Horizontal injection spray drying aerosol generator using an ultrasonic nozzle with clean counter flow

We investigated a spray-drying aerosol generator that can generate micro-particles at high concentration using an ultrasonic nozzle. Unlike a conventional spray-drying aerosol generator that uses vertical spray with co-current sheath flow, we designed a new aerosol generator by using horizontal spray with co-current sheath flow combined with clean counter flow to increase particle generation efficiency. A drying chamber was designed using the ANSYS Fluent solver to complete the evaporation of droplets and to minimize the loss of post-evaporation particles inside the chamber. Both numerical prediction and experimental data showed that droplets would completely evaporate at a temperature of 353 K. Both KCl aqueous solution and silica powder suspension were sprayed using an ultrasonic nozzle to generate micro-sized particles with a size range of 1–10 μm. When horizontal spray with co-current sheath flow was operated with clean counter flow the loss of particles on the chamber wall was minimized and thus the total particle number concentration was 2.4 times higher than when the clean counter flow was inactive. The particle generator in the present study can generate larger particles than a Collison atomizer which generates particles up to 3 μm.