An overview is given of research activities in the field of fluid components or systems built with microfabrication technologies. This review focuses on the fluidic behaviour of the various devices, such as valves, pumps and flow sensors as well as the possibilities and pitfalls related to the modelling of these devices using simple flow theory. Finally, a number of microfluidic systems are described and comments on future trends are given.
Micromachined silicon diaphragm valves are fabricated and flow characteristics are related with laminar and turbulent flow theory. Simultaneous measurements of flow, pressure and lift height are presented. Flow rates of 200 ml min-1 at 0.7 bar are demonstrated, making these valves suitable as pilot valves in various applications such as refrigeration and hydraulics.
This paper presents the application of optical measurement techniques in dense-gas flows in a heavygas channel to determine planar two-component (2C) velocity profiles and two-dimensional (2D) temperature profiles. The experimental approach is rather new in this area, and represents progress compared with the traditional techniques based on thermocouple measurements. The dense-gas flows are generated by the evaporation of liquid nitrogen. The optical measurement of both the velocity and density profiles is accomplished by the implementation of particle image velocimetry (PIV) and background-oriented schlieren (BOS) systems. Supplemental thermocouple measurements are used as independent calibrations to derive temperatures from the density data measured with the BOS system. The results obtained with both systems are used to quantify the dilution behavior of the propagating cloud through a global entrainment parameter b. Its value agrees well with the results obtained by earlier studies.
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