Abstract 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 °C to 60 °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.

中文翻译：

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TiO2/水纳米流体中pH值引起的变化：稳定性、热物理性质和热性能

摘要 很少研究 pH 值对 TiO2/水纳米流体的稳定性和热物理性质以及热应用性能的影响。在这项研究中，首先研究了 pH 值（范围 2-12）对稳定性的影响。然后在 25 °C 至 60 °C 的温度下检查热物理性能。最后，评估在热应用中的性能。结果表明，离确定的等电点（pH = 6.5）越远，纳米流体越稳定。动态粘度与稳定性高度相关，稳定性越高，粘度越低。热导率取决于聚集程度，在 pH 2 和 10 的纳米流体中发现更高的热导率。热导率会随着温度的升高而增加，而动态粘度则呈现相反的趋势。最后，评估了 pH 处理的 TiO2/水纳米流体的传热性能。