ELECTRO-CHEMICAL MEASUREMENTS OF MASS-TRANSFER IN SEMI-CYLINDRICAL HOLLOWS

Measurements are described of the circumferential distribution of local Sherwood number in a semi-cylindrical hollow oriented transverse to the main flow in the base of a narrow rectangular channel. This geometry, among other reasons, is of interest because of its application to blood oxygenation equipment. The experimental arrangement was such that hydro-dynamically fully-developed laminar flow existed at entry to the hollow, and measurements covered a Reynolds number range of about 20-500 based on the hollow diameter and channel mean velocity. An electro-chemical technique, in which a redox couple comprised the electrolyte and thin nickel wires formed the test electrodes, was utilized. Current measurements, made under conditions of diffusion-controlled electrolytic reaction, led to the evaluation of the Sherwood number. The circumferential distribution of Sherwood number within the hollow as a function of the Reynolds number of flow and the hollow size are presented in graphical form. Sherwood number increased with both the Reynolds number and the hollow diameter, but it usually exhibited a minimum somewhere in the upstream quadrant of the hollow. The Sherwood number, averaged over the hollow circumference, was computed and yielded a correlation identical to the one in the absence of the hollow, except for a smaller value of the constant. The results were compared with a numerical calculation by Snuggs and Aggarwal of the Sherwood number distribution in the hollow and were found to be in excellent agreement. © 1979.