Modelling of Nanoparticle Coagulation and Transport in Pipe Flow

Industrial interest in nanoparticles leads to concerns about their significant presence in workplaces. Their increased use may have particular consequences in terms of occupational hygiene when considering a potentially hazardous nano-structured aerosol. Between the source of nanoparticles and their deposition or inhalation, it is well known that coagulation phenomenon contributes to a quick change of the particle size distribution. In this context, a model of coagulation is therefore a useful tool for the evaluation and characterization of occupational exposures. A model without flow, based on the population balance approach taking into account the fractal dimension of aggregates, has already been validated on experimental results in a homogeneous closed chamber. We suggest here to include this population balance in the transport equations of computational fluid dynamics to obtain the spatiotemporal evolution of an aerosol of nanoparticles. The idea is to add a source term describing coagulation in the convection-diffusion equations for the moments of the particle-size distribution. In this paper we propose to evaluate this method by considering the transport and coagulation of the aerosol in a pipe presenting a uniform flow. This one-dimension flow is useful to validate the model implementation since corresponding analytical solutions exist. Next steps will consist in extending simulations to more realistic three-dimensional cases.