CFD-BASED ANALYSIS OF THE FLOW REGIME IN THE CENTRIFUGAL MOLECULAR DISTILLATION OF A PETROLEUM ATMOSPHERIC RESIDUE

摘要

The characterization of the flow in the evaporating liquid film, well distributed on the inner wall of the evaporator surface, is of paramount importance to the fluid dynamics within the molecular distillation process performance. This work aims to investigate the effect of the different operating conditions (feed flow rate and rotor speed) at constant evaporator temperature (423.15 K) on the velocity profile in the thin liquid film of an atmospheric residue of petroleum on the evaporator surface of a centrifugal molecular distiller. The analyses were carried out using computational fluid dynamics (CFD) simulations, making use of the commercial software ANSYS CFX 11.0 (of Ansys Inc., EUROPE) based on a finite volume method. A laminar flow model and two turbulence flow models (the standard k-ε and the SST k-ω’ turbulence models) were considered. A comprehensive model based on the Navier–Stokes and continuity equations represented the computational model. The simulations show an overall good agreement with the point up of molecular distillation process, based on the fact that the feed flow rate at the inlet of the device has an important effect on the velocity distribution. Results suggest that the standard k-ε and the SST k-ω’ turbulence models are suitable for simulating evaporating liquid film in centrifugal molecular distiller. Nevertheless, small differences between the results obtained with turbulence and laminar models were found. Hence, laminar flow model is sufficient for modeling centrifugal molecular distillations. The usefulness of the above information obtained from the CFD simulation and analysis will be elucidated for a modeling of a centrifugal molecular distillation process.