Differences between revisions 7 and 8
 ⇤ ← Revision 7 as of 2020-05-08 05:42:51 → Size: 1599 Editor: KeithLofstrom Comment: ← Revision 8 as of 2020-05-08 05:43:32 → ⇥ Size: 1610 Editor: KeithLofstrom Comment: Deletions are marked like this. Additions are marked like this. Line 20: Line 20: At 25C and 100KPa: At 25C and 100KPa  (or STP?):

Mean Free Path

From CRC100:

 l mean free path m d hard sphere diameter m P pressure Pa| \eta viscosity μPa s m molecular mass kg M molar mass g/mole \tau mean time between collisions s \overline v mean velocity m/s

l = { \Large { { k T } \over { \pi \sqrt{ 2 } P d^2 } } } ~ = ~ { \Large { 9.27e-27 \over { d^2 } } }

d^2 = 2.669E-20 \sqrt( M T ) / \eta ~~~ m² ... compute diameter from viscosity

\overline{ v } = { \Large \left( { 8 k T } \over { \pi m } \right) } = 145.5\sqrt(T/M) ~~~ m/s

At 25C and 100KPa (or STP?):

 gas d l \overline v \tau \eta Å nm m/s ps μPa s NH₃ 4.32 49.7 609 82 10.2 Ar 3.58 72.2 397 182 22.7 CO₂ 4.53 45.1 379 119 14.9 He 2.15 200 1256 159 19.9 H₂ 2.71 126 1769 71 8.9 Kr 4.08 55.8 274 203 25.4 Ne 2.54 143 559 256 32.0 N₂ 3.70 67.6 475 142 17.8 O₂ 3.55 73.6 444 166 20.7 Xe 4.78 4.05 219 185 23.1 H₂O 9.9 CO 17.8 CH₄ 11.1

also CRC Handbook of Thermophysics p407

MeanFreePath (last edited 2020-05-08 05:43:32 by KeithLofstrom)