Flow Characteristics in a Trapezoidal Silicon Microchannel

In this paper, global pressure drop and velocity field were experimentally investigated for water flow in trapezoid 30mm long microchannels with a hydraulic diameter of 238μm. A micro-PIV system was used to obtain the velocity profiles at different locations of the microchannel. For Re > 500, Δp/L-Re relationship deviates from the linear relationship and the deviation depends on the Re. The experimental results of the velocity field show that the deviation is due to the entrance effect in microchannel, and the entrance length in our experiments can be predicted by Le/D_h = (0.07 ∼ 0.09)Re. Velocity profiles and root mean square values of the fluctuating centerline velocity obtained by micro-PIV indicate that the transition from laminar flow to turbulent flow has occurred between 1500 and 1800. This result is consistent with the global measurements of pressure drop.