Local Natural Convection Mass Transfer Measurements

Apparatus and experimental technique for measurements of local natural convection mass transfer on vertical and upward-facing inclined surfaces are described, and corresponding results are presented and discussed. The experiments were performed using the electrochemical technique, with Cu++ as the transferred ions and sulfuric acid as the supporting electrolyte. The objective of the research was to obtain highly local information. Two types of mass transfer probes were employed, the smaller of which were about 1/4 mm in spanwise width, with a probe-to-probe spacing of 1/20 mm. These miniature probes were used in the measurement of spanwise mass transfer variations encountered in the laminar-turbulent transition regime on inclined surfaces. Local laminar mass transfer results and instability Rayleigh numbers for vertical and inclined plates were measured by means of a set of small circular probes. All data were collected for limiting current operation, and the requisite concentration levels of CU+ + ions were examined and documented. In addition, the influence of cathode-to-anode orientation was investigated, as were the edge effects associated with the lateral edges of the test surface.