Aiming at the dispersion stability of nanopartieles regarded as the guide of heat transfer enhancement, we investigate the viscosity and the thermal conductivity of Cu and Al2O3 nanoparticles in water under different ...Aiming at the dispersion stability of nanopartieles regarded as the guide of heat transfer enhancement, we investigate the viscosity and the thermal conductivity of Cu and Al2O3 nanoparticles in water under different pH values. The results show that there exists an optimal pH value for the lowest viscosity and the highest thermal conductivity, and that at the optimal pH value the nanofluids containing a small amount of nanoparticles have noticeably higher thermal conductivity than that of the base fluid without nanoparticles. For the two nanofluids the enhancements of thermal conductivity are observed up to 13% （Al2O3-water） or 15% （Cu-water） at 0.4 wt%, respectively. Therefore, adjusting the pH values is suggested to improve the stability and the thermal conductivity for practical applications of nanofluid.展开更多
Aiming at the dispersion stability of nanofluids,we investigate the absorbency and the zeta potential of TiO_(2) and Al2O3 nanofluids under different pH values and different dispersant concentrations.The results show ...Aiming at the dispersion stability of nanofluids,we investigate the absorbency and the zeta potential of TiO_(2) and Al2O3 nanofluids under different pH values and different dispersant concentrations.The results show that in the mass fraction 0.05%alumina and 0.01%titanium dioxide nanosuspensions,the absolute value of the zeta potential and the absorbency of the two nanofluids with sodium dodecyl sulfate(SDS)dispersant are the highest at an optimal pH(pHAl_(2)O_(3)≈6.0,pHTiO2≈9.5)and that there is a good correlation between absorbency and zeta potential:the higher the absolute value of the zeta potential is,the greater the absorbency is,and the better the stability of the system is.The optimizing concentrations for SDS are 0.10%and 0.14%,respectively,at which the two nanofluids have the best dispersion results.The calculated DLVO interparticle interaction potentials verify the experimental results of the pH effect on the stability behavior.展开更多
文摘Aiming at the dispersion stability of nanopartieles regarded as the guide of heat transfer enhancement, we investigate the viscosity and the thermal conductivity of Cu and Al2O3 nanoparticles in water under different pH values. The results show that there exists an optimal pH value for the lowest viscosity and the highest thermal conductivity, and that at the optimal pH value the nanofluids containing a small amount of nanoparticles have noticeably higher thermal conductivity than that of the base fluid without nanoparticles. For the two nanofluids the enhancements of thermal conductivity are observed up to 13% （Al2O3-water） or 15% （Cu-water） at 0.4 wt%, respectively. Therefore, adjusting the pH values is suggested to improve the stability and the thermal conductivity for practical applications of nanofluid.
基金by the National Natural Science Foundation of China under Grant No 11047021the Fund for Talent Introduction to Advanced Universities of Guangdong under Grant No 2009109and the Guangdong Natural Science Foundation under Grant No 10151064201000006.
文摘Aiming at the dispersion stability of nanofluids,we investigate the absorbency and the zeta potential of TiO_(2) and Al2O3 nanofluids under different pH values and different dispersant concentrations.The results show that in the mass fraction 0.05%alumina and 0.01%titanium dioxide nanosuspensions,the absolute value of the zeta potential and the absorbency of the two nanofluids with sodium dodecyl sulfate(SDS)dispersant are the highest at an optimal pH(pHAl_(2)O_(3)≈6.0,pHTiO2≈9.5)and that there is a good correlation between absorbency and zeta potential:the higher the absolute value of the zeta potential is,the greater the absorbency is,and the better the stability of the system is.The optimizing concentrations for SDS are 0.10%and 0.14%,respectively,at which the two nanofluids have the best dispersion results.The calculated DLVO interparticle interaction potentials verify the experimental results of the pH effect on the stability behavior.
