Abstract
Application of a dynamic or unsteadyβstate technique to the problem of radial mixing in a tube is described. Measurement of the amplitude attenuation suffered by a sinusoidally modulated gas composition wave as it flows within an open (unpacked) tube makes possible the direct determination of an βequivalent gas film thicknessβ from which a mass transfer film coefficient may be readily calculated.
A brief summary of the method employed for obtaining the necessary mathematical relationships is presented, along with descriptions of the techniques developed for measurement of small amplitude differences at wave frequencies as high as 10 cycles /sec.
Experimentally, conditions were varied to include a range of Schmidt number from 0.18 to 1.24 and of Reynolds number from 4,000 to 50,000. The results of this work appear to fall nearly in line with the semitheoretical equation of Martinelli as written for mass transfer. Generally speaking, a was found to be an increasing function of N~Sc~, varying from about 0.5 to a maximum of 0.77; Ξ², in turn, was found to increase with N~Re~ from 0.3 to 0.5.
A suggestion for extending the method to measurement of eddy diffusivities in the axial direction is included.