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The TECMDL computer code has become a prevalent and useful tool for analyzing thermionic converters and power systems. This paper describes a brief derivation of the physical model used as the basis of this code and presents comparisons of calculated with experimental converter performance data. A brief description of the code's practical use is presented, along with possible areas for future improvement.

A physical-analytical model has been formulated for computing the emission and vaporization properties of a surface immersed in a multi-species vapor. The evaporation and condensation processes are assumed to be identical to those for an equilibrium adsorbed phase in equilibrium with its vapor, permitting statistical mechanical computation of the sticking coefficient for the practical non-equilibrium condensation condition. Two classes of adsorption sites are defined corresponding to superficial and interstitial coadsorption. The work function is computed by a self-consistent summation over the dipole moments of the various coadsorbed species in their mutual electric field. The model adequately describes observed emission and evaporation from tungsten surfaces immersed in pure cesium vapor and in pure oxygen vapor.