## 3 Results and Discussion
### Thermal Properties of Electro-Insulating Liquids Modified by Fullerene C\({}_{60}\)
On the other hand, in the case of esters, the transfer in the thermal conductivity will have greater significance in this layer. This is mainly due to the higher thermal conductivity of the esters compared to mineral \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Kind of Liquid**} & \multicolumn{2}{c}{**Temperature**} & \multirow{2}{*}{**Gr**} & \multirow{2}{*}{**Pr**} & \multirow{2}{*}{**Nu**} \\ \cline{2-2} \cline{6-6}  & [\({}^{\circ}\)C] & & & \\ \hline \multirow{4}{*}{MO} & 25 & 7.9 \(\times\) 10\({}^{8}\) & 212 & 736 \\  & 40 & 21.9 \(\times\) 10\({}^{8}\) & 125 & 869 \\  & 60 & 61.6 \(\times\) 10\({}^{8}\) & 74 & 1028 \\  & 80 & 137.4 \(\times\) 10\({}^{8}\) & 50 & 1178 \\ \hline \multirow{4}{*}{MO + C\({}_{60}\)} & 25 & 7.6 \(\times\) 10\({}^{8}\) & 221 & 737 \\  & 40 & 20.7 \(\times\) 10\({}^{8}\) & 131 & 866 \\  & 60 & 59.3 \(\times\) 10\({}^{8}\) & 77 & 1030 \\  & 80 & 125.1 \(\times\) 10\({}^{8}\) & 53 & 1164 \\ \hline \multirow{4}{*}{SE} & 25 & 0.9 \(\times\) 10\({}^{8}\) & 641 & 520 \\  & 40 & 3.0 \(\times\) 10\({}^{8}\) & 339 & 623 \\  & 60 & 10.3 \(\times\) 10\({}^{8}\) & 177 & 757 \\  & 80 & 26.9 \(\times\) 10\({}^{8}\) & 107 & 884 \\ \hline \multirow{4}{*}{SE + C\({}_{60}\)} & 25 & 0.9 \(\times\) 10\({}^{8}\) & 660 & 521 \\  & 40 & 2.9 \(\times\) 10\({}^{8}\) & 348 & 623 \\  & 60 & 9.7 \(\times\) 10\({}^{8}\) & 185 & 756 \\  & 80 & 25.8 \(\times\) 10\({}^{8}\) & 111 & 882 \\ \hline \multirow{4}{*}{NE} & 25 & 0.8 \(\times\) 10\({}^{8}\) & 575 & 480 \\  & 40 & 2.1 \(\times\) 10\({}^{8}\) & 343 & 559 \\  & 60 & 6.0 \(\times\) 10\({}^{8}\) & 199 & 657 \\  & 80 & 13.7 \(\times\) 10\({}^{8}\) & 131 & 755 \\ \hline \multirow{4}{*}{NE + C\({}_{60}\)} & 25 & 0.8 \(\times\) 10\({}^{8}\) & 580 & 480 \\  & 40 & 2.1 \(\times\) 10\({}^{8}\) & 347 & 562 \\ \cline{1-1}  & 60 & 5.9 \(\times\) 10\({}^{8}\) & 203 & 661 \\ \cline{1-1}  & 80 & 13.6 \(\times\) 10\({}^{8}\) & 134 & 758 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Calculation results of the Grashof, Prandtl, and Nusselt numbers of pure electro-insulating liquids and nanofluids based on fullerene C\({}_{60}\). oil. Modification of electro-insulating liquids with fullerene C\({}_{60}\) does not significantly change the Nusselt number. Table 5 presents the results of calculations of temperature decrease in pure electro-insulating liquids and nanofluids based on fullerene C\({}_{60}\). The temperature decrease was determined based on Equation (9). Analyzing the calculated temperature decreases, it can be concluded that the modification of electro-insulating liquids with fullerene C\({}_{60}\) does not significantly affect the heat transport in the obtained nanofluids. Bearing in mind that fullerene C\({}_{60}\) is mainly used to improve dielectric properties [65; 66] and to absorb free radicals and to slow the acidification of vegetable oils [50; 51], it can be concluded that it does not impair the cooling efficiency of the device. Thermal Properties of Electro-Insulating Liquids Modified by Surfactant Span(r) 20 and Titanium Dioxide (TiO\({}_{2}\))  
Table 6 presents measured values of the thermal properties of analyzed electro-insulating liquids and nanofluids based on surfactant Span(r) 20 and titanium dioxide TiO\({}_{2}\) nanoparticles. In order to eliminate the influence of surfactant on the thermal properties of the resulting nanofluids, the results of the measurements of thermal properties of base liquids modified with surfactant are also presented. Similarly to the previous case, it was noticed that the modification of electro-insulating liquids with a surfactant did not cause changes in thermal conductivity, density, or thermal expansion. The increase in kinematic viscosity was clearly observable, which was due to the higher viscosity of the surfactant compared to the viscosity of the analyzed electro-insulating liquids.