Dispersion of matter in transitional flow through straight tubes

Abstract
Dispersion of matter in two tubes of diameter 0.684 and 2.77 cm and length 24 m (80 ft) was studied in three gaseous systems, namely, N 2 :C 2 H 4 , N 2 :A, N 2 :He. The Reynolds number variation was 2 x 10 2 to 10 4 . The results were compared with the theory due to Sir Geoffrey Taylor which was up dated by inclusion of an accurate velocity profile. Particular attention was paid to the transition flow regime in which intermittency parameters were measured. It is shown that the theory is adequate beyond the transition regime, but the interpretation of results cannot be quantitatively satisfactory because of lack of precise data on turbulent transfer of matter. Dispersion in the transition regime is influenced by turbulent slugs but experimental results are surprisingly close to predictions from the turbulent flow theory. The position of the maximum of the dispersion parameter was measured and its dependence on the length to diameter ratio of the tubes, and the Schmidt and Reynolds numbers of the system is explained. The reasons for asymmetric response curves for transitional flow lies in the retention of tracer in the recirculating regions set up between adjacent laminar regions and turbulent slugs.

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