Gas flow and heat transfer characteristics in the entrance region of microtubes

First order slip velocity and jump temperature boundary conditions are employed to determine the developing flow and heat transfer in the entrance region of a microtube. The influences of the Knudsen number, the momentum accommodation coefficient and the thermal accommodation coefficient are investigated numerically. The results show that the flow developing length increases with the Knudsen number while decreases with the momentum accommodation coefficient; the thermal developing length increases with the Knudsen number while decreases with the momentum accommodation coefficient and the thermal accommodation coefficient; the Nusselt number decreases with the increase in Knudsen number and the thermal accommodation coefficient while increases with the decrease in the momentum accommodation coefficient.