Incompressible and compressible flows through rectangular microorifices entrenched in silicon microchannels

Abstract

Incompressible and compressible flows through indispensable configurations such as rectangular microorifices entrenched in microchannels have been experimentally investigated. The current endeavor evaluates the effects of microorifice and microchannel size, estimates the discharge coefficients associated with both compressible and incompressible flows, examines the contraction coefficients, probes subsonic and supercritical gas flows, and explores the presence of any anomalous effects such as those reported for microchannels. The discharge coefficient in incompressible flow, using deionized (DI) water as the working fluid, rises and peaks at a critical Reynolds number, (200/spl les/Re/sub Crit//spl les/500). The reported range of the transitional Reynolds number compares favorably with the values observed in conventional scale studies and suggests the absence of any irregular scaling effects. Furthermore, nitrogen flows through various microorifices suggests that the constriction element rather than the microchannel area determines the flow rate. Additionally, the critical pressure ratio at choking is close to the isentropic value (0.47/spl les/(P/sub 2//P/sub 1/)/sub Crit//spl les/0.64) and no anomalous scale or slip effects have been observed. Unlike macroscale compressible flows through an orifice, the losses seem minimal and the discharge coefficients are close to unity. The geometry acts as a smooth converging-diverging nozzle and the mass flow rate trends appear similar to the data obtained in micronozzle flows.