Mechanistic Investigations of Viscosity and Thermal Conductivity Enhancement in Multi-Walled Carbon Nanotubes-Propylene Glycol Nanofluids

Experiments were performed on the formulation of MWCNT-Propylene glycol nanofluid through acid-treatment of MWCNT followed by ultrasonication. While acid-treatment introduced hydrophilic groups to facilitate dispersion in a polar liquid like propylene glycol, probe ultrasonication contributed to de-agglomeration of large clusters. The viscosity of acid-treated MWCNT-propylene glycol increases non-linearly with MWCNT volume concentration due to high aspect ratio and clustering. The analysis of viscosity and thermal conductivity data as a function of MWCNT concentration and temperature reveal the role of particle clustering in thermal conductivity enhancement. The nanofluid maintains colloidal stability even at temperatures as high as 140 degrees C.