Axial static pressure measurements of water flow in a rectangular microchannel

Abstract

An experimental investigation of water flow through an aluminum rectangular microchannel with a hydraulic diameter of 169 μm was conducted over a Reynolds number (based upon mean velocity and hydraulic diameter) range from 230 to 4,740. Pressure measurements were simultaneously acquired at eight different axial locations within the channel along with pressure measurements in the inlet and outlet ports. The 27 μm pressure taps were more densely packed near the channel entrance in order to study the developing flow region. The average Poiseuille number for laminar flows was 86.4, which is in excellent agreement with the theoretical value of 86.9. The average critical Reynolds number was found to be 2,370. The limited turbulent friction factor data were in good agreement with the Haaland equation. The inlet to the channel was not well rounded and pressure distributions near the channel entrance show a region of pressure recovery. Entrance length and some minor loss coefficient data were not in agreement with theory, but the cause of these deviations were primarily a function of the inlet geometry and pressure recovery in the microchannel rather than a microscale effect.