Knudsen gas

A Knudsen gas is a gas in a state of such low density that the average distance travelled by the gas molecules between collisions (mean free path) is greater than the diameter of the receptacle that contains it.[1] If the mean free path is much greater than the diameter, the flow regime is dominated by collisions between the gas molecules and the walls of the receptacle, rather than intermolecular collisions with each other.[2] It is named after Martin Knudsen.

An example of a Knudsen gas. There are more collisions between the gas molecules and the receptacle walls (shown in red) compared to collisions between gas molecules (shown in blue).
  1. ^ Pardington, J.R. (1949). An advanced treatise on physical chemistry. Vol. 1, Fundamental principles. The Properties of gases. London: Longmans, Green & Co. p. 927.
  2. ^ Lebon, G. (2008). Understanding non-equilibrium thermodynamics : foundations, applications, frontiers. D. Jou, J. Casas-Vázquez. Berlin: Springer. p. 192. ISBN 978-3-540-74252-4. OCLC 233973416.