Development of a CFD simulation environment for the determination of characteristic stress parameters in an extrusion device

1. Development of a CFD simulation environment for
the determination of characteristic stress
parameters in an extrusion device
Hafiz Muhammad Shahzaib Raza, Study Thesis, 31/10/19

2. 31.10.2019 | Hafiz Muhammad Shahzaib Raza | CFD simulation environment of an extrusion device | Slide 2
Motivation
[1] Jelle Smekens et al: “Influence of Electrode Density on the Performance of Li-Ion Batteries”, 2016
[1]
Slurry
preparation
Coating &
drying
Calendering
Cutting
electrodes
Cell
assembly
Electrolytes
filling &
formation
Slurry
preparation

3. 31.10.2019 | Hafiz Muhammad Shahzaib Raza | CFD simulation environment of an extrusion device | Slide 3
Dispersion process
 The production of electrodes is achieved with the dispersion process.
Wetting Dispersing Stabilisation
[2]
[2] According to Jochum Beetsma: “The Differences Between Wetting Agents and Dispersants”, 2015
Dispersing

4. 31.10.2019 | Hafiz Muhammad Shahzaib Raza | CFD simulation environment of an extrusion device | Slide 4
Extrusion device
 Dispersing process is carried out with the help of an extruder.
 Dispersive mixing is achieved with high shear rate.
[3]
[3] G. Angadi et al. “Effect of screw configuration on the dispersion of nanofillers”, 2017
High shear mixing

5. 31.10.2019 | Hafiz Muhammad Shahzaib Raza | CFD simulation environment of an extrusion device | Slide 5
Kneading element and degree of filling
𝑉𝑖𝑛𝑙𝑒𝑡 = 0.034𝑙/𝑚𝑖𝑛Degree of filling: 70%
𝑉𝑜𝑢𝑡𝑙𝑒𝑡
ω

6. 31.10.2019 | Hafiz Muhammad Shahzaib Raza | CFD simulation environment of an extrusion device | Slide 6
600 rpm
Simulation setup
120 rpm
Fine mesh
Coarse mesh
High viscosity
Low viscosity
High viscosity
Low viscosity
600 rpm

7. 31.10.2019 | Hafiz Muhammad Shahzaib Raza | CFD simulation environment of an extrusion device | Slide 7
Animation of the flow
 The flow of the slurry in an extruder element.

8. 31.10.2019 | Hafiz Muhammad Shahzaib Raza | CFD simulation environment of an extrusion device | Slide 8
Basic steps in CFD
 The basic steps for a CFD simulation process are:
Pre-processing Solver Post processing
[4]
[4] According to H K Versteeg: “An Introduction to Computational Fluid Dynamics. THE FINITE VOLUME METHOD”, 2007
 Geometry
 Mesh
 Physics
 Solver setting
 Compute solution  Examine results

9. 31.10.2019 | Hafiz Muhammad Shahzaib Raza | CFD simulation environment of an extrusion device | Slide 9
Residuals and courant number
 Residuals are defined as:
 Imbalance of conserved variable in a control volume.
 Difference between actual and theoretical solution.
 Courant number is defined as:
[5]
[5] According to Christopher J. Greenshields: “OpenFOAM. The OpenFOAM Foundation. User Guide”, 2018
𝛿𝑥
𝑈
1.0x10-5
[5]

10. 31.10.2019 | Hafiz Muhammad Shahzaib Raza | CFD simulation environment of an extrusion device | Slide 10
Residuals
 High residuals means unstable simulations.

11. 31.10.2019 | Hafiz Muhammad Shahzaib Raza | CFD simulation environment of an extrusion device | Slide 11
Courant number
 The flow is transient but every cell is solved as steady state.

12. 31.10.2019 | Hafiz Muhammad Shahzaib Raza | CFD simulation environment of an extrusion device | Slide 12
Execution time of the simulations
 The number of cells in fine mesh is increased by 15%
83%

13. 31.10.2019 | Hafiz Muhammad Shahzaib Raza | CFD simulation environment of an extrusion device | Slide 13
High shear regions in an extruder
There are some region in the twin
screw element where the shear rate is
high.
 The high shear regions are:
 Upper lobal pool
 Lower lobal pool.
[6] According to Martin, C.: “Twin Screw Extruders as Continuous Mixers for Thermal Processing: a Technical and Historical Perspective. ”, 2016
[6]

14. 31.10.2019 | Hafiz Muhammad Shahzaib Raza | CFD simulation environment of an extrusion device | Slide 14
Velocity magnitude
 The region of maximum velocity.

15. 31.10.2019 | Hafiz Muhammad Shahzaib Raza | CFD simulation environment of an extrusion device | Slide 15
High shear regions in an extruder element
 The high shear region of a single element.

16. 31.10.2019 | Hafiz Muhammad Shahzaib Raza | CFD simulation environment of an extrusion device | Slide 16
Shear rates
 Shear rate distribution with rotational speed of 120 rpm.
6.0x104 s-1

17. 31.10.2019 | Hafiz Muhammad Shahzaib Raza | CFD simulation environment of an extrusion device | Slide 17
Shear rates
 Shear rate distribution with rotational speed of 600 rpm.
5.3x105 s-1

18. 31.10.2019 | Hafiz Muhammad Shahzaib Raza | CFD simulation environment of an extrusion device | Slide 18
Shear rates 120 rpm vs 600 rpm
Direct comparison between shear rates.
 The maximum shear rates of both cases
are compared.
 500 % increase in rotational speed.
 527 % increase in shear rate.

19. 31.10.2019 | Hafiz Muhammad Shahzaib Raza | CFD simulation environment of an extrusion device | Slide 19
Shear stress
 Shear stress in case with 120 rpm:
5.6x105 Pa
[7]
[7] Bröckel, U. et al.: “Product Design and Engineering. Formulation of Gels and Pastes. ”, 2013

20. 31.10.2019 | Hafiz Muhammad Shahzaib Raza | CFD simulation environment of an extrusion device | Slide 20
Shear stress
 The shear stress in case of 600 rpm.
1.75x106 Pa

21. 31.10.2019 | Hafiz Muhammad Shahzaib Raza | CFD simulation environment of an extrusion device | Slide 21
Shear stress 120 rpm vs 600 rpm
Direct comparison between shear stress.
 The maximum shear stresses of both
cases are compared.
 500 % increase in rotational speed.
 205 % increase in shear stress.

22. 31.10.2019 | Hafiz Muhammad Shahzaib Raza | CFD simulation environment of an extrusion device | Slide 22
Conclusions and outlook
 The simulation time of fine meshes are greater than the coarse meshes.
 The shear rate and stress produced with 600 rpm is high as compared to the rotational
speed of 120 rpm.
 The dispersing will be slightly high in high viscous slurries.
 High dispersive mixing will be achieved with high rotational speed.
 The results of fine meshes are more accurate and refined as compared to the coarse
mesh.
 The viscosity plays an important role in the dispersing process.
 For high rotational speed, mesh should be:
 Adjusted.
 Refined where fluctuations are high.

23. Development of a CFD simulation environment for
the determination of characteristic stress
parameters in an extrusion device
Hafiz Muhammad Shahzaib Raza, Study Thesis, 31/10/19