A flow method for measuring transport properties at flame temperatures

Abstract

A dynamic diffusion experiment, in which the spread of a tracer material in a laminar stream is followed by appropriate sampling and analytical means, should be well suited for use at high temperatures. Compared with static methods of the Loschmidt type, which have been used at high temperatures in one investigation ( l ) , the dynamic method permits a wider choice of construction materials and shortens significantly the time period required for an experiment.The advantages of the dynamic method were pointed out by Walker and Westenberg ( 2 ) who used the technique for measurements of binary diffusion coefficients up to 1,150"K. These workers preheated the main gas stream to the temperature of the experiment and then made the stream laminar by passing it through a series of screens. They admitted tracer gas through a capillary tube pointed in the direction of flow, sampled downstream with a similar capillary, and analyzed their samples by thermal conductivity methods.Two significant modifications of this scheme are made in the work described here. The hot, laminar gas stream is composed of the combustion products from a thin, flat flame which bums at the base of the apparatus. This permits investigations at higher temperatures because materials problems involved in preheating the gas and making the flow laminar are avoided. The present method also uses radioactive tracer techniques for analysis. This makes possible the measurement of self-diffusion coefficients as well as binary diffusion coefficients and permits extensive cross checking of diffusion phenomena in multicomponent gas mixtures. A brief description of the apparatus, together with selfdiffusion data for carbon dioxide at 1,180" to 1,680"K. has been given previously ( 3 ) . The purpose of this paper is to present a fuller discussion of the construction features of the apparatus and of recent modifications of the apparatus and the method. Self-diffusion and binary diffusion data for the carbon dioxide-methane system at I TemperaturesGeorge Ember is with the American Oil Company, Whiting, Iudiana.

Diffusivities in System: Carbon Dioxide-Nitrogen-Argon

“…The experimental apparatus and procedure and the methods of data analysis have been described in detail (9). A brief summary of these and description of one improvement that has been made for the current measurements are provided here.…”