Mass flow meter
The mass flow meter does not measure the volume per unit time (e.g., cubic meters per second) passing through the device; it measures the mass per unit time (e.g., kilograms per second) flowing through the device. Volumetric flow rate is the mass flow rate divided by the fluid density. If the density is constant, then the relationship is simple. If the fluid has varying density, then the relationship is not simple. The density of the fluid may change with temperature, pressure, or composition, for example. The fluid may also be a combination of phases such as a fluid with entrained bubbles.
Actual density can be determined due to dependency of sound velocity on the controlled liquid concentration.
Köhler theory
where formula_2 is the droplet water vapor pressure, formula_3 is the corresponding saturation vapor pressure over a flat surface, formula_4 is the droplet surface tension, formula_5 is the density of pure water, formula_6 is the moles of solute, formula_7 is the molecular weight of water, and formula_8 is the cloud drop diameter.