Abstract:
A new generation of heat transfer fluids, nanofluids, can
play a major role in the development of today’s renewable
energies. In the particular case of wind turbines, an undesirable
overheating of electrical and mechanical components can
provoke a noticeable reduction of overall efficiency due to the
temperature is a limiting factor to the electricity generation or
even very expensive repair cost because of an unexpected crash
of generators, or others turbine components. Dispersions of
multiple-layer graphene nanostructures with high thermal
conductivity in conventional working fluids are a promising
type of new heat transfer fluids due to the excellent
performance of nanoadditives in heat transference. Hence,
determining the thermophysical properties of these
nanomaterials under different conditions is the first step and
key issue for analysing and optimizing the dispersions.
Although water-based graphene nanoplatelet nanofluids have
been investigated and some correlations can be found in the
literature, scarce studies were conducted using other industrial
working fluids as base fluids.
The purpose of this study is to carry out a thorough
thermophysical characterization of different loaded samples of
functionalized graphene nanoplatelet dispersions in an
industrial heat transfer fluid, Havoline XLC Pre-mixed 50/50.
Four different nanofluids at mass concentrations (0.25, 0.50,
0.75 and 1.0) wt.% of functionalized graphene nanoplatelets
powder were produced. In order to obtain improved long-term
stabilities, sodium dodecyl benzene sulphonate was added to
the samples at a mass concentration of 0.125 % in relation to
the base fluid without appreciable variations in the pH value.
Stability was assessed through zeta potential and dynamic light
scattering measurements. Tests for determining thermal
conductivity were conducted with a transient hot wire
technique in a wide temperature range. In addition, densities,
dynamic viscosities and specific heat capacities of the samples
were experimentally determined at different temperatures in
order to carry out further studies such as experimental
convective heat transfer coefficients and pressure drops.
Increases in thermal conductivity up to 7.3 % were found with
not very high viscosity rises.
Description:
Papers presented at the 13th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Portoroz, Slovenia on 17-19 July 2017 .
