Numerical Calculation of Concentration Profiles within Thermal Diffusion Column with Continuous Feed and Draw-Offs

Abstract

Axisymmetric concentration profiles of an isotope separating thermal diffusion column with continuous feed and draw-offs were calculated by solving the convectiondiffusion equation using Newton iterative method, where the flow variables are specified from the input data.Computations were performed for 36 Ar and 40 Argas mixture within the cylindrical column having inner hot radius of 0.15 mm and an outer cold radius of 7.5 mm, between which the temperature differs by 515 K.The rate of feed F, supplied into the middle-height point of the column, was varied from 2. 72 x 10-4 g/s (1 0 em 3 I min at 25C) to 5.45 x 10-3 gfs (200 cm 3 /min), while the cut (J, or the ratio of the upper drawing-off to feeding rates, from 0.1 to 0. 9.The pattern of concentration profile depends largely on the value of the total transport (that is, (J Fin the upper section and -(1-(J) F in the lower section), and the two different patterns are linked at the feed point.The effect of changes in hot wire temperature (723-973 K, temperature differences: .dT=435 ~ 685 K) and in cold wall radius (r, = 7.5 and 5 mm) were also analyzed to find the value ofF/ (L1T r~) less than -0.02/(sK em) is necessary for effective separation.