This paper presents an experimental investigation of laminar gas flow through microchannels. The independent variables: relative surface roughness, Knudsen number and Mach number were systematically varied to determine their influence on the friction factor. The microchannels were etched into silicon wafers, capped with glass, and have hydraulic diameters between 5 and 96 μm. The pressure was measured at seven locations along the channel length to determine local values of Knudsen number, Mach number and friction factor. All measurements were made in the laminar flow regime with Reynolds numbers ranging from 0.1 to 1000. The results show close agreement for the friction factor in the limiting case of low Ma and low Kn with the incompressible continuum flow theory. The effect of compressibility is observed to have a mild (8 percent) increase in the friction factor as the Mach number approaches 0.35. A 50 percent decrease in the friction factor was seen as the Knudsen number was increased to 0.15. Finally, the influence of surface roughness on the friction factor was shown to be insignificant for both continuum and slip flow regimes.

Issue Section:
Micro/Nanoscale Heat Transfer
Keywords:
channel flow, laminar flow, surface roughness, Knudsen flow, Mach number, friction, etching, compressibility, slip flow, Channel Flow, Experimental, Heat Transfer, Microscale, Rarefied, Roughness
Topics:
Flow (Dynamics), Friction, Microchannels, Surface roughness, Pressure, Gas flow, Compressibility
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