Multiscale Modeling of Carbon Nanotube Bundle Agglomeration inside a Gas Phase Pyrolysis Reactor

MRS Advances ◽  
2017 ◽  
Vol 2 (48) ◽  
pp. 2621-2626 ◽  
Author(s):  
Guangfeng Hou ◽  
Vianessa Ng ◽  
Chenhao Xu ◽  
Lu Zhang ◽  
Guangqi Zhang ◽  
...  
Keyword(s):  
Carbon Nanotube ◽  
Gas Phase ◽  
Gas Flow ◽  
Flow Analysis ◽  
Multiscale Model ◽  
Discrete Phase Modeling ◽  
Discrete Phase ◽  
Computational Fluid Dynamics Cfd ◽  
Pyrolysis Reactor ◽  
Nanotube Bundle

ABSTRACTCarbon nanotube (CNT) sock formation is required for the continuous synthesis of CNT thread or sheet using the gas phase pyrolysis method. Nanometer diameter CNTs form and are carried along the reactor tube by gas flow. During the flow, the CNT stick to each other and form bundles of about 10-100 nm diameter. Coupling of the CNT bundles in the flow leads to the formation of a centimeter diameter CNT sock with a wall that is hundreds of nanometers thick. Understanding the multiscale phenomena of sock formation is vital for optimizing the CNT synthesis and manufacturing process. In this work, we present a multiscale model for the CNT bundle agglomeration inside a horizontal gas phase pyrolysis reactor. The interaction between CNT bundles was analyzed by representing the attraction forces between CNTs using a discrete phase modeling method. Flow in the synthesis reactor was studied using a computational fluid dynamics (CFD) technique with multiphase flow analysis. A model was proposed to represent the coupling between CNT bundles and the gas flow. The effect of different CNT bundles on the agglomeration phenomenon was analyzed. The modeling results were also compared with experimental observations.

scholarly journals Comparative Assessment of In Vitro and In Silico Methods for Aerodynamic Characterization of Powders for Inhalation

Pharmaceutics ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 1831
Author(s):  
Jelisaveta Ignjatović ◽  
Tijana Šušteršič ◽  
Aleksandar Bodić ◽  
Sandra Cvijić ◽  
Jelena Đuriš ◽  
...  
Keyword(s):  
In Silico ◽  
Aerodynamic Performance ◽  
Dry Powders ◽  
In Vitro Methods ◽  
Discrete Phase Modeling ◽  
Discrete Phase ◽  
Computational Fluid Dynamics Cfd ◽  
In Silico Methods

In vitro assessment of dry powders for inhalation (DPIs) aerodynamic performance is an inevitable test in DPI development. However, contemporary trends in drug development also implicate the use of in silico methods, e.g., computational fluid dynamics (CFD) coupled with discrete phase modeling (DPM). The aim of this study was to compare the designed CFD-DPM outcomes with the results of three in vitro methods for aerodynamic assessment of solid lipid microparticle DPIs. The model was able to simulate particle-to-wall sticking and estimate fractions of particles that stick or bounce off the inhaler’s wall; however, we observed notable differences between the in silico and in vitro results. The predicted emitted fractions (EFs) were comparable to the in vitro determined EFs, whereas the predicted fine particle fractions (FPFs) were generally lower than the corresponding in vitro values. In addition, CFD-DPM predicted higher mass median aerodynamic diameter (MMAD) in comparison to the in vitro values. The outcomes of different in vitro methods also diverged, implying that these methods are not interchangeable. Overall, our results support the utility of CFD-DPM in the DPI development, but highlight the need for additional improvements in these models to capture all the key processes influencing aerodynamic performance of specific DPIs.

Multiphysics, Multiphase Modeling of Carbon Nanotube Synthesis Process by Chemical Vapor Deposition

2007 ◽  
Author(s):  
Mahmoud Reza Hosseini ◽  
Nader Jalili
Keyword(s):  
Chemical Vapor Deposition ◽  
Carbon Nanotube ◽  
Gas Phase ◽  
Production Rate ◽  
Flow Rate ◽  
Vapor Deposition ◽  
Gas Flow ◽  
Chemical Vapor ◽  
Quartz Tube ◽  
Hydrocarbon Gas

In the present paper, a comprehensive modeling framework is proposed to conduct multiphysics, multiphase modeling of carbon nanotube (CNT) fabrication process by chemical vapor deposition (CVD). The modeling is based on fluid dynamics, heat transfer, chemical reaction, as well as mass transport phenomena which have been fully coupled with each other. The inserted gasses are considered as methane (CH4) as the main hydrocarbon gas and hydrogen (H2) as the process enhancement gas. In the gas phase reaction section, a novel set of reactions for CH4 hydrocarbon gas is proposed which is based on 71 different chemical reactions that take place near CVD inlet. Also, surface reactions are modeled by considering 19 set of reactions acting near substrate surface which lead to CNTs formation. The investigation is performed for different combination of gas flow rate quantities ranging from 500 to 1000 sccm (standard cubic centimeter per minute) for methane and 250 to 500 sccm for hydrogen gas. Also, the quartz tube temperature is considered to change from 700 to 1000 °C. Since the thermal specifications for each species are calculated individually, the gas flow inside the quartz tube is treated as nonisothermal flow. Numerous simulations are conducted and the results are compared with the fabricated CNT’s images taken by the SEM (scanning electron microscopy). Utilizing the obtained diagrams from modeling, the effects caused by gas mixture flow rate and temperature changes on the production rate of gas phase species such as H, CH3, C2H2 and bulk carbon species (C and 2C) that produced by surface species TC and TC2 are investigated. It is found that increasing the fabricated temperature causes a rise in species production rate. However, it is observed that the produced species respond differently to any change in hydrogen and hydrocarbon flow rates. The velocity, temperature profile as well as concentration distribution along the silicon substrate length have been also investigated. This study can lead to a controlled CNTs manufacturing process when combined with in-situ measurement systems.

scholarly journals Dependence of the Flue Gas Flow on the Setting of the Separation Baffle in the Flue Gas Tract

2021 ◽  
Vol 11 (7) ◽  
pp. 2961
Author(s):  
Nikola Čajová Kantová ◽  
Alexander Čaja ◽  
Marek Patsch ◽  
Michal Holubčík ◽  
Peter Ďurčanský
Keyword(s):  
Particulate Matter ◽  
Flue Gas ◽  
Gas Flow ◽  
Negative Impact ◽  
Combustion Process ◽  
Cfd Simulations ◽  
Piv Measurements ◽  
Computational Fluid Dynamics Cfd ◽  
Particle Imaging ◽  
Combustion Of Solid Fuels

With the combustion of solid fuels, emissions such as particulate matter are also formed, which have a negative impact on human health. Reducing their amount in the air can be achieved by optimizing the combustion process as well as the flue gas flow. This article aims to optimize the flue gas tract using separation baffles. This design can make it possible to capture particulate matter by using three baffles and prevent it from escaping into the air in the flue gas. The geometric parameters of the first baffle were changed twice more. The dependence of the flue gas flow on the baffles was first observed by computational fluid dynamics (CFD) simulations and subsequently verified by the particle imaging velocimetry (PIV) method. Based on the CFD results, the most effective is setting 1 with the same boundary conditions as those during experimental PIV measurements. Setting 2 can capture 1.8% less particles and setting 3 can capture 0.6% less particles than setting 1. Based on the stoichiometric calculations, it would be possible to capture up to 62.3% of the particles in setting 1. The velocities comparison obtained from CFD and PIV confirmed the supposed character of the turbulent flow with vortexes appearing in the flue gas tract, despite some inaccuracies.

Photocurrent in Carbon Nanotube Bundle: Graded Seebeck Coefficient Phenomenon

Nano Energy ◽  
2021 ◽  
pp. 106054
Author(s):  
Shen Xu ◽  
Hamidreza Zobeiri ◽  
Nicholas Hunter ◽  
Hengyun Zhang ◽  
Gyula Eres ◽  
...  
Keyword(s):  
Carbon Nanotube ◽  
Seebeck Coefficient ◽  
Nanotube Bundle

scholarly journals Atomistically informed stochastic multiscale model to predict the behavior of carbon nanotube-enhanced nanocomposites

Carbon ◽  
2015 ◽  
Vol 94 ◽  
pp. 661-672 ◽  
Author(s):  
Nithya Subramanian ◽  
Ashwin Rai ◽  
Aditi Chattopadhyay
Keyword(s):  
Carbon Nanotube ◽  
Multiscale Model

Gas flow analysis in a Kraft recovery boiler

2010 ◽  
Vol 91 (7) ◽  
pp. 789-798 ◽  
Author(s):  
D.J.O. Ferreira ◽  
M. Cardoso ◽  
S.W. Park
Keyword(s):  
Gas Flow ◽  
Flow Analysis ◽  
Recovery Boiler

Mixing Enhancement of Two Gases in a Microchannel Using DSMC

2013 ◽  
Vol 307 ◽  
pp. 166-169 ◽  
Author(s):  
Masoud Darbandi ◽  
Elyas Lakzian
Keyword(s):  
Gas Flow ◽  
Flow Analysis ◽  
Direct Simulation Monte Carlo ◽  
Equilibrium Composition ◽  
Mass Composition ◽  
Mixing Enhancement ◽  
Mixing Process ◽  
Result Section ◽  
Flow Through ◽  
Simulation Monte Carlo

Microgas flow analysis may not be performed accurately using the classical CFD methods because of encountering high Knudsen number regimes. Alternatively, the gas flow through micro-geometries can be investigated reliably using the direct simulation Monte Carlo (DSMC) method. Our concern in this paper is to use DSMC to study the mixing of two gases in a microchannel. The mixing process is assumed to be complete when the mass composition of each species deviates by no more than ±1% from its equilibrium composition. To enhance the mixing process, we focus on the effects of inlet-outlet pressure difference and the pressure ratios of the incoming CO and N2 streams on the mixing enhancement. The outcome of this study is suitably discussed in the result section.

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