We investigate the application of the method of moments approach for the one-dimensional population balance equation. We consider different types of moment closures, namely polynomial (P N ) closures, maximum entropy (M N ) closures and the quadrature method of moments QM OM N . Realizability issues and implementation details are discussed. The numerical examples range from spatially homogeneous cases to a population balance equation coupled with fluid dynamic equations for a lid-driven cavity test case. A detailed numerical discussion of accuracy, order of the moment method and computational time is given.Keywords: population balance, maximum entropy, quadrature method of moments 2010 MSC: 35L40, 45K05, 35R09
IntroductionPopulation balance equations are widely used in engineering applications, including aerosol physics, high shear granulation, pharmaceutical industries, polymerization and emulsion processes, evaporation and condensation processes in bubble column reactors, bioreactors, turbulent flame reactors and many others, see [13,19,24,24,[43][44][45] and references therein. These polydisperse processes are characterized by two phases: one of them is the continuous and the second is a dispersed phase consisting of particles. The particles can take different forms like crystals, drops or bubbles with several possible properties such as volume, chemical composition, porosity and enthalpy. In this work only the volume is considered. The dynamic evolution of the particle number distribution which is described by the population balance equation (PBE) of the dispersed phase depends not only on the particle-particle interactions, but also on the continuous phase, due to interaction of these particles with the continuous flow field in which they are dispersed. These interactions usually result in the common mechanisms aggregation, breakage, condensation, growth and nucleation. In our work we concentrate on binary aggregation, namely the Smoluchowski aggregation [42] and multiple breakages, since binary breakage is not sufficient for some of these applications. Binary aggregation is the process of merging two particles to a larger particle, whereas in a breakage process, a particle breaks into several smaller fragments. Often included in a typical PBE are spatial transport terms, i.e. advection and diffusion terms. We use the simplest case and assume that the mean particle velocity is the same as those of the fluid. The resulting population balance equations range from integro-differential to partial integro-differential equations of hyperbolic or parabolic type in phase space, in addition to the differential terms for advection and diffusion in the physical space.