THEORETICAL AND EXPERIMENTAL STUDIES OF FREE-CONVECTION AND STRATIFICATION OF ELECTROLYTE IN A LEAD-ACID CELL DURING RECHARGE

Free convection and stratification of the electrolyte in a lead-acid cell with porous electrodes and during recharge were studied theoretically and experimentally. The concentration field was measured by means of Holographic Laser Interferometry (HLI) and the velocity field by means of Laser Doppler Velocimetry (LDV). A two-dimensional mathematical model was also developed for mass transfer and electrolyte motion during the process. It was assumed for simplicity that the electric current density and porosities of the electrodes were constant and uniformly distributed in the electrodes. The results from the experiments were compared with numerical results obtained from the mathematical model. The agreement was found to be good. A simplified mathematical model, as an alternative to the full numerical problem, was also developed. The results of the simplified model proposed here proved to be in good agreement with the results from the full numerical solution, albeit for sufficiently large times.