLE algorithm is used to solve the governing equations. Three cases of analysis have been carried out in which the thermal conductivity and viscosity of nanofluids are determined using two sets of theoretical models and one set of experimental thermal conductivity and viscosity data from literature, respectively. Flow and heat transfer characteristics of nanofluids are found to be dependent on particle volume fraction and Reynolds number. Enhanced drag, altered wake lengths, modified flow separation and higher heat transfer rates are seen in nanofluids. But, a comparative scrutiny of the three cases; apparently shows that the flow and heat transfer characteristics differ both quantitatively and qualitatively between each case. This work promulgates the importance of a precise effective thermal conductivity and viscosity models for nanofluids to promote the real time application of nanofluids in developing high efficiency heat transfer systems. © 2016 Elsevier B.V.