A kinetic model for gas adsorption-desorption at solid surfaces under non-equilibrium conditions

One-dimensional flows of a polyatomic gas in the presence of an adsorbing-desorbing surface kept at constant and uniform temperature are simulated by numerically solving the Boltzmann kinetic equation by the Direct Simulation Monte Carlo (DSMC) method. It is considered the flow of gas between two planar and infinite surfaces, where only one surface is able to adsorb and desorb molecules, while the other one is impermeable. Borgnakke-Larsen model is used to describe inelastic collisions dynamics. for a gas of rigid rotators. The adsorption and desorption phenomena are simulated by a kinetic model which includes the classical Langmuir description as a limit case and leads to an additional equation for the time evolution of the surface coverage to be solved along with the gas dynamics. Furthermore, the analytical solution is developed for free molecular flow regime. The comparison between the analytical solution and the results obtained by the numerical solution for this regime shows a very good agreement.