1. Summary of the Numerical Simulation Project Conducted in
NBIL By Yashar Seyed Vahedein 03/19/2015
2. Produce New Cell Tools Template based manufacturing CVD
Experiment CVD Simulation Fabricating CNTs with higher efficiency
Need for template based manufacturing of CNTs Output of the process
NBIL Inlet Gasses AAO Template Furnace Dimensions Temperature and
Flow rate Predict CNT manufacturing process designed by NBIL Lab
Motivations: Control the process and the effect of the parameters
on deposition. Save time and resources by simulating the process
Create a universal method to be used by others for TB-CVD (not
currently available in literature) Diagram of the Driving Needs,
Process and Outcome of TB-CVD INPUTS NBIL Single cell analysis
Electrical,Bio,nano, Mechanical app. High conductivity&
strength 2
3. Schematics of the Template Based-CVD Setup in NBIL 1. NBIL:
Nano Bio Interface Laboratory Exhaust Heated region Heater Heater
F.MPrecursorgas Carriergas Temperature knobs Position of the
templates Carbon deposited in a template Carrier gas: Ethylene
Helium (Mixture) Precursor gas: Argon Experimentally Observed
change in Deposition due to the Increase in Flow Rate M. Golshadi,
J. Maita, D. Lanza, M. Zeiger, V. Presser, and M. G. Schrlau,
Effects of synthesis parameters on carbon nanotubes manufactured by
template-based chemical vapor deposition, Carbon, vol. 80, pp.
2839, Dec. 2014. 3
4. Defining the Boundary Conditions based on Physical system
Heated Walls Inlet flow temperature = 300k Inlet Flow rates: 20 to
300 sccm No slip condition on tube wall and templates = 0 1 = 6680
1 = 6880 1 = 6680 = 0 = 0 = 0 5 304.8 mm 3.88mm 4.88mm 72.3mm 2
13mm 4mm 6.8mm Static gauge pressure in the outlet = 0 4
5. Formulation of the problem in CFD with conservation
equations (Navier stokes approach) Generalized Source term
(constant and linear) Generalized diffusion coefficient Generalized
Transport Variable By taking divergence of these two, they can be
transformed into volume integrals. + . = . + Rate of increase of
mole of the species Net rate of additions of mole of the species
per unit volume by convection Molar-averaged velocity Net rate of
mole of the species per unit volume by diffusion in a binary system
of components, otherwise xa is replaced by The molar rate of
production of species by chemical reaction = = =1 If the number of
chemical reactions taking place in the system is , the mass
production rate is: stoichiometric coefficient Difference between
the forward and backward reactions Fluent solves the differential
form of this equation: 5
6. Approach to Solve this Problem This numerical problem is
solved using: Compressible laminar flow. Temperature dependent
Ideal gas. Consumption of species on templates . Mixture of
Ethylene helium entering from the inlet into a bed of residual
argon. Steady state formulation is used based on a validation
process using 2D transient solution. Pressure-based solver with a
coupled pressure-velocity coupling is utilized. 6
7. Comparing results from 2D and 3D model to choose how to best
represent the system 0.150.100.050.00-0.05-0.10-0.15 690 680 670
660 650 Position from middle of tube furnace [m] Temprature[C]
Temperature Vs Length - 25.4 mm Above Bottom Wall Temperature Vs
Length - 38.1 mm Above Bottom Wall Temperature Vs Length - 25.4 mm
Above Bottom Wall(simulation) Temperature Vs Length - 38.1 mm Above
Bottom Wall(simulation) 0.02m Area in vicinity of templates
Comparison of Temperature along the Heated Region Simulation Vs.
Experiment 20 mm 300 mm 3D 150 mm 100 mm100 mm [m/s][K] 2D 3D
Streamlines in the middle cross section and along the tube
Temperature Contour Plots Velocity Vectors Constant Temperature
Velocity Vectors 7
8. Tube Membranes 60 SCCM Membranes 60 SCCM Recirculation on
lower flow rates, cause better mixing CVD Tube Furnace Schematics
Velocity Vectors for 60 SCCM Flow rate Contour plots of (Ethylene),
Velocity Vectors and an Animation Showing Transient Concentration
Profile Evolving Through Time Mass fraction will be related to the
reaction rate 3.00e-01 2.94e-01 2.88e-01 2.81e-01 2.75e-01 2.69e-01
2.63e-01 2.56e-01 2.50e-01 2.44e-01 2.38e-01 2.31e-01 2.25e-01
2.19e-01 2.13e-01 2.06e-01 2.00e-01 1.94e-01 1.88e-01 1.81e-01
1.75e-01 1.69e-01 1.63e-01 1.56e-01 1.50e-01 1.44e-01 1.38e-01
1.31e-01 1.25e-01 1.19e-01 1.13e-01 1.06e-01 1.00e-1 9.38e-02
8.75e-02 8.13e-02 7.50e-02 6.88e-02 6.25e-02 5.63e-02 5.00e-02
Evolving Mass fraction conditions 8
9. Results for mass fraction and velocity distribution
30020010080604020 0.0100 0.0075 0.0050 0.0025 0.0000
u-velocity(m/s) Boxplot of u-velocity - flow rate range from 20 to
300 sccm Flow rates (sccm) Uvelocity(m/s) Contours of Axial,
Vertical and transverse Velocity components Mass Fraction
Distribution (Left) and Velocity Vectors (Right) for Different Flow
rates 9
10. Line-Averaged Mass Fraction Vs. Flow rate on the Midline
Passing Through two Templates 0.12 0.125 0.13 0.135 0.14 0.145 0.15
0.155 0 50 100 150 200 250 300 350 MassFractionofEthylene Flow rate
[SCCM] 20-300 10
11. Mass Fraction Evolution Video for 60 sccm Flow Rate 11