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CFD-based Shape Optimization of Structured Packings for Enhancing Separation Efficiency in Distillation

Sebastian Blauth, Dennis Stucke, Mohamed Adel Ashour, Johannes Schnebele, Thomas Grützner, Christian Leithäuser

TL;DR

This work addresses enhancing separation efficiency in lab-scale distillation by applying free-form, CAD-free shape optimization to a structured packing (RP9M-3D) using a simplified CFD surrogate for mass transfer. The optimization maximizes the logarithmic mass transfer coefficient $\beta$ under PDE constraints derived from the Navier–Stokes and convection-diffusion equations, implemented with adjoint-based tools and validated against high-fidelity simulations. The optimized geometry yields about a 20% gain in separation performance, which is corroborated by experimental 3D-printed tests showing a similar improvement, albeit with higher pressure drop. The study demonstrates the feasibility of CAD-free optimization for packing design and highlights directions for future multi-criteria optimization and more realistic two-phase modeling to balance mass transfer against pressure losses in practical applications.

Abstract

Free-form shape optimization techniques are investigated to improve the separation efficiency of structured packings in laboratory-scale distillation columns. A simplified simulation model based on computational fluid dynamics (CFD) for the mass transfer in the distillation column is used and a corresponding shape optimization problem is formulated. The goal of the optimization is to increase the mass transfer in the column by changing the packing's shape, which has been previously used as criterion for increasing the separation efficiency of the column. The computational shape optimization yields promising results, with an increased mass transfer of nearly 20 %. For validation, the resulting optimized shape is additively manufactured using 3D-printing and investigated experimentally. The experimental results are in good agreement with the performance improvement predicted by the computational model, yielding an increase in separation efficiency of around 20 %.

CFD-based Shape Optimization of Structured Packings for Enhancing Separation Efficiency in Distillation

TL;DR

This work addresses enhancing separation efficiency in lab-scale distillation by applying free-form, CAD-free shape optimization to a structured packing (RP9M-3D) using a simplified CFD surrogate for mass transfer. The optimization maximizes the logarithmic mass transfer coefficient under PDE constraints derived from the Navier–Stokes and convection-diffusion equations, implemented with adjoint-based tools and validated against high-fidelity simulations. The optimized geometry yields about a 20% gain in separation performance, which is corroborated by experimental 3D-printed tests showing a similar improvement, albeit with higher pressure drop. The study demonstrates the feasibility of CAD-free optimization for packing design and highlights directions for future multi-criteria optimization and more realistic two-phase modeling to balance mass transfer against pressure losses in practical applications.

Abstract

Free-form shape optimization techniques are investigated to improve the separation efficiency of structured packings in laboratory-scale distillation columns. A simplified simulation model based on computational fluid dynamics (CFD) for the mass transfer in the distillation column is used and a corresponding shape optimization problem is formulated. The goal of the optimization is to increase the mass transfer in the column by changing the packing's shape, which has been previously used as criterion for increasing the separation efficiency of the column. The computational shape optimization yields promising results, with an increased mass transfer of nearly 20 %. For validation, the resulting optimized shape is additively manufactured using 3D-printing and investigated experimentally. The experimental results are in good agreement with the performance improvement predicted by the computational model, yielding an increase in separation efficiency of around 20 %.
Paper Structure (14 sections, 6 equations, 4 figures)

This paper contains 14 sections, 6 equations, 4 figures.

Table of Contents

  1. Introduction
  2. Materials and Methods
  3. Packing structure
  4. Experimental Methods
  5. Simulation Methods
  6. Simulation Model
  7. Shape Optimization
  8. Results and Discussion
  9. Shape Optimization of the Packing
  10. Experimental Validation of the Optimized Design
  11. Conclusions and Outlook
  12. Details for the Simulations
  13. Details for the Ansys® Fluent Simulation
  14. Details for the FEniCS Simulation

Figures (4)

  • Figure 1: Experimental and simulation setup.
  • Figure 2: Comparison of the initial and optimized designs on the $xy$-plane (left) and $yz$-plane (right).
  • Figure 3: Comparison of velocity (a) and pressure (b) on initial and optimized designs.
  • Figure 4: Comparison of the experimentally measured separation efficiency (a) and wet pressure drop (b) of the original RP9M-3D and the optimized version.

Theorems & Definitions (2)

  • Remark 2.1
  • Remark 3.1