## 5 Noble Nanofluids
### Silver Nanofluids  
There are many published theoretical and experimental research works on the impact of silver nanoparticles in the thermophysical characteristics enhancement of the nanofluids. In this direction, the authors [PERSON] et al. [44] produced an ethylene glycol-silver nanofluid through chemical reduction and found thermal conductivity enhancements of 10%, 16%, \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Authors** & **Morphology of the Nanoparticles** & **Concentration of the Nanoparticles** & **Base Fluid** & **Main Findings** & **Observations** & **Reference** \\ \hline [PERSON] et al. & Spheres, Triangles, and Rods & Ketone, alcohol, & Ketone, & Ketone and alcohol & & The gold triangles and & \\  & Spheres, Triangles, and Rods & Ketone, & alcohol, & nano-scaled spheres & & rods had more tendency & [39] \\  & and Rods & ACN, THF & ACN and THF formed & & to aggregate & \\  & & & & rods and triangles & & \\ \hline Nimmagadda & Spherical with & & & The nanofluid at 2 vol.\% & & Transfer efficiency & \\  & & & with 50 nm caused an & & increased with increasing & \\  & et al. & 50 nm and 70 nm & 2\% vol. & Water & & Increes in the & Reynolds number and it & \\  & et al. & & & convective heat transfer & was optimal in the & \\  & et al. & & & efficiency around 13\% & magnetic field located & \\  & & & & & along the X-axis & \\ \hline Zaaroura & Spherical with & & & The uncapped & & \\  & et al. & 10 nm & & nanofluids with PBS & & \\  & et al. & & & solution showed that & & \\  & & & & the nanoparticle size of & & \\  & & & & 5 nm caused the & & \\  & & & & greatest increase in the & & \\  & & & & evaporation rate of 35\% & & \\  & & & & & with 10 nm & Addition of \\  & et al. & & 10 nm & & & citrate-capping PBS and & [41] \\  & & & & & onpostic results, the & \\  & & & & larger nanoparticles of & & \\  & & & & 10 nm had the greatest & & \\  & & & & increase in the & & \\  & & & & evaporation rate of 15\% & \\  & & & & but still less than the & & \\  & & & & solution with PBS only & & \\ \hline [PERSON] et al. & Sphere and rod & & & The solar absorption & & \\  & with 20 nm & & & efficiently of the dimer & & \\  & & & & nanofluid was & & Utilization of a thin layer & \\  & & & & enhanced by 21.2\% & & of a plasmonic dimer & \\  & & with 200 ppm & & when compared with & & nanofluid composed of a & \\  & & & & the blended nanofluid & & sphere and rod in water & \\  & & & & & of sphere and rod & \\ \hline [PERSON] et al. & Spherical with & & & The less concentrated & & \\  & 14 \(\pm\) 2 nm & Two concentrations & & nanofluids were more & & Use of a shell and helically & \\  & & & & efficient, suggesting the presence of a range of & & coiled tube heat exchanger & \\  & & & around 10\({}^{-5}\)\% vol. & Water & & with flowrates of 20 l/h, & \\  & & & & & improving the & & \\  & & & & heat transfer & & \\ \hline [PERSON] et al. & Spherical with & & & The optimal Merit & & \\  & & & & Function of 195 and & & \\  & & & & energy efficiency of & \\  & & & & around 14\% was & & \\  & & & & Ethylene & achieved filtered by & \\  & & & Glycol & gold + PVP/ethylene & & \\  & & & & glycol nanofluid at & & \\  & & & & 29.2 ppm and & & \\  & & & & 2 mL/min. & & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: _Cont._and 18% in reference to the one of the ethylene glycol itself at concentrations of silver nanoparticles of 1000 ppm, 5000 ppm, and 10,000 ppm, respectively. Moreover, the authors [PERSON] et al. [45] achieved thermal conductivity enhancements of the ethylene glycol from nearly 6% to 21% at volumetric fractions of silver nanoparticles of 1% vol. and 2% vol. with varying nanoparticle sizes. The silver nanoparticles possess enhanced room temperature thermal conductivity of up to 429 W/mK and, consequently, are expected to fulfill the requirements of most of the heat transfer processes. Also, silver is usually taken as not hazardous for human health [46].