We present mass flow measurements and pressure distributions in near unity aspect ratio microchannels using Deep Reactive Ion Etching (RIE). Almost all of the previous papers have dealt with only wide channels for gas flow measurements. We also adopt Spin-On-Glass (SOG) to bond Pyrex glass to silicon. Using the first order slip flow formula and experimental data, we extracted the tangential momentum accommodation coefficient (TMAC) of 0.425 for the case of SOG and Si microchannels and air, and the effective diameter of 57.67μm. Increased mass flow from the incompressible flow case is mostly due to compressibility rather than rarefaction, which is expected from the fact that the Knudsen number is 0.00115, the borderline of slip flows. The deviations from the linear incompressible pressure distributions get larger with increasing inlet pressures, and the dimensionless streamwise locations of maximum deviations are between 0.5 and 0.6, which is slightly downstream from the middle of the channels. It is notable that these experimental data are much closer to simulation results than the previous experiments in microchannels. The inlet pressure drops are almost linear with respect to pressure ratio of inlet to outlet. This type of near unity aspect ratio microchannel is more effective for heat exchangers than previous thin, wide channels.

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