Direct comparison between a variety of microchannels part 2: Experimental description and flow friction measurement

Part 1 of this paper (Eason et al 2004) investigates the manufacturing of a variety of microchannels, produced by wet and dry etching in silicon, as well as precision mechanical sawing in silicon and thermoset plastic. This paper describes the experimental equipment and methods used to measure the pressure flow characteristics of the manufactured channels. A custom designed test system has been built in order to test each sample using the same inlet and outlet manifolds, pressure tappings, pumping system and instrumentation. The pressure drop across each set of channels was measured using an inductive pressure transducer. The mass flow rate through the system is measured by weighing the flow from the system in a given time. The measured pressure flow behaviour was compared with theoretical values as calculated from macro scale theory. Channel dimensions used for this calculation are as measured in part 1 of this paper. Error analysis was then carried out in order to determine the overall accuracy of the experimental work and determine whether any deviation from theoretical values is of experimental significance. This step is essential in any attempt 10 determine whether microchannel flows are indeed different to macro scale flows in a fundamental way. The deep reactive ion etched (DRIE) channels show the most significant lack of correlation with theoretical predictions. Compensation must be introduced to deal with the difference in cross section between the perfectly rectangular channels used for the theoretical prediction and the actual cross section of the channels.