In FLUENT the population balance model is provided as an addon module with the standard FLUENT licensed software. A special license is required to use the population balance module.
Several industrial fluid flow applications involve a secondary phase with a size distribution. The size distribution of particles, including solid particles, bubbles, or droplets, can evolve in conjunction with transport and chemical reaction in a multiphase system. The evolutionary processes can be a combination of different phenomena like nucleation, growth, dispersion, dissolution, aggregation, and breakage producing the dispersion. Thus in multiphase flows involving a size distribution, a balance equation is required to describe the changes in the particle population, in addition to momentum, mass, and energy balances. This balance is generally referred to as the population balance. Cases in which a population balance could apply include crystallization, precipitative reactions from a gas or liquid phase, bubble columns, gas sparging, sprays, fluidized bed polymerization, granulation, liquid-liquid emulsion and separation, and aerosol flows.
To make use of this modeling concept, a number density function is introduced to account for the particle population. With the aid of particle properties (e.g., particle size, porosity, composition, etc.), different particles in the population can be distinguished and their behavior can be described.
FLUENT offers three solution methods to the population balance equation: discretized population balance, standard method of moments, and quadrature method of moments.