Slow Flow of a Dissociated Gas about a Catalytic Probe

A solution to the problem of the flow at low Reynolds number of a dissociated gas about a catalytic probe has been obtained using the method of inner and outer expansions. The solution gives the atom concentration distribution about the probe as a function of the Reynolds number based on diffusion and the parameter K = kw′a/D, where kw′ is the effective speed of the surface reaction, D is the diffusion coefficient, and a the radius of the probe. It is shown that, from a measurement of the heat transfer to the probe and an independent measurement of the free stream atom concentration, one can establish the catalytic efficiency of the surface when K « 1 and the diffusion coefficient when K » 1. Conversely, knowing either the diffusion coefficient or the catalytic efficiency, the probe may be used to determine atom concentrations. The results of the theory are used to establish experimental conditions in a glow discharge facility under which the sought data may be obtained. Plots of valid operating regimes of this facility are presented as examples.