Pressure drop measurements in a microchannel

Recent developments in micro-energy and micro-chemical systems have produced a need for greater understanding of flow in small channels. Several recent studies of friction factors and transition Reynolds numbers in rectangular microchannels have produced results that differ from classical theory. In this work, friction factors and laminar flow friction constants were determined for water flowing in high aspect ratio channels with depths ranging from 128 to 521 mu m. Reynolds numbers were between 60 and 3,450 Pressure drops were measured within the channel itself to exclude entrance and exit losses. Transitions to turbulence were observed with flow visualization. Uncertainties in measured variables were quantified and propagated into the estimated 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 between the results and classical theory.