Energy and exergy analysis of an irreversible thermionic generator

A new thermodynamic model of an irreversible thermionic generator (TIG) is proposed in which internal as well as external heat losses of the system have been considered. The operating temperatures of cathode and anode have been determined by writing energy balance equations for both electrodes. The expressions for power output, irreversibility, entropy generation, energy and exergy efficiency have been derived analytically. The effect of anode work function and output voltage on the net current density, power output, energy and exergy efficiency has been discussed. For the given operating conditions, the maximum power output, energy and exergy efficiency have been calculated numerically and the optimally operating range of several important parameters has been determined. The criteria for optimization of both design and performance, which may be helpful for choice of cathode and anode material, has been obtained. The results obtained in this study will be helpful in the designing of a practical irreversible thermionic generator and it will give a better understanding of thermodynamic modeling, irreversibilities and entropy generation in the thermionic generator.