Effect of concentration gradient on composition of sampled gas. II. Experimental verification

The sampling probe theory for a rectangular probe given in report I of this series was experimentally verified. Sampling was made in a counter flow of hydrogen and nitrogen by rectangular probes with various widths, which simulated the two-dimensional probe. Different concentrations were obtained by the respective probes at the same sampling position. They were corrected by the theoretical diffusional-flux recovery factor into one value which may be regarded as a true concentration. The diffusional-flux recovery factors estimated experimentally in the counter flows with various velocities agreed well with the theoretical values. The concentration disturbance in front of the probe inlet caused by the probe insertion was directly measured by a fine needle probe, and the results agreed well with the profile determined from the numerical solutions of the previous report. These experimental results seem to support the theoretical analysis for a cylindrical probe as well as for the rectangular probe.