Mass Transfer at Longitudinally Vibrating Vertical Electrodes

Experimental measurements of limiting currents were carried out to determine the increase in mass transfer rates as a result of longitudinal vibrations applied to vertical flat-plate electrodes. Three different lengths of the electrode active areas (1.27, 2.54 5.08 cm), three different vibration amplitudes (0.0572, 0.114, and 0.229 cm), and several different vibration frequencies (ranging from 13 to 36 Hz) were used in the experiments. The current is a sum of a small a-c current and a large d-c current. The a-c current profile, which has a phase lag of 90/sup 0/, depends on the location of the electrode active area and the vibration parameters. With the experimental conditions used, the average mass-transfer coefficients are in the range of 2.8 - 14 x 10/sup -4/ cm/s, which represents an increase to 1.2 to 5 times the value for the average free-convective mass-transfer coefficient. A correlation similar to that derived from boundary-layer theory for forced convection over a flat plate is given for predicting the mass-transfer coefficient from the length of electrode active area and the vibration parameters.