Optimization of dispersion conditions of Al₂O₃ nanoparticles in simulated cooling water

Nanofluids were prepared using Al₂O₃ nanoparticles in simulated cooling water. The stability of nanofluids was characterized by zeta potential. The effect of dodecyl benzene sulfonate (SDBS) concentration, sonication time, solution pH on the stability of nanofluids and the optimum conditions were researched in this paper. Results of single factor experiments revealed that the absolute value of zeta potential |ζ| of nanoparticles increased first but then decreased with the increase of the SDBS concentration, sonication time and pH value. Based on the preliminary experimental results, the box-behnken design (BBD) model of response surface methodology was applied to optimize nanoparticle dispersion conditions in simulated cooling water. Results showed that the contribution of SDBS concentration to |ζ| was maximum, than the solution pH value; the interactions between SDBS concentration and pH, sonication time and pH were relatively obvious; the optimal condition to obtain stable Al₂O₃ nanofluid achieved from BBD model was SDBS at weight concentration of 0.339%, ultrasonic time 61 min, pH value 8.05, and the predicted value of |ζ| was 50.8 mV. The experimental value of |ζ| at the optimal condition was 50.6 mV, which was very close to the predicted value.