| Summary: | 碩士 === 國防大學中正理工學院 === 兵器系統工程研究所 === 89 === The study of micro-channel flow is partly in response to the need for thermal control in the operation of MEMS in which the range of gas flow is from slip flow to transition regime. It will lead to incorrect results if we consider gas flow in micro-channel as continuum phenomena. In this paper, molecular approach DSMC has been used to study the flow and heat transfer characteristic of rarefied gas in micro-channel.
In one-dimensional simulation, a constant acceleration body force is applied to the system and the flow is restricted in laminar and subsonic state. The simulation results show that the discrepancies of hydrodynamic prediction are widening as indicated from velocity and temperature profiles when the flow in continuum regime transfers to slip flow regime, then low transition regime by increasing Knudsen number（Kn）. The data predicted by VHS model differ quantitatively from HS model, but it exists qualitative consistency between them. The macroscopic flow phenomena could be related to and described by the microscopic molecular motion based on simulation results.
Pressure-driven flows in micro-channel are simulated by varying inlet/exit pressure for a range of slip to transition regime flows. Both ambient and hot wall temperature cases are investigated. The simulation results of the former case show that the temperature in the flow field is lower than that of the channel wall. It is opposite to one-dimensional flow because of the difference of driving force. It is found that pressure distribution along the channel and streamwise velocity distribution in the transverse direction become more linear and flatter respectively with the increase of the Kn. In addition, the slip velocity increases along the streamwise direction.
In hot surface case, the heat flux through the channel wall is more pronounced than in the cold surface case. The flow properties such as temperature, density and pressure are strongly dependent on Kn and heat transfer. The effect of heat transfer from hot wall increases the rarefaction of the flow field and the inlet influence at the same boundary condition. Additionally, the pressure ratio in the flow field is higher than that without heat transfer.
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