A time-dependent mathematical model of a parallel-plate reactor was developed to study the electrochemical fluorination of organic compounds dissolved in anhydrous hydrogen fluoride. The model incorporates two-phase flow with differential material, energy and pressure balances. Dynamic results are presented that show the effect of disturbances to the whole reactor or one of the cells of the multicell reactor. The effect of disturbances in the cell current and inlet electrolyte flow rate on the cell voltage, molar flow rates, and current efficiency is studied. Also, the effect of a blockage in inlet flow to one cell in the cell pack is studied for cases when heat transfer is either present and absent between the adjoining cells.