Heterogeneous activation of rarefied hydrogen in thin tubes

•Rarefied hydrogen flow through a cylindrical channel is considered.•Heterogeneous reactions of dissociation-recombination on the surface are studied.•The direct simulation Monte Carlo method is used as a numerical technique.•Effect of conditions on dissociation degree of coming out hydrogen is analyzed.•Method of evaluating the dissociation and recombination coefficients is proposed.

The direct simulation Monte Carlo method was used to study the rarefied gas flow through a cylindrical channel, taking into account heterogeneous reactions of dissociation-recombination on the surface. The main emphasis was placed on the study of the influence of heterogeneous processes on the degree of dissociation of the flow, coming out of the channel. The study was conducted for different relations of the channel length to its radius, coefficients of dissociation and recombination, and in a wide range of gas rarefaction degrees: from free molecular to transitional regimes. The obtained results may be useful for optimization of gas-dynamic sources ​of activated gas, based on thin tubes.