JOULE HEATING IN ELECTROCHEMICAL-CELLS EXPERIENCING NATURAL-CONVECTION AND ELECTROLYTE STRATIFICATION

The Joule heating is studied theoretically in a simple electrochemical cell formed by two vertical metallic electrodes and two electrochemic ally inert horizontal boundaries. The cell contains an aqueous solutio n of a metal salt as the electrolyte. The voltage across the cell is a ssumed to be specified. A convective electrolyte flow emerges in the c ell in the course of electrolysis. A steady-state mode of the cell ope ration, which is characterized by large values of the Rayleigh number and the applied voltage, is considered. The heat contribution in the n atural convection is shown to be negligible, compared with the convect ion that is due to changes in the solution density caused by variation s of its composition. In the steady-state mode, the solution becomes s tratified, which affects significantly the electrolyte flow. The elect ric current distribution in the vertical direction is shown to be nonu niform, which results in a nonuniform heat generation and a nonuniform temperature distribution. The procedure developed can be useful (afte r slight modifications) for studying heat effects in lead-acid batteri es intended for electric engines.