Simple equations to describe aerosol growth

A simple set of one algebraic equation and two ordinary differential equations is proposed to describe an aerosol growth process simultaneously involving nucleation, condensation/evaporation and coagulation using a monodisperse approach. With the assumption of spherical particles in a gas-volume-based environment, this method is applicable to both the free molecular size and the continuum size regimes, although it is not of use in the transition regime because it does not take into account the dynamics of transition. Despite its much simpler mathematical formulation and lower computational costs, this method gives reasonable numerical results for the particle number concentration and the particle size. These results practically coincide with those obtained with a more complex and elaborate method using the moments of a size distribution function. Modification of the equations to express different probabilities for particle fusion on impact is also suggested.