TRANSPORT OF NOBLE GASES IN GRAPHITES. Progress Report for the Period January 31, 1961 to January 31, 1962
A model was derived for the diffusion of gases in porous media in the absence of temperature and pressure gradients, in which portions of the medium are visualized as a collection of uniformly distributed dust'' particles (giant molecules) which are constrained to be stationary. Thus, it was possible to derive all the desired results from rigorous diffusion equations for multi- component mixtures. The results apply over the entire pressure range from the Knudsen region to the normal diffusion region. This model permits a satisfactory derivation of the fact that, at all pressures, the flux ratio of two counter- diffusion gases is (m/sub 2/mi/sub 1/)/sup 1/2/ in porous media under steady state and uniformpressure conditions. The effect of non-zero pressure gradients on the diffusion equations is to introduce into the fundamental kinetic theory equations both a pressure diffusion term and an external force term. There is a considerable cancellation of terms, and the final diffusion equation has the same form as in the uniform pressure case. No additional parameters beyond those necessary to define a diffusing system at uniform pressure are thus required to compute the diffusion rates when pressure gradients are present. A complete solution requires also a forced flow equation giving J (the net flux) as a function of the pressure gradient. A forced flow equation is derived on the basis of the dusty-gas model, but one parameter must be made disposable in order to compensate for the fact that the model permits only a diffusive mechanism for flow, never a viscous mechanism. A series of experiments with helium and argon in graphite is discussed as well as the possibility of extending the model to include the effects of temperature gradients. (auth)
- Research Organization:
- Oak Ridge National Lab., Tenn.
- DOE Contract Number:
- W-7405-ENG-26
- NSA Number:
- NSA-16-009209
- OSTI ID:
- 4807661
- Report Number(s):
- ORNL-TM-135
- Country of Publication:
- United States
- Language:
- English
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