On the anomalous laminar heat transfer intensification in developing region of nanofluid flow in channels or tubes

Abstract

The present work theoretically addresses the experimental observations of nanofluid flow exhibiting highly intensified laminar heat transfer rates at the leading edge of channels or tubes. The basis for this study is the continuum conservation equations for nanofluids. The Rayleigh–Stokes approximation is applied to the nonlinear advective effects and a perturbation scheme, in ascending powers of the nanoparticle volume fraction, is applied. The disparate thicknesses of momentum, heat and volume fraction is exploited to advantage in securing analytical, similar solutions. The volume fraction layer is ‘infinitely’ thin in that its effect on the momentum and thermal transport is essentially its bulk value far from the wall. The composite resulting zeroth- and first-order perturbations show that an increasing modification in the velocity and temperature profiles occur with increasing volume fraction and that this is caused, and quantitatively assessed, by inertial effects of advection and enhanced nanofluid transport properties. Some satisfactory explanations of experiments are made for aluminium oxide nanoparticles in water, in terms of the ratio of nanofluid to base fluid heat transfer coefficients, local heat transfer coefficient and the Nusselt number.