An Investigation of Single-Phase Incompressible Flows Through Rectangular Micro-Constriction Elements

Abstract

Incompressible flow through constriction elements (orifices, nozzles and venturis) are commonly encountered in several macro and micro scale engineering applications.. The current research endeavor experimentally investigates single-phase incompressible flows of de-ionized water through rudimentary micro-constriction configurations such as rectangular slot micro-orifices entrenched inside microchannels. Additionally, the effects of micro-orifice and microchannel size on the discharge in single-phase flows have been evaluated, and experimental data suggests that the flow rate is dictated by the constriction element opening rather than the microchannel area. The discharge coefficients associated with incompressible flows through multifarious micro-orifices have been estimated, and the effects of Reynolds number, micro-orifice size and microchannel area on the discharge coefficients have been explored. The discharge coefficients are calculated based on standardized D-D/2 (One channel diameter upstream and half channel diameter downstream) pressure tap specifications, and can be directly employed in the design of micro-valves and other micro-constriction devices. Furthermore, experimental results indicate that the discharge coefficient rises and peaks at a critical Reynolds number (200 ≤ ReCrit ≤ 500), which indicates the emergence of turbulence immediately downstream of the micro-orifice and re-laminarization further downstream. The discharge coefficient stabilizes and reaches a steady value after the critical Reynolds number has been transgressed. Finally, a correlation for the discharge coefficient, which includes the Reynolds number and the ratio between the hydraulic diameter of the micro-orifice and the microchannel, is presented to aid designers of MEMS devices involving micro-constriction components.© 2005 ASME