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VIII.—Theoretical Expressions for Relaxation Effects in the Thermal Conductivity of Gases as Measured in the Modified Co-axial Cylinder Apparatus of Callear and Robb

Published online by Cambridge University Press:  14 February 2012

P. G. Wright
P. G. Wright
Affiliation:
Department of Chemistry, Queen's College, Dundee.
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Synopsis

The apparent thermal conductivity of a polyatomic or isomerizing gas (as measured in a given apparatus) may decrease at low pressures for two distinct reasons. There may be accommodation effects at boundary surfaces, and there may be relaxation effects arising because molecules with excess energy do not yield it up fast enough to maintain local “chemical” equilibrium. If the apparatus is such that the temperature measured at points in the gas and not in the walls, relaxation effects may be observed directly, and accommodation effects are (in theabsence of relaxation effects) absent.

A detailed analysis is made of the apparent thermal conductivity measured in such an apparatus with cylindrical symmetry. Expressions are obtained in closed form. Numerical calculations show that, for a gas of relatively long relaxation time in an apparatus of reasonable dimensions, the apparent thermal conductivity would decrease appreciably at readily-attained pressures.

Type
Research Article
Information
Proceedings of the Royal Society of Edinburgh Section A: Mathematics , Volume 66 , Issue 2 , 1962 , pp. 81 - 92
Copyright
Copyright © Royal Society of Edinburgh 1962

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