Venting Channel Research Articles

A small-size silicon microphone for measurements in turbulent gas flows

Abstract For the first time a silicon microphone specially designed for measurements in turbulent gas flows has been fabricated and tested. The new design, based on surface-micromachining techniques, has a very small pressure-sensitive polysilicon diaphragm of 100 μm side length and 0.4 μm thickness with polysilicon piezoresistive strain gauges. The small diaphragm makes it possible to resolve and measure the pressure fluctuations of the smallest eddies in a turbulent flow. In order to achieve a sufficiently high acoustic pressure sensitivity, a relatively deep (3 μm) cavity is formed below the diaphragm by using the sacrificial-layer etching technique. A special vent channel is designed to give an equalization of the static air pressure between the cavity and the ambient without degrading the dynamic pressure response of the microphone. The device has a very flat frequency-response curve within ±2 dB between 10 Hz and 10 kHz and an acoustic sensitivity of 0.9 μV Pa−1 for a supply voltage of 10 V. It has been shown that the new sensor fulfils the requirements for pressure measurements in turbulence. The microphone frequency response has been calculated using an electrical analogy. Comparisons with experimental data are presented.

Microplate-Radioluminography, a Substitute for Liquid Scintillation Counting.

A method alternative to liquid scintillation counting (LSC) for detecting β emitters was developed. The new method involves putting an aqueous 14C sample onto the flatt-bottomed wells of a polystyrene microplate, drying the sample and determining the radioactivity using radioluminography (RLG). It provides a simple, inexpensive and reliable technique for determining the radioactivity of a few hundred samples simultaneously. 3H can be determined by using a microplate having wells interconnected with shallow vent channels and exposing in helium atmosphere. 32P can be determined by placing the sample planchettes in shielding adapter made of brass, which prevents each sample from cross-talking. This method was also applied to an off-line counting of 14C in HPLC eluate. A succession of aliquots of the eluate were collected directly in the wells of microplates and evaporated to dryness. The detection limit was 0.35 Bq per injection. The RLG off-line counting method was utilized to determine [14C] EPA metabolites formed by rat hepatic microsomes. Radioluminography, microplate, liquid scintillation counting, β emitters, cross-talk, off-line counting of HPLC eluate, EPA A substitute for liquid scintillation counting, a simple, inexpensive, sensitive and reliable technique for determining β emitters, applicable to off-line counting of HPLC eluate.

Safe operating conditions research for hydrogen systems with gas venting

Abstract A one-dimensional mathematical model has been developed for the instationary regime. It describes the process of air penetration into the gas venting pipe and characterizes the concentration distribution inside the venting channel. Air penetration into hydrogen venting pipelines having diameter 0.032–0.2 m with horizontal, up and down exit section directions, at gas venting temperatures 77–300K has been experimentally investigated.