International Scientific Journal

Thermal Science - Online First

online first only

Numerical simulation of flow reversal at high Rayleigh number in a vertical square duct - an application of the spectral method

In this paper we numerically study the mixed convection in hydrodynamically as well as thermally developed incompressible laminar flow of nanofluids in a vertical square duct subject to the thermal boundary condition of constant heat flux per unit axial length with constant peripheral temperature at any cross section, using the spectral method and the finite difference method. We have considered three different water-based nanofluids containing Alumina, Titanium Oxide or Silver nanoparticles. We observe that the Rayleigh number remarkably reduces the fluid velocity and even the flow reversal may occur while developing an equi-temperature region for a small region in the centre of the duct. It has also been noted that, for Siler-water nanofluid, the nanoparticle volume fraction increases the Nusselt number more rapidly while slowly decreasing the fRe.
PAPER REVISED: 2017-05-31
PAPER ACCEPTED: 2017-06-12
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