Download - Piske & Wassom Summer Presentation
Studying the Mass Transport Phenomena Associated with
EvaporationGreg Wassom & Taylor Piske
Advised by Dr. Peter Kelly-Zion, Dr. Chris Pursell, and Dr. Hoa Nguyen
Details of EvaporationApplications:• Coating• Spray cooling• Printing• Surface Patterning• DNA stretching and depositingVapor Transport Mechanisms:• Diffusion and Convection
Image take from: Lin, Zhiqun. Evaporative Self-Assembly of Ordered Complex Structures. World Scientific, 2012.
Image taken from http://fe867b.medialib.glogster.com/media/18/180d72257aa1a63672899016e3dfb937691298252f3e50416f3c04d10f9ca46a/diffusion-pic-1-gif.gif
• Molecular Transport
• Driven by Concentration gradients
Buoyancy Induced Convection
Video taken from Sharma, Vidit. “VOF in Ansys Fluent 14”. https://www.youtube.com/watch?v=wys3qiBQzYY
• Bulk Transport Phenomena
• Driven by a Density Gradient
• Gravity
Experimental Techniques• Gravimetric Analysis
• Shadowgraph
• Pressure Chamber
• Schlieren Imaging
• IR Spectral Analysis0 100 200 300 400 500 600 700 800
-10
0
10
20
30
40
50
60
f(x) = − 0.108458557679504 x + 53.4299931331544R² = 0.998986998326417
Mass vs. Time
Measured Data
Fitted Slope (evaporation rate)
Linear (Fitted Slope (evaporation rate))
Time (s)
Mas
s (m
g)
SpectraMethanol
IR Spectroscopic Measurements
0 5 10 15 20 25 30 35 400.0
0.2
0.4
0.6
0.8
1.0
Hexane Methanol
Radial Position (mm)
Conc
entr
ation
/Sat
. Con
c.
Z = 1mmZ = 2 mmZ = 3 mmZ = 4 mmZ = 5 mmZ = 6 mmZ = 8 mmZ = 10 mmZ = 15 mm
Using the Experimental Conc. Data with Gridfit
• MATLAB function Gridfit models the data with a surface
• Concentration gradients ( and ) are computed along a cylindrical control volume
• Flux through the control volume is calculated
• Flux Diffusion rate
-5 0 5 10 15 20 25 30 350
5
10
15
20
r-position (mm)
z-po
sitio
n (m
m)
Analytical Methanol Data from the Weber’s Disc Model Modeled by Gridfit
Methodology Check - Comparing Methanol Diffusion Rates of Different Control Volumes
0.75 0.95 1.15 1.35 1.55 1.75 1.95 2.15 2.35 2.55 2.755.5E-08
6.0E-08
6.5E-08
7.0E-08
7.5E-08
8.0E-08
8.5E-08
9.0E-08Diffusion Rates of Methanol Using Analytical Data
Methanol TheoryCV Radius = 8.5 mmCV Radius = 8 mmCV Radius = 7.5 mm
Height of Control Volume (mm)Di
ffusi
on R
ate
(kg/
s)
Theory
Experimental Methanol Data Modeled by Gridfit
Comparing Diffusion Rates of Different Control Volumes
(Experimental Data)
0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4 2.60.0E+00
5.0E-08
1.0E-07
1.5E-07
2.0E-07
2.5E-07
Control Volume Radius = 7 mm
3MP
3MP Theory
Hexane
Hexane Theory
Methanol
Methanol Theory
Control Volume Height (mm)
Diffu
sion
Rat
e (k
g/s)
5.5 6 6.5 7 7.5 8 8.5 90.0E+00
5.0E-08
1.0E-07
1.5E-07
2.0E-07
2.5E-07
3.0E-07
Control Volume Height = 1.5 mm
3MP
3MP Theory
Hexane
Hexane Theory
Methanol
Methanol Theory
Control Volume Radius (mm)Di
ffusi
on R
ate
(kg/
s)
Traditional Theory vs. Real Hexane Data
-25 -20
-15
-10
-5
0
5
10
15
20
25 Radial Position, r [mm]
Elev
atio
n, z
[mm
]
0
5
10
15
20
25MeasuredComputed: Diffusion-Only
Summary• Vapor concentration data measured for methanol, hexane, and 3-methylpentane
• Data modeled by Gridfit
• Gridfit model used to compute gradients, calculate diffusion rates
• Diffusion rates and theory compared
• Evidence of convection found
Acknowledgments• Petroleum Research Fund• Dr. Peter Kelly-Zion• Dr. Chris Pursell• Dr. Hoa Nguyen• Chemistry Department, Trinity University• Engineering Department, Trinity University• Mathematics Department, Trinity University