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Master’s Dissertation Defense Carlos M. Teixeira Supervisors: Prof. José Carlos Lopes Eng. Matthieu Rolland Direct Numerical Simulation of Fixed-Bed Reactors:

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Presentation on theme: "Master’s Dissertation Defense Carlos M. Teixeira Supervisors: Prof. José Carlos Lopes Eng. Matthieu Rolland Direct Numerical Simulation of Fixed-Bed Reactors:"— Presentation transcript:

1 Master’s Dissertation Defense Carlos M. Teixeira Supervisors: Prof. José Carlos Lopes Eng. Matthieu Rolland Direct Numerical Simulation of Fixed-Bed Reactors: Effect of Random Packing 17 th July 2013

2 2 Outline FEUP/IFPEN Direct Numerical Simulation of Fixed-Bed Reactors: Effect of Random Packing  Introduction  Objectives  State of the Art  Methodology  Results and Discussion  Conclusions

3 3 Introduction FEUP/IFPEN Direct Numerical Simulation of Fixed-Bed Reactors: Effect of Random Packing

4 4 Introduction FEUP/IFPEN Direct Numerical Simulation of Fixed-Bed Reactors: Effect of Random Packing Reactors with low tube-to-particle diameter ratio  Pseudo Homogeneous Models may not be valid  Local Phenomena are dominant  Wall Effect  Packing Effect

5 5 Introduction FEUP/IFPEN Direct Numerical Simulation of Fixed-Bed Reactors: Effect of Random Packing Example of Packing Effect Problem Description  Packing of eight cylinders with different arrangements  Fluid with zero concentration at the inlet flows through the packing  Laminar regime  Cylinders with constant concentration in their surface  Transfer solute to the fluid Normalized outlet concentration for the different arrangements

6 6 Outline FEUP/IFPEN Direct Numerical Simulation of Fixed-Bed Reactors: Effect of Random Packing  Introduction  Objectives  State of the Art  Methodology  Results and Discussion  Conclusions

7 7 Objectives FEUP/IFPEN Direct Numerical Simulation of Fixed-Bed Reactors: Effect of Random Packing  Study the phenomena of single phase fluid flow through fixed-bed reactors at low particle Reynolds number  Understand how the packing structure affects the flow

8 8 Outline FEUP/IFPEN Direct Numerical Simulation of Fixed-Bed Reactors: Effect of Random Packing  Introduction  Objectives  State of the Art  Methodology  Results and Discussion  Conclusions

9 9 State of the Art FEUP/IFPEN Direct Numerical Simulation of Fixed-Bed Reactors: Effect of Random Packing CFD Simulation of Fixed-Bed Reactors

10 10 State of the Art FEUP/IFPEN Direct Numerical Simulation of Fixed-Bed Reactors: Effect of Random Packing  Coupling between Hydrodynamics, Heat Transfer and Chemical Reaction:  Less works on the literature  Applied in small size problems (dozens of particles)  Particle shape: mostly spheres CFD Simulation of Fixed-Bed Reactors

11 11 Outline FEUP/IFPEN Direct Numerical Simulation of Fixed-Bed Reactors: Effect of Random Packing  Introduction  Objectives  State of the Art  Methodology  Results and Discussion  Conclusions

12 12 Methodology FEUP/IFPEN Direct Numerical Simulation of Fixed-Bed Reactors: Effect of Random Packing Coupling between DEM and CFD  GRAINS3D (Packing Simulation)  PeliGRIFF (Fluid Flow Simulation)

13 13 Methodology FEUP/IFPEN Direct Numerical Simulation of Fixed-Bed Reactors: Effect of Random Packing Grid Refinement Studies Relative error in the inlet velocity as a function of the grid resolution (ε=0.799, l/d p =1)

14 14 Outline FEUP/IFPEN Direct Numerical Simulation of Fixed-Bed Reactors: Effect of Random Packing  Introduction  Objectives  State of the Art  Methodology  Results and Discussion  Conclusions

15 15 Results and Discussion FEUP/IFPEN Direct Numerical Simulation of Fixed-Bed Reactors: Effect of Random Packing Flow through Structured Packed Beds  Unit cell approach A packed bed of simple cubic arrangement of spheres. a) Unit cell b) Alternative representation of a simple cubic unit cell. (a) (b)

16 16 Results and Discussion FEUP/IFPEN Direct Numerical Simulation of Fixed-Bed Reactors: Effect of Random Packing Flow through Structured Packed Beds of Spheres  Validation Case Comparison between the simulated dimensionless pressure drop and results from Hill et al. (2001) for a dilute array of spheres (ε=0.799)

17 17 Results and Discussion FEUP/IFPEN Direct Numerical Simulation of Fixed-Bed Reactors: Effect of Random Packing  Effect of cylinder orientation Effect of cylinders orientation on dimensionless pressure drop (ε=0.799, l/d p =1) Flow through Structured Packed Beds of Cylinders

18 18 Results and Discussion FEUP/IFPEN Direct Numerical Simulation of Fixed-Bed Reactors: Effect of Random Packing  Transition from laminar regime to unsteady and chaotic flow Flow through Structured Packed Beds of Cylinders Particle Reynolds number as a function of time for 45º orientation (ΔP=10 Pa)

19 19 Results and Discussion FEUP/IFPEN Direct Numerical Simulation of Fixed-Bed Reactors: Effect of Random Packing Flow through Randomly Packed Beds of Cylinders Case ID FBR1 FBR2 FBR3 Nº of particles Porosity, ε

20 20 Results and Discussion FEUP/IFPEN Direct Numerical Simulation of Fixed-Bed Reactors: Effect of Random Packing Flow through Randomly Packed Beds of Cylinders  Simulated Packed Beds

21 21 Results and Discussion FEUP/IFPEN Direct Numerical Simulation of Fixed-Bed Reactors: Effect of Random Packing Flow through Randomly Packed Beds of Cylinders  Pressure Drop Dimensionless pressure drop as a function of porosity. Comparison between simulations and Ergun correlation predictions (Re dp =1).

22 22 Results and Discussion FEUP/IFPEN Direct Numerical Simulation of Fixed-Bed Reactors: Effect of Random Packing Flow through Randomly Packed Beds of Cylinders  Spatial Velocity Distribution Three different zones are identified:  Recirculation zones in the packing top and bottom and in the wake of the particles (with negative velocities)  High velocity zones where the void fraction is small and the velocity increases up to a factor of 15  Low velocity zones near the particles surfaces

23 23 Results and Discussion FEUP/IFPEN Direct Numerical Simulation of Fixed-Bed Reactors: Effect of Random Packing Flow through Randomly Packed Beds of Cylinders  Statistical Velocity Distribution Probability density functions of normalized z-velocity in different zones of the fixed-bed.

24 24 Results and Discussion FEUP/IFPEN Direct Numerical Simulation of Fixed-Bed Reactors: Effect of Random Packing Flow through Randomly Packed Beds of Cylinders  Statistical Velocity Distribution (link with porosity) Inlet Outlet Axial average porosity profile

25 25 Results and Discussion FEUP/IFPEN Direct Numerical Simulation of Fixed-Bed Reactors: Effect of Random Packing Flow through Randomly Packed Beds of Cylinders  Statistical Velocity Distribution (link with porosity)

26 26 Results and Discussion FEUP/IFPEN Direct Numerical Simulation of Fixed-Bed Reactors: Effect of Random Packing Flow through Randomly Packed Beds of Cylinders  Statistical Velocity Distribution

27 27 Outline FEUP/IFPEN Direct Numerical Simulation of Fixed-Bed Reactors: Effect of Random Packing  Introduction  Objectives  State of the Art  Methodology  Results and Discussion  Conclusions

28 28 Conclusions FEUP/IFPEN Direct Numerical Simulation of Fixed-Bed Reactors: Effect of Random Packing Flow through Structured Packed Beds

29 29 Conclusions FEUP/IFPEN Direct Numerical Simulation of Fixed-Bed Reactors: Effect of Random Packing Flow through Randomly Packed Beds  Good agreement between Ergun’s pressure drop predictions and simulation results were found  Velocity distributions were analyzed and three different zones were identified  Velocity distributions appear to follow the average local porosity: the length to establish the flow is identical to the length to establish the porosity

30 30 FEUP/IFPEN Direct Numerical Simulation of Fixed-Bed Reactors: Effect of Random Packing Thank you for your attention


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