Pressure drop measurements in a microchannel

Recent developments in micro-energy and micro-chemical systems have produce d a need for greater understanding of flow in small channels. Several recen t studies of friction factors and transition Reynolds numbers in rectangula r microchannels have produced results that differ from classical theory. In this work, friction factors and laminar flow friction constants were deter mined for water flowing in high aspect ratio channels with depths ranging f rom 128 to 521 mu m. Reynolds numbers were between 60 and 3,450 Pressure dr ops were measured within the channel itself to exclude entrance and exit lo sses. Transitions to turbulence were observed with flow visualization. Unce rtainties in measured variables were quantified and propagated into the est imated friction constants. Friction factors were also determined in a 1,050 -mu m-deep channel that served ns a control After considering experimental uncertainties and systematic errors, significant differences remained betwe en the results and classical theory.