scholarly journals Particle-Resolved Computational Fluid Dynamics as the Basis for Thermal Process Intensification of Fixed-Bed Reactors on Multiple Scales

Energies ◽  
2021 ◽  
Vol 14 (10) ◽  
pp. 2913
Author(s):  
Nico Jurtz ◽  
Urvashi Srivastava ◽  
Alireza Attari Moghaddam ◽  
Matthias Kraume
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Heat Transport ◽  
Multiple Scales ◽  
Plug Flow ◽  
Fixed Bed ◽  
Process Intensification ◽  
Transport Parameters ◽  
Flow Models ◽  
Fixed Bed Reactors

Process intensification of catalytic fixed-bed reactors is of vital interest and can be conducted on different length scales, ranging from the molecular scale to the pellet scale to the plant scale. Particle-resolved computational fluid dynamics (CFD) is used to characterize different reactor designs regarding optimized heat transport characteristics on the pellet scale. Packings of cylinders, Raschig rings, four-hole cylinders, and spheres were investigated regarding their impact on bed morphology, fluid dynamics, and heat transport, whereby for the latter particle shape, the influence of macroscopic wall structures on the radial heat transport was also studied. Key performance indicators such as the global heat transfer coefficient and the specific pressure drop were evaluated to compare the thermal performance of the different designs. For plant-scale intensification, effective transport parameters that are needed for simplified pseudo-homogeneous two-dimensional plug flow models were determined from the CFD results, and the accuracy of the simplified modeling approach was judged.

scholarly journals Workflow for computational fluid dynamics modeling of fixed‐bed reactors packed with metal foam pellets: Hydrodynamics

AIChE Journal ◽  
2021 ◽  
Author(s):  
Ginu R. George ◽  
Marina Bockelmann ◽  
Leonhard Schmalhorst ◽  
Didier Beton ◽  
Alexandra Gerstle ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Metal Foam ◽  
Fixed Bed ◽  
Dynamics Modeling ◽  
Computational Fluid Dynamics Modeling ◽  
Fixed Bed Reactors

Kinetics and computational fluid dynamics study for Fischer–Tropsch synthesis in microchannel and fixed-bed reactors

2018 ◽  
Vol 3 (3) ◽  
pp. 319-332 ◽  
Author(s):  
Aditya Rai ◽  
Mohit Anand ◽  
Saleem A. Farooqui ◽  
Malayil G. Sibi ◽  
Anil K. Sinha
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Concentration Profile ◽  
Fixed Bed ◽  
Tropsch Synthesis ◽  
Fischer Tropsch ◽  
Fischer Tropsch Synthesis ◽  
Fixed Bed Reactors ◽  
Co Concentration

CO concentration profile during Fischer–Tropsch synthesis in microchannel and fixed bed reactors.

Degradation of chlorophenols by biofilms on semi-permeable membranes in two types of fixed bed reactors

1995 ◽  
Vol 32 (8) ◽  
pp. 205-212 ◽  
Author(s):  
A. Wobus ◽  
S. Ulrich ◽  
I. Röske
Keyword(s):  
Continuous Flow ◽  
Plug Flow ◽  
Fixed Bed ◽  
Biofilm Reactor ◽  
Flow Conditions ◽  
Concentration Gradients ◽  
Batch Mode ◽  
Sequencing Batch Biofilm Reactor ◽  
Fixed Bed Reactors ◽  
Protozoan Community

Two identical fixed bed reactors containing gas-permeable tubings as carrier material were compared for the elimination of chlorophenols. Under plug flow conditions, the continuous flow operation resulted in a stratification of biomass due to concentration gradients. To achieve a homogeneous colonization, the sequencing batch mode has been applicated to one biofilm reactor (Sequencing Batch Biofilm Reactor - SBBR). Concentration gradients after filling, probably due to sorption phenomena, caused an uneven distribution of biomass in the SBBR. However, the colonization of the SBBR was more homogeneous as compared to the continuously operated reactor (CFBR). As to the elimination of a trichlorophenol (2,4,5-trichlorophenol - TCP), no significant differences between the SBBR and the CFBR were observed with regard to its sensitivity against load surges. It is to be supposed that sorption to the biofilm was included in the elimination of chlorophenols. A higher diversity of protozoan community and meiofauna is obviously to be attributed to continuous flow.

Verification Benchmarks to Assess the Implementation of Computational Fluid Dynamics Based Hemolysis Prediction Models

2015 ◽  
Vol 137 (9) ◽  
Author(s):  
Prasanna Hariharan ◽  
Gavin D’Souza ◽  
Marc Horner ◽  
Richard A. Malinauskas ◽  
Matthew R. Myers
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Power Law ◽  
Analytical Solutions ◽  
Experimental Validation ◽  
Cfd Simulations ◽  
Flow Models ◽  
Flow Acceleration ◽  
Blood Damage ◽  
Eulerian Models

As part of an ongoing effort to develop verification and validation (V&V) standards for using computational fluid dynamics (CFD) in the evaluation of medical devices, we have developed idealized flow-based verification benchmarks to assess the implementation of commonly cited power-law based hemolysis models in CFD. The verification process ensures that all governing equations are solved correctly and the model is free of user and numerical errors. To perform verification for power-law based hemolysis modeling, analytical solutions for the Eulerian power-law blood damage model (which estimates hemolysis index (HI) as a function of shear stress and exposure time) were obtained for Couette and inclined Couette flow models, and for Newtonian and non-Newtonian pipe flow models. Subsequently, CFD simulations of fluid flow and HI were performed using Eulerian and three different Lagrangian-based hemolysis models and compared with the analytical solutions. For all the geometries, the blood damage results from the Eulerian-based CFD simulations matched the Eulerian analytical solutions within ∼1%, which indicates successful implementation of the Eulerian hemolysis model. Agreement between the Lagrangian and Eulerian models depended upon the choice of the hemolysis power-law constants. For the commonly used values of power-law constants (α  = 1.9–2.42 and β  = 0.65–0.80), in the absence of flow acceleration, most of the Lagrangian models matched the Eulerian results within 5%. In the presence of flow acceleration (inclined Couette flow), moderate differences (∼10%) were observed between the Lagrangian and Eulerian models. This difference increased to greater than 100% as the beta exponent decreased. These simplified flow problems can be used as standard benchmarks for verifying the implementation of blood damage predictive models in commercial and open-source CFD codes. The current study used only a power-law model as an illustrative example to emphasize the need for model verification. Similar verification problems could be developed for other types of hemolysis models (such as strain-based and energy dissipation-based methods). And since the current study did not include experimental validation, the results from the verified models do not guarantee accurate hemolysis predictions. This verification step must be followed by experimental validation before the hemolysis models can be used for actual device safety evaluations.

Advances in fixed-bed reactor modeling using particle-resolved computational fluid dynamics (CFD)

2019 ◽  
Vol 35 (2) ◽  
pp. 139-190 ◽  
Author(s):  
Nico Jurtz ◽  
Matthias Kraume ◽  
Gregor D. Wehinger
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Fixed Bed ◽  
Review Article ◽  
Catalyst Design ◽  
Fixed Bed Reactor ◽  
Reactor Modeling ◽  
Catalytic Systems ◽  
Heterogeneous Catalytic ◽  
Computational Fluid Dynamics Cfd

Abstract In 2006, Dixon et al. published the comprehensive review article entitled “Packed tubular reactor modeling and catalyst design using computational fluid dynamics.” More than one decade later, many researchers have contributed to novel insights, as well as a deeper understanding of the topic. Likewise, complexity has grown and new issues have arisen, for example, by coupling microkinetics with computational fluid dynamics (CFD). In this review article, the latest advances are summarized in the field of modeling fixed-bed reactors with particle-resolved CFD, i.e. a geometric resolution of every pellet in the bed. The current challenges of the detailed modeling are described, i.e. packing generation, meshing, and solving with an emphasis on coupling microkinetics with CFD. Applications of this detailed approach are discussed, i.e. fluid dynamics and pressure drop, dispersion, heat and mass transfer, as well as heterogeneous catalytic systems. Finally, conclusions and future prospects are presented.

Particle Image Velocimetry and Computational Fluid Dynamics Analysis of Fuel Cell Manifold

2010 ◽  
Vol 7 (3) ◽  
Author(s):  
Jesper Lebæk ◽  
Marcin Blazniak Andreasen ◽  
Henrik Assenholm Andresen ◽  
Mads Bang ◽  
Søren Knudsen Kær
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Particle Image Velocimetry ◽  
Fuel Cell ◽  
Particle Image ◽  
High Current Density ◽  
Plug Flow ◽  
Flow Distribution ◽  
Image Velocimetry ◽  
Computational Fluid Dynamics Analysis

The inlet effect on the manifold flow in a fuel cell stack was investigated by means of numerical methods (computational fluid dynamics) and experimental methods (particle image velocimetry). At a simulated high current density situation the flow field was mapped on a 70 cell simulated cathode manifold. Three different inlet configurations were tested: plug flow, circular inlet, and a diffuser inlet. A very distinct jet was formed in the manifold, when using the circular inlet configuration, which was confirmed both experimentally and numerically. This jet was found to be an asymmetric confined jet, known as the symmetry-breaking bifurcation phenomenon, and it is believed to cause a significant maldistribution of the stack flow distribution. The investigated diffuser design proved to generate a much smoother transition from the pipe flow to the manifold flow with a subsequent better flow distribution. A method was found in the literature to probe if there is a risk of jet asymmetry; it is however recommended by the author to implement a diffuser design, as this will generate better stack flow distribution and less head loss. Generally, the numerical and experimental results were found in to be good agreement, however, a detailed investigation revealed some difference in the results.

scholarly journals COMPUTATIONAL FLUID DYNAMICS STUDY OF PULL AND PLUG FLOW BOUNDARY CONDITION ON NASAL AIRFLOW

2013 ◽  
Vol 25 (04) ◽  
pp. 1350044 ◽  
Author(s):  
Mohammed Zubair ◽  
Vizy Nazira Riazuddin ◽  
Mohammad Zulkifly Abdullah ◽  
Ismail Rushdan ◽  
Ibrahim Lutfi Shuaib ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Boundary Condition ◽  
Computational Fluid Dynamics ◽  
Boundary Conditions ◽  
Comparative Study ◽  
Flow Model ◽  
Plug Flow ◽  
Maximum Velocity ◽  
Nasal Valve ◽  
Flow Boundary

The recent advances in the computer based computational fluid dynamics (CFD) software tools in the study of airflow behavior in the nasal cavity have opened an entirely new field of medical research. This numerical modeling method has provided both engineers and medical specialists with a clearer understanding of the physics associated with the flow in the complicated nasal domain. The outcome of any CFD investigation depends on the appropriateness of the boundary conditions applied. Most researchers have employed plug boundary condition as against the pull flow which closely resembles the physiological phenomenon associated with the breathing mechanism. A comparative study on the effect of using the plug and pull flow boundary conditions are evaluated and their effect on the nasal flow are studied. Discretization error estimation using Richardson's extrapolation (RE) method has also been carried out. The study is based on the numerical model obtained from computed tomographic data of a healthy Malaysian subject. A steady state Reynold averaged Navier–Stokes and continuity equations is solved for inspiratory flow having flow rate 20 L/min representing turbulent boundary conditions. Comparative study is made between the pull and plug flow model. Variation in flow patterns and flow features such as resistance, pressure and velocity are presented. At the nasal valve, the resistance for plug flow is 0.664 Pa-min/L and for pull flow the value is 0.304 Pa-min/L. The maximum velocity at the nasal valve is 3.28 m/s for plug flow and 3.57 m/s for pull flow model.

scholarly journals Computational Fluid Dynamics Modeling of the Fuel Reactor in NETL's 50 kWth Chemical Looping Facility

2017 ◽  
Vol 139 (4) ◽  
Author(s):  
Ronald W. Breault ◽  
Justin Weber ◽  
Doug Straub ◽  
Sam Bayham
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Oxygen Carrier ◽  
Fixed Bed ◽  
Nucleation And Growth ◽  
Chemical Looping ◽  
Gravimetric Analysis ◽  
Oxygen Carriers ◽  
Dynamics Modeling ◽  
Fuel Reactor

The National Energy Technology Laboratory (NETL) has explored chemical looping in its 50 kWth facility using a number of oxygen carriers. In this work, the results for methane conversion in the fuel reactor with a hematite iron ore as the oxygen carrier are analyzed. The experimental results are compared to predictions using CPFD's barracuda computational fluid dynamics (CFD) code with kinetics derived from the analysis of fixed bed data. It has been found through analytical techniques from thermal gravimetric analysis data as well as the same fixed bed data that the kinetics for the methane–hematite reaction follows a nucleation and growth or Johnson–Mehl–Avrami (JMA) reaction mechanism. barracuda does not accept nucleation and growth kinetics; however, there is enough sufficient variability of the solids dependence within the software such that the nucleation and growth behavior can be mimicked. This paper presents the method to develop the pseudo-JMA kinetics for barracuda extracted from the fixed bed data and then applies these values to the fuel reactor data to compare the computational results to experimental data obtained from 50 kWth unit for validation. Finally, a fuel reactor design for near complete conversion is proposed.

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