ISO A. The heat flow from the cell to the bath is determined from the temperature difference, Tc - T b and the heat transfer coefficient, determined by periodically calibrating the cell with an internal heater in the cell, by Newton's law of cooling. In this type of cell, TC varies and increases as the power output of the cell increases.
ISO B. The cell is maintained at a constant temperature by varying the power to the heater (heat substitution method). The cell is first brought to a given steady state temperature, Tc by the heater operating at a given power, Ph. The electrolysis cell is then turned on and the heater power decreased to a level, Phc, to maintain the cell temperature at Tc. The power generated by the electrolysis is calculated as Pc = Ph - P hc.