An Experimental Investigation into Stability and Thermal Conductivity of Nanofluids

Abstract

This thesis presents an experimental investigation into the stability and thermal conductivity of nanofluids. In the present work the stability of 3 different nanoparticles – Silver, Carbon nanotubes, Zinc Oxide have been investigated. These three have been chosen as the representatives of the different classes of nanoparticles – metal, carbon nanotubes and metal oxide respectively. Three popular techniques have been used to investigate into the stability of nanofluids – Dynamic Light Scattering, UV-vis spectrophotometer and Zeta Potential and their results have been compared. Also, the effect of sonication time and addition of SDS (sodium dodecylsulfate) as surfactant have been investigated to see how they affect the stability of a nanofluid. The issue of measurement of thermal conductivity has been dealt with including a review of the different methods that have been used to measure the thermal conductivity and the establishment of the correct technique to use the KD2 Pro to see how stability of a nanofluid affects its thermal conductivity. The Carbon nanotubes have been found to be the most stable of all the nanofluids that have been used. Zinc Oxide is the least stable of all. The spectrophotometer technique gives the best estimate of the stability of a nanofluid. Also, thermal conductivity has been found to be a function of size and concentration of the nanoparticles, and it increases as the particles agglomerate to form clusters; however it decreases as the particles become too large as they begin to settle down and that decreases the concentration of the nanoparticles in the base fluid.