An experimental study on stability and some thermophysical properties of multiwalled carbon nanotubes with water-ethylene glycol mixtures

In this study, the stability and thermophysical properties of multiwalled carbon nanotubes (MWCNTs) with double-distilled water (W) and double-distilled water/ethylene glycol (W/EG) mixtures are investigated. Stability analyses are performed through visual observation, thermal conductivity measurements, spectrophotometry and zeta potential measurement methods. An increase in ethylene glycol ratio in water increases the stability of nanofluid, which helps the nanoparticles disperse uniformly in the base fluid for a longer duration. It is concluded from the results that MWCNT nanofluids with a W/EG system (50: 50) has good stability, showing no agglomeration for 36 d as compared with other nanofluids. Thermophysical properties such as thermal conductivity, viscosity and density with temperature were also measured. Maximum thermal conductivity enhancement of 29% was observed for MWCNT-nanofluid with W/EG system (50: 50) at 50 degrees C. It is also observed that with the addition of MWCNT in W/EG mixtures, viscosity and density increase but the enhancement was comparatively low with reference to thermal conductivity. From these results, it was interpreted that both stability and thermal conductivity increase with increase in ethylene glycol ratio in water.