dropletsize

Dropletsize refers to the characteristic size of liquid droplets within a dispersed phase, such as sprays, aerosols, or emulsions. It is not a single value but a distribution, often described by metrics such as the volume median diameter (VMD) or the Sauter mean diameter (d32). Sizes are typically expressed in micrometers (µm).

In practice, dropletsize covers a broad range. Commonly produced droplets span from a few micrometers to several hundred micrometers, with the specific range determined by the atomization method, liquid properties, and operating conditions. For inhalation therapies, droplets designed for deep lung deposition are usually in the 1–5 µm range, while larger droplets deposit in the upper airways. In agricultural spraying and industrial coatings, droplets are often larger to improve coverage and reduce drift.

Measurement and characterization of dropletsize employ techniques such as laser diffraction, optical particle sizing, microscopy, and cascade impactors. Descriptions of a distribution often include a mean diameter (e.g., d32) and sometimes a span or polydispersity index to indicate the width of the distribution. The distribution is frequently approximately lognormal due to breakup and coalescence dynamics.

Factors that influence dropletsize include liquid properties (viscosity, surface tension, density), atomization mechanism (nozzle type, pressure, air assistance), and environmental conditions (temperature, humidity, airflow). Evaporation can reduce size during transit, especially for volatile or hygroscopic liquids, altering reach, residence time, and deposition patterns. Applications span spray technology, inhalation therapy, agriculture, coatings, and inkjet printing.