Diffusion-thermo effects in stagnation-point flow of air with injection of gases of various molecular weights into the boundary layer

This paper is conceined with the effect of diffusion thermo on the heat transfer, mass transfer, and flow in a boundary layer into which various foreign gases are injected Air is the mainstream gas Particular consideration is given to the question of how the magnitude of the diffusion-thermo effect is related to the molecular weight of the injected gas Correspondingly, the analysis includes injection of hydrogen, helium, argon, carbon dioxide, and xenon; the selection of these was also influenced by the availability of transport and thermodynamic properties The study is carried out for plane and axisymmetiic stagnation flow in forced convection and for plane stagnation flow in free convection One effect of diffusion thermo is to create an adiabatic wall temperature T_aw different from the stream temperature It is found that the diffusion-thermo effect is much stronger for injection of H₂ and He (molecular weight less than air) than for injection of A, CO₂, and Xe (molecular weight greater than air) A heat-transfer coefficient denned with (T_w − T_aw) as thermal driving force is not strongly affected by diffusion thermo Additionally, for the case of the highlycooled wall, the heat-transfer rate is itself not too much affected by diffusion thermo.