| Article ID | Journal | Published Year | Pages | File Type |
|---|---|---|---|---|
| 651825 | Experimental Thermal and Fluid Science | 2012 | 8 Pages |
Addition of surfactants into the fluids is often used to minimize particle aggregation and improve dispersion behavior of nanofluids. However, they also affect the physical characteristics of liquids, such as, thermal conductivity and viscosity. In this paper, the thermal conductivity and viscosity of several common used surfactant solutions are investigated experimentally, with regard to the effect of critical factors such as concentration, temperature and pH value. The results show that the thermal conductivity ratios of surfactant solutions keep stable after a certain concentration. Compared with non-ionic surfactants, the ionic surfactants are more sensitive to temperature. With the increase of temperature, the thermal conductivities of three ionic surfactants gradually approach the value of pure water. Both strong alkaline and acidic mediums go against the improvement of thermal conductivity of surfactant solutions. The zero-shear viscosity of polyvinylpyrrolidone (PVP) solution at 4.0 wt% is about twice than that of water, while the viscosity of an ionic surfactant does not increase noticeably at low concentration. Therefore, an appropriate combined treatment addressing concentration, temperature and pH is recommended to improve the thermal conductivity and viscosity of the base fluid and thereby for practical applications of nanofluids.
Graphical abstractIn this research, the thermal conductivities of surfactant solutions are measured by the transient plane source (TPS) technique. The figure presents the thermal conductivity ratio of surfactant solutions and deionized water with respect to the concentration of surfactants at room temperature. Where, k and k0 represent the thermal conductivities of the surfactant solutions and water, respectively. As shown in the figure, all the surfactants reach a stable thermal conductivity ratio after a certain concentration. Comparing with the ratios in the stable section, they are mainly depending on the kind of surfactant and on the length of Alkyl chain. Generally, the ratios of ionic surfactants are higher than that of non-ionic surfactant. For the same kind of surfactant, the ratio of SDS, with a shorter Alkyl chain, is higher than that of SDBS.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► The thermal conductivity and viscosity of several common used surfactant solutions are investigated. ► Discussing the effect of factors such as concentration, temperature and pH value. ► The thermal conductivity ratios of surfactant solutions keep stable after a certain concentration. ► Both strong alkaline and strong acidic mediums go against the improvement of thermal conductivity of surfactant solutions.
