The efficiency of a method of machineless gasdynamic energy stratification, based on heat transfer between sub- and supersonic flows separated by a thin wall, is studied numerically. A model flow consisting of two (sub- and supersonic) steady-state laminar boundary layers separated by a thin heat conducting plate is considered. In the first part, pure-gas flows with different Mach and Prandtl numbers are investigated. In the second part, the effect of an admixture of small droplets evaporating inside the supersonic boundary layer on the efficiency of the considered energy stratification scheme is examined. The case of a thermally insulated wall between the boundary layers is also studied. It is shown that the presence of even a very low (of the order of a percent) mass concentration of evaporating liquid droplets in the supersonic stream may result in a significant increase in the difference between the average stagnation temperatures of the gases passed through the sub- and the supersonic boundary layer on both a thermally insulated and a heat-conducting plate, and hence may be a promising way to enhance the energy separation efficiency. (C) 2016 Elsevier Ltd. All rights reserved.