This article presents a numerical simulation procedure for studying soot particle deposition in diesel exhaust systems, with a particular focus on fouling layer thickness evolution. In the proposed algorithm, particle transport toward the wall, adhesion, and reentrainment of particles from the surface have been modeled, including Brownian motion and turbulent diffusion, thermophoresis, adhesion, and removal. This model has been implemented in ANSYS Fluent, which makes the inclusion of local effects possible. A cross-flow device, with a tube positioned transverse to the flow, has been simulated and tested. A comparison of the predicted fouling layer at several angular positions with the experimental observation shows acceptable agreement. This model makes it possible to predict the real depth of the fouling layer and its effects on the hydrodynamics of the flow. This model represents a valuable tool for the prediction of the main aspects of the performance of heat exchangers exposed to fouling.