Study of aerosol behaviour in filmwise condensation processes with the presence of inert gas

The appearance of aerosols in condensation processes may result in a loss of condensate mass, a reduction of efficiency, pollution and damage to equipment. The presence of inert gases in condensation is frequent and can lead to the formation of aerosol particles. Equipment used in industrial condensation, gas cleaning, the removal of pollutants or the recovery of valuable substances comprise some examples of interest. The complexity of the physical phenomena occurring simultaneously makes the study of these systems difficult and it is thought that modelling might help to better understand their behaviour. A model has been developed in this study that includes the condensation of the gaseous mixture and phenomena related to the presence of liquid particles. The model solves the conservative equations for species continuity, energy and the number of liquid particles. It also includes the precipitation of liquid particles via thermophoresis, diffusiophoresis and gravitational deposition, homogeneous nucleation and coagulation induced by the Brownian movement of the particles. A condenser presenting a simple shell-and-tube geometry was selected and subjected to a unidimensional spatial discretization. The particle size interval of the aerosol population was discretized following a sectional method of moving intervals. The interaction between continuous and discrete phases was calculated as condensational growth in non-dilute and non-ideal media. Some cases were solved for water liquid particles and vapour mixed with air and a comparison was carried out using experimental data from a previous study from the literature providing a good fit. It was observed that the condensation rate is not radically altered by the presence of particles, although the persistence of remaining growing droplets dispersed in the gas could produce the aforementioned undesirable effects.