Abstract

In recent years the spray drying of nanofluids has become of great interest. This process allows obtaining nanostructured grains which preserve the chemical, mechanical, optical and electrical properties of nanoparti-cles. In this work, single droplets of SiO2-water nanofluids have been dried in an acoustic levitator modified to work at high temperatures under different experimental conditions. The influence of different variables on the drying behaviour and the grain properties has been studied. A commercial fumed silica powder with a diameter of 12 nm (Aerosil-200) has been used to prepare all the suspension tested. The evolution of the droplet position and diameter during the drying process has been recorded with a CMOS camera. With this information the dry-ing curves and the mean final grain porosity have been calculated. The effect of the solid mass load (0.02 w/w < Y_S < 0.20 w/w), suspension pH (2 < pH < 10), salt concentration (0 M < [NaCl] < 0.05 M), ambient air tempera-ture (80ºC < T < 120ºC) and initial droplet volume (0.3 μl < V0 < 0.8 μl) on the first period mass transfer rate and the final grain porosity has been studied.