Measurements of pH of Three Nanofluids and Development of New Correlations

Abstract

In this study the pH levels of aluminum oxide (Al2O3), silicon dioxide (SiO2), and zinc oxide (ZnO) nanoparticles dispersed in propylene glycol and water mixture were measured in the temperature range of 0°C to 90°C. The volumetric concentration of nanoparticles in these fluids ranged from 0 to 10% for different nanofluids. The average particle sizes (APS) considered were from 10 nm to 70 nm. The pH measuring apparatus and the measurement procedure were validated by measuring the pH of a calibration fluid, whose properties are known accurately. The measured pH values agreed within less than ±0.5% with the published data reported by the manufacturer. Following the validation, the pH values of different nanofluids were measured. The measurements showed that pH of nanofluids decreased with an increase in temperature and increased with an increase in particle volumetric concentration. For the same nanofluid at a fixed volumetric concentration, the pH was found to be higher for larger particle sizes. From the experimental data, empirical models were developed for three nanofluids to express the pH as functions of temperature, volumetric concentration, and the size of the nanoparticles.