Influence of pH on the Stability Characteristics of Nanofluids for Heat Transfer Applications

Nanofluids have been in intense researches for the past few years with the great potential to improve the efficiency of heat transfer fluids. Knowledge of sediment behaviours of nanofluids give great significances towards the stability of nano-suspensions. This work focuses on the sedimentation behaviours of alumina and zinc oxide nanoparticles in different proportion of ethanol-water binary mixtures. Nanoparticles of 40 nm were used in this project. Under different pH values, the sediment heights with respect to time were measured by visualization method in batch sedimentation. Analysis of TEM, FTIR, zeta potential and particle size distribution were performed to study the influence of pH on the nanofluids. The results showed that in certain ethanol-water proportions, the stability of alumina nanofluids was highly dependent on pH values. The highest stability of the alumina nanofluids can be achieved at the optimal pH value. Whereas pH was found to have insignificant effects on the stability of zinc oxide nanofluids.