Heat Flow Measurements in Gas Mixtures of Air with Undecane or Water Vapor Exhibiting Phase Transitions

Heat flows characterizing free thermoconcentration convection of air–gas mixtures with undecane or water vapor, exhibiting first-order phase transitions, were measured. In the case of undecane, the Nu(Ra) dependence closely matches that of dry air. It is shown that experimental data for humid air require supplementary numerical processing, accounting for intensive and complex diffusive mass transfer. The role of thermodiffusion and Stefan flow in humid air is discussed.