Modelling the Impacts of Shape and Volume Fraction of Nanoparticles on Water Based Nanofluid Flow with Variable Thermophysical Properties

Abstract

In some applications, nano-sized particles are used to enhance heat transfer in thermal energy
systems. Two important practical concerns are the shape of the nanoparticles and the volume
fraction that could lead to optimal performance. This study investigates the effects which the
shape and volume fraction of copper nanoparticles may have on the velocity and temperature
of water based nanofluid. To account for more physical reality, we incorporate the variability
of the viscosity and thermal conductivity. The Hamilton-Crosser’s model of nanofluid thermal
conductivity is also adopted. It is proposed that for a fluid with temperature-dependent
thermo-physical properties, the fluid thermal conductivity in the Hamilton-Crosser’s relation
should be replaced with a constant (temperature-independent) thermal conductivity. The governing
system of nonlinear partial differential equations is solved by using a convergent finite
difference scheme. The results show that increasing the volume fraction decreases the velocity
but increases the temperature, while copper nanoparticles of spherical shape lead to enhanced
temperature than other shapes.