Multiphase Eulerian-Lagrangian LES of particulate fouling on structured heat transfer surfaces

摘要

In this study, multiphase Eulerian-Lagrangian large-eddy simulation (LES) is used to analyze the interaction between local flow structures, convective heat transfer and particle depositions (fouling) for a turbulent channel flow with a dimpled surface. Thus, eddy-resolving LES is applied for calculation of the turbulent working fluid (carrier flow), combined with an efficient Lagrangian particle tracking (LPT) algorithm, suitable to predict the trajectories of the suspended foulant particles precisely in time and space. In order to decrease the computational effort and to enhance the applicability of the proposed approach, deposited particles are deactivated and converted into a second continuous phase (fouling layer), which is modeled as a porous medium and accounts for the hydraulic losses as well as for the additional thermal resistance due to the fouling deposits. Prior to the fouling simulations, the envisaged method is validated for a turbulent particle-laden channel flow at Re-tau = 150, based on DNS results available in the literature, which shows the capability of the Eulerian-Lagriangian LES of capturing the flow physics within turbulent particle-laden, wall-bounded flows. Based on this observations, fouling simulations were carried out for a turbulent particle-laden channel flow over a staggered arrangement of sharp-edged spherical dimples, whereby two different dimple depth-to-diameter ratios are considered (d/D = 0.26 and 0.35). The thermo-hydraulic performance is analyzed for the clean and contaminated dimpled surfaces.