Upper and lower bounds for the heat flux in a gas between parallel plates

Waldmann's result for heat transfer through a monatomic gas between parallel plates is the starting point for the derivation of upper and lower bounds for the heat flux as a function of Knudsen number. In order to obtain numerical results, one transport-relaxation eigenfunction and its eigenvalue are determined approximately, and a simple model for the interfacial kernel of the kinetic boundary condition for the distribution function is used. (orig.)