Figure 1 Flow chart for the research methodology of this study
The whole methodology can be simplified into following steps,
- APS – Average particle size has to be determined for particle
aggregation
- Stability – The investigation on stability is a key issue that
influences the properties of nanofluids for application, and it is
necessary to study and analyze influencing factors to the dispersion
stability of nanofluids [45].
- pH Measurement – It determines the nano particle aggregation and
stability of the nanofluid.
- Experimental thermal conductivity and viscosity – Initially thermal
conductivity values are used for degerming the stability of the
nanofluid over a period and once the nanofluid is stable, further
values are taken over various operating conditions.
- Regression analysis – The thermo physical properties values collected
from experimental work and literature work have analyzed and
correlations were formulated.
- Comparison - Experimental results were compared with literature and
regression analysis to validate the correlations formulated.
2.1. Average Particle Size (APS)
of
Nanoparticles
One of the considerations for determining particle aggregation, upon
suspension in the base fluid, involves nano particle size. To evaluate
the solid nano particles’ APS state, various techniques are employed.
Given solid nano particles, techniques that could be employed include
transmission electron microscopy and scanning electron microscopy.
Indeed, the electron microscope does not rely on light as its source of
radiation. Instead, it relies on the electron beam. Figure 2 illustrates
the scanning electron microscopy image for SiO2 nano
particles. To ensure that the nano particles’ APS is assessed, an
appropriate approach becomes the Dynamic Light Scattering technique
[46]. In this technique, the speed of the particle is correlated
with its size, a trend informed by the state of Brownian motion. The
Stokes-Einstein equation illustrating this relation is shown below:
\(D=\ \frac{\text{kT}}{6\pi\mu r}\) (2)