The effects of Reynolds number, Schmidt number, and shape factor of the electrodialysis cell on the Nusselt number in ion exchange membrane electrodialysis have been investigated. An empirical correlation is obtained at limiting current density for solutions of five electrolytes, CH//3COONa, NaCl, CuSO//4, NiSO//4, and H//2SO//4, in a planar electrodialysis channel. The correlation is in good agreement with the theoretical performance equation.