A computational fluid dynamics (CFD) model for particulate fouling in heat exchangers has been developed. Particulate fouling is generally considered as a serial process of the transport of the particles into the vicinity of the wall and the adherence on the surface. Particle adhesion on the surface is described by a mass transfer coefficient based on the XDLVO theory. For modelling particle transport, the generally accepted models were applied. A wall function approach was developed for calculating the near-wall particle transport in order to avoid the use of excessively small computational cells. The model is based on the assumption of local equilibrium of the forces affecting the particle transport. The wall function model is compared to a detailed CFD model and to experimental results from a fouling test apparatus using the assumption of a smooth and already fouled surface. Comparisons were made with several heat fluxes and mass flow rates applying various high concentrations of colloidal calcium carbonate (CaCO3) particles suspended in water. Results of simulations are in fairly good agreement with measurements. The wall function model allows the applications of coarser computational grids and therefore modelling of practical industrial heat exchangers.
- heat exhanger
- multiphase flow