Particle coagulation, diffusion and thermophoresis in laminar tube flows

Abstract This is a theoretical study of simultaneous diffusion, thermophoresis and coagulation of submicron aerosols in non-isothermal laminar tube flows. Approximating the aerosol size distribution by a lognormal function, the general dynamic equation for aerosols is transformed to three ordinary differential equations which are solved, along with the heat equation, across the tube. The performance of this model is validated by comparing its predictions with literature results for pure particle diffusion, pure particle coagulation and pure thermophoresis. The interplay between these aerosol processes is investigated in the parameter space of the model focusing on the overall particle deposition efficiency (or, inversely, penetration). Aerosol penetration curves for non-isothermal, laminar tube flows are presented in the presence and absence of coagulation. Applications of this work are in the non-isothermal transport of particle laden streams through circular tubes (heat exchangers) and in the manufacture of lightguide preforms by modified chemical vapor deposition.

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