Synthesis and Characterization of Nanofluids …
15
Fig. 6 Effect of temperature on thermal conductivity of graphene–water nanofluids (Ahammed
et al. 2016)
It was also found that the solvent molecules get adhered and form layers of ordered
arrangement of molecules to the hydrophilic colloidal particles, that is, nanoparticles added to it (Lee 2008). This layer possesses higher thermal conductivity and
aids in increasing the heat transfer induced due to the nanoparticles (Keblinski et al.
2002). It is also well established by Suganthi et al. (2013) for ZnO-propylene glycol
nanofluids that the thickness of this layer is high at lower temperatures where Brownian motion fails to be occurring due to higher viscosities of the basefluid. Thus,
it was found that at a temperature of 10 °C, the liquid layer enhances the thermal
conductivity of the nanofluid and attains a maximum, which further decreases as
the temperature increases to 30 °C. This unusual but true mechanism of decrease in
thermal conductivity with increase in temperature is also found out for ZnO-ethylene
glycol nanofluids (Suganthi et al. 2014), as shown in Fig. 7.
3.3.5 pH
Nanofluid is a suspension of nano-sized material in some basefluid. Its uniform
dispersion in a typical basefluid shall definitely depend upon the charges on its
surface. The surface charges will affect the degree of agglomeration, which ultimately
15
Fig. 6 Effect of temperature on thermal conductivity of graphene–water nanofluids (Ahammed
et al. 2016)
It was also found that the solvent molecules get adhered and form layers of ordered
arrangement of molecules to the hydrophilic colloidal particles, that is, nanoparticles added to it (Lee 2008). This layer possesses higher thermal conductivity and
aids in increasing the heat transfer induced due to the nanoparticles (Keblinski et al.
2002). It is also well established by Suganthi et al. (2013) for ZnO-propylene glycol
nanofluids that the thickness of this layer is high at lower temperatures where Brownian motion fails to be occurring due to higher viscosities of the basefluid. Thus,
it was found that at a temperature of 10 °C, the liquid layer enhances the thermal
conductivity of the nanofluid and attains a maximum, which further decreases as
the temperature increases to 30 °C. This unusual but true mechanism of decrease in
thermal conductivity with increase in temperature is also found out for ZnO-ethylene
glycol nanofluids (Suganthi et al. 2014), as shown in Fig. 7.
3.3.5 pH
Nanofluid is a suspension of nano-sized material in some basefluid. Its uniform
dispersion in a typical basefluid shall definitely depend upon the charges on its
surface. The surface charges will affect the degree of agglomeration, which ultimately