Heat and mass transfer performance of ferricyanide/ferrocyanide thermocell and optimization analysis

Thermocell, as a device of thermoelectric conversion, can directly convert waste heat into electricity without moving parts and gas emissions. The overall numerical thermocell model is an effective tool used to study different processes and phenomena of heat and mass transfer. In this study, the mathematical model of Fe(CN)63−/4- thermocell was established and numerically analyzed. The influence of cell's size, temperature difference, electrolyte concentration, and electrode structure on the output power and efficiency of thermocell were studied under the multiple physical fields of temperature, velocity, concentration, and electrochemical reaction. The results revealed that higher cell's height, shorter cell's length, and higher concentrations tend to maximize electrical output power. At the cell's height of 10 mm, cell's length of 2 mm, the temperatures of the hot side and cold side of 310.55 K and 290.55 K respectively, and initial concentrations of ferrocyanide and ferricyanide of 400 moL/m³, yielded the maximum value of electrical output power of 6.75 μW. This research demonstrated that improving the performance of the thermocell depended not only on electrochemistry and materials, but also on design optimization. Combining the influence of temperature difference and electrolyte concentration, the optimization strategy including the size, temperature, concentration, and structure of thermocell was further proposed. The established thermocell model and the proposed optimization strategy can provide guidance for the designing of thermocells having higher output and conversion efficiency in the future.