Druppeldiameter

Druppeldiameter is a measure of the size of liquid droplets and is commonly defined as the diameter of a sphere with the same volume as the droplet. In practice, many droplet size descriptors are used, because real droplets are not perfect spheres. The most common definitions are the volume-equivalent diameter (also called the effective diameter), the area-equivalent diameter, and the Sauter mean diameter (d32), which relates droplet surface area to volume. The choice of definition depends on the application, such as evaporation, heat transfer, or light-scattering measurements.

Measuring droplet diameter is performed with several techniques. Optical methods include microscopy and shadowgraphy for collected samples, while in-flow methods include laser diffraction, phase Doppler interferometry, and digital inline holography. Each method yields different size descriptors (number, volume, or surface-area weighted distributions) and each has limitations in polydisperse or very small droplets.

Applications and relevance: Droplet size controls atomization quality, spray deposition, evaporation rate, and heat transfer performance. In agriculture, droplet diameter influences coverage and drift; in combustion, it affects burning efficiency; in inkjet printing, it determines resolution and drying.

Factors influencing droplet diameter include nozzle design, operating pressure, liquid properties such as viscosity and surface tension, and ambient conditions like temperature and air flow. The distribution is often broad, requiring a full size distribution or a single representative metric such as the Sauter diameter for comparisons.