The changes induced by pH in TiO2/water nanofluids: Stability, thermophysical properties and thermal performance

The effects of pH on stability and thermophysical properties of TiO2/water nanofluids are seldom investigated, as well as the performance in heat applications. In this study, the effects of pH (ranging 2-12) on stability are firstly investigated. Then the thermophysical properties are examined with temperature from 25 degrees C to 60 degrees C. Finally, the performance in heat applications is evaluated. The results show that, the further away from the determined isoelectric point (pH = 6.5), the more stable is the nanofluid. Dynamic viscosity is highly related to stability, for better stability would result in lower viscosity. Thermal conductivity is dependent on the degree of aggregation, and higher thermal conductivity is found in the nanofluids with pH 2 and 10. Thermal conductivity would increase with the temperature, while an opposite trend is found in dynamic viscosity. Finally, the heat transfer performance of pH treated TiO2/water nanofluids is evaluated. (C) 2020 Elsevier B.V. All rights reserved.