Determination of droplet sizes in a gas-droplet outflow from a microchannel nozzle device

To generate a spray flow in confined spaces, it is necessary to develop specialized nozzles capable of dispersing micron- and submicron-sized droplets at the nozzle edge. A high-speed visualization of a gas-droplet flow from a specially manufactured microchannel nozzle device with a resolution of 2.5 µm/pixel was performed, allowing for the determination of sizes of the dispersed droplets. The nozzle was a specially fabricated device composed of a 243 µm-thick microchannel silicon membrane and a microchannel size of 10 × 10 µm 2 . The characteristic sizes and velocities of the dispersed droplets were measured at low liquid flow rates (0.05–2 ml/min) and air pressure drops from 1 to 6 atm. At a HFE-7100 flow rate of 1 ml/min and an air pressure drop of 1 atm, the average droplet size was approximately 40 µm, while at a flow rate of 2 ml/min and a pressure drop of 2 atm, it was 20 µm. A substantial increase in velocity was observed with increasing pressure drop. At the minimum flow rate, the dispersion of very small droplets was observed, which were not detected at a resolution of 2.5 µm/pixel. However, the overall flow was clearly visible as a “mist”.