GAS FLOWS IN A MICROTUBE/MICROCHANNEL

For the gas flow in a long microtube, the general numerical methods, such as DSMC, encounter difficulties due to the enormous length diameter ratio. A simplified system of control equations is derived for slip flow in a long microtube, and then an iterative method is used to solve the equations combined with slip boundary conditions on the solid wall to give the distribution of flow velocity, density, and thus the mass flow rate. The experimental study shows that: The mass flow rate obtained by the simplified computation is rational at Knudsen numbers 3×10 -3 ～7×10 -3 ; The compressibility of microscale flow is obvious even though the Mach number is very small. The DSMC study of gas flow in a microchannel reveals that the rarefied gas effect enhances, and the difference between the slip flow solution and the result of DSMC becomes larger as the Knudsen number is increased. Therefore the slip flow solution is not accurate for microscale flow at such Knudsen numbers.