To determine the state of thermal conductivity in relation to the use of
20nm-sizd particles suspended in 60EGW, Sahoo et al. [38] focused on
SiO2 as the selected nanofluids and set their
experimental temperature at 20-90oC. Also, 20% was
set as the experiment’s maximum concentration. Indeed, the state of
enhanced thermal conductivity was reported to be 20%. However, these
results only held when the temperature was 87oC and\(\varnothing=\)10%. It is also worth noting that Sundar et al.
Al2O3 focused on the behavior of
nanofluids by suspending Al2O3 particles
in 60EGW, 40EGW and 20EGW base fluids – relative to their weights. To
establish the values of thermal conductivity, the temperature ranges
that characterized the experimental conditions were 20 to
60oC [39]. Also, the rate of concentration of the
experimental materials was set between 0.3 and 1.5%. In the results,
the authors reported 32.26% as the maximum rate of enhancement. These
results held when 1.5% was set as the volume concentration, as well as
20EGW as the base fluid. Also, the results emerged after the temperature
of the experimental conditions was set at 60°C [40].
In circumpolar countries and other cold regions such as Alaska and
Canada, most of the industrial plants’ heat exchangers and automobiles
have seen heat transfer fluids used widely. With subzero temperatures
experienced, the fluids have also been used in building heating systems
[37]. The eventuality is that propylene glycol or ethylene glycol
have gained increasing use, having been mixed with water in varying
proportions to serve the purpose of heat transfer [41]. However,
propylene glycol solutions are seen to perform inferiorly compared to
ethylene glycol solutions, with the factor of heat transfer property on
focus. This outcome is also more pronounced in situations involving low
temperatures. In situations involving cold climates, it is imperatively
notable that 40% water and 60% ethylene glycol (translating into 40EGW
is used [21,42]. However, the case of countries experiencing hot
temperatures has seen this ratio altered to 60EGW (or 40:60). The
alteration is informed by the affirmations that with pure water, it is
challenging to maintain stability in these conditions [43]. In this
investigation, the base fluid saw the water and EG mixtures’ ratios used
as 40:60 and 60:40.
Other factors operating independent of the role of nano particles have
been investigated and documented relative to the nanofluids’ thermal
conductivity enhancement. Some of these factors include viscosity,
temperature, and thermal conductivity. As such, this study strived to
determine the thermal conductivity and viscosity properties of 40EGW and
60EGW base fluids. Given the base fluids, nano particles were dispersed,
which SiO2 utilized as the nanofluids. In the section
that follows, the manner in which the nanofluids were selected and
prepared is described. The third section focuses on the experimental
process that was employed towards investigating the viscosity and
thermal conductivity of the materials. The fourth section offers the
study’s resultant regression analysis, culminating into the fifth
section that focuses on the experimental outcomes relative to the
parameters of viscosity and thermal conductivity (in the form of a
comparative analysis). Lastly, the sixth section provides a conclusion,
which is a summary of the insights that were gained from this study.
Nanofluid Preparation
Methodology
Initially, water forms a component of heat transfer, pointing to its
wide-scale use as a liquid cooling applicant. Properties that account
for this wide usage include low velocity and high thermal conductivity,
as well as high heat capacity. The latter properties also imply that the
fluid can be pumped easily. However, it is imperative to acknowledge
that water exhibits a high freezing point, coming in the wake of the
fluid’s associated low boiling point. Furthermore, failure to maintain
the pH at a neutral level implies that water could prove corrosive.
These trends have seen scholarly attention directed to the use of
ethylene glycol. The growing use of the material is attributed to its
antifreeze properties. Hence, ethylene glycol has been used in
situations such as those involving chilled water air condition systems
whose handlers or chillers are kept outside. Also, the material has
gained growing use in systems requiring to be cooled at a freezing
temperature that is lower than that of water [44]. Figure 1 below
summarizes the flowchart of the methodology that this study employed.