The Free Expansion of Dry and Moist Air

Abstract

If a gas is permitted to expand freely from a vessel of constant volume, the gas remaining in the vessel is generally considered to undergo reversible adiabatic expansion. For such a case, the theoretical backgrounds are developed from the points of view of thermodynamics and gas dynamics. Experiments are reported in which it is shown that, for expansions occurring over short time intervals, the temperature changes are essentially those predicted for reversible adiabatics. Some speculations are offered as to the mechanisms obtaining in the slower expansions.