Particle size (general)

The term particle size is used to compare dimensions of different small material objects.

Larger objects are usually called stone, rock, a piece of something, etc. The term particle indicates small size, usually less than centimeter. Particle might be either solid, or liquid, or even gas. Liquid particles are called droplets. Gaseous particles are bubbles. All of them can be characterised in terms of size.

• Particle size of spherical object equals to its diameter.

But a typical material object is likely to be irregular in shape. This causes ambiguity in definition of particle size. Existing definitions are based on replacent of a given particle with imaginary sphere that has one of the properties identical with the particle.

• Volume based particle size equals to the diameter of the sphere that has same volume as a given particle;
• Weight based particle size equals to the diameter of the sphere that has same weight as a given particle;
• Area based particle size equals to the diameter of the sphere that has the same surface area as a given particle;
• Hydrodynamic particle size equals to the diameter of the sphere that has the same drag coefficient as a given particle;