Chemistry Reference
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300.0
295.0
290.0
285.0
280.0
275.0
270.0
265.0
260.0
255.0
250.0
0
10
20
30
40
50
60
70
X position (nm)
Figure 4.13
Temperature gradient for methane between two parallel plates at
x
=
0,
maintained at 300 K, and at
x
1 nm, maintained at 250 K. The black line shows the
average temperature profile shown with a 0.5 % variation.
=
7
.
of the method. There is almost no experimental data available for meso scale sys-
tems and computational restrictions limit comparisons on the continuum scales,
so tests are performed at high-end molecular scales where information on simu-
lations is readily available. This also allows the testing of the molecular model
separately from the approximating (least squares) components.
The molecular dynamics model was tested against the molecular simulations
performed by Sokhan
et al.
[60], whose simulations were performed using a
model based on the DL POLY [89] package. The system considers fully devel-
oped Poiseuille flow of methane through a graphite slit pore.
The system is simplified to methane molecules flowing between two parallel
plates of graphite, which contain the molecules in the
y
direction and periodic
boundary conditions in the
x
and
z
directions. The system dimensions are shown
in Figure 4.14, with the graphite plates being separated by 7.1 nm; the lengths
of the simulating cell in the
x
and
z
directions are 7.715 nm and 8.368 nm re-
spectively. Into this volume was put 5104 methane molecules, corresponding to a
reduced density of
ρ
=
0
.
61 and interacting via a Lennard-Jones potential with
a collision radius
σ
=
0
.
381 nm and a well depth
/
k
b
=
148
.
1K.
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