A kinetic theory analysis of evaporation and condensation of a diatomic gas

The evaporation and condensation problem of diatomic gas was studied based on the BGK–Morse kinetic model equation. The results showed that (1) the macroscopic jump coefficients were insensitive to the variation in the relaxation time of internal energy, (2) the pressure jump caused by evaporation (condensation) or by heat transfer was almost the same as the value of a monatomic gas, and (3) the temperature jumps of a diatomic gas were smaller than those of a monatomic gas in accordance with the quantities of specific heats. Approximate expressions of macroscopic jump coefficients of a diatomic gas for arbitrary values of the internal degrees of freedom and those of accommodation coefficients of mass, translational energy, and internal energy are obtained using the jump coefficients of a monatomic gas.