Variable-conductance wall based on the Knudsen conduction regime

We describe the operation of a vessel with variable-conductance walls, based on the superposition of heat transfer by radiation and conduction through a rarefied saturated-vapor, in transition between the Knudsen and the continuum behavior. The rarefied vapor fills a narrow gap between two thin walls. We derive an analytical correlation to estimate the heat flux between the two thin walls and through the narrow gap filled by rarefied saturated-vapor. We discuss the heat transfer characteristics of such a container for some cases of technological interest. We present a set of design criteria.