Dynamics of Vapor-Air Mixtures

Although it is generally recognized that density differences affect the vertical movement of gases, the downward flow of heavier-than-air mixtures has received little experimental attention. On theoretical grounds, a very small density increase can produce downward flow. Experimentally, a density difference of 0.6% was sufficient to induce vertical gas flow in a pipe. From a series of observations it was found that the relationship of density to flow rate can be characterized, and that in unrestricted systems the maximum concentration of heavy vapor is far less than that predicted from vapor pressure data. This maximum is related not only to vapor pressure, evaporation rate, temperature, etc., but also to the fact of downflow and air induction associated with it.