A CFD-based compartmental model development for an LDPE production process

Purpose We developed a novel hybrid compartmental/computational fluid dynamics (CFD) approach that combines the accuracy of CFD for hydrodynamics with the computational efficiency of compartmental models for reaction modeling. This approach introduces significant innovations: an automatic zoning algorithm based on logarithmic velocity distribution and a direct method for inter-zonal flow rate determination without approximation. The methodology was validated on an industrial low-density polyethylene (LDPE) autoclave reactor, demonstrating a dramatic reduction in computational cost compared to full CFD simulations while maintaining acceptable engineering accuracy. Hydrodynamic validation was performed by comparing the residence time distribution (RTD) predicted by our model with CFD-derived RTD, while reaction validation compared our polymerization results with published CFD studies. The validated model was then used to efficiently investigate the effects of operating parameters on reactor performance, including feed inlet velocity and temperature, demonstrating the practical utility of this approach for parametric studies and process optimization of complex industrial reactors. Design/methodology/approach A hybrid compartmental/CFD method, as a link between the compartmental model and CFD, based on an automatic zoning and flow rate determination algorithm. Findings The method was applied to a LDPE reactor as a case study. In order to validate the predicted hydrodynamics by the model, the RTD diagram of the reactor was compared with the RTD of hybrid compartmental/CFD approach. RTD validation revealed the existence of a bypass stream in the reactor, and reaction validation showed that this method can model low progressive reactions in chemical processes properly. Finally, the effect of feed inlet velocity and its inlet temperature on the reactor performance was investigated as a sensitivity analysis. Originality/value This work introduces three key innovations in hybrid compartmental/CFD modeling: (1) an automatic zoning algorithm using logarithmic velocity distribution for uniform zone identification across varying flow regimes, (2) a direct method for calculating inter-zonal flow rates without approximation, and (3) integrated validation of both hydrodynamics (RTD) and reactions in a single framework. Applied to a 500L industrial LDPE autoclave reactor, the methodology achieves dramatic computational cost reduction compared to full CFD while maintaining engineering accuracy. This provides a practical tool for industrial applications requiring multiple simulations—design optimization, parametric studies, and process control development—where full CFD is prohibitively expensive. The framework is generalizable to reactor systems where reactions minimally affect hydrodynamics, offering a balance between computational efficiency and accuracy for industrial-scale process modeling. Highlights