Accurate flow metering of hazardous gases used in semiconductor fabrication is essential for optimizing device production and yield. The development of metering standards requires accurate thermophysical property data and reliable property models. However, measurements on these gases are challenging due to their hazardous and often corrosive nature. We have developed a multi-faceted approach to measure and model the speed of sound and viscosity of these gases. For non-hazardous gases, a spherical acoustic resonator capable of sound speed measurements with uncertainties lower than 0.05% is used. For hazardous gases, we are developing a cylindrical acoustic resonator constructed entirely of Monel. The speed of sound data are used to derive key thermodynamic properties using fundamental thermodynamic relations and robust equations of state. We are also developing a Greenspan acoustic viscometer to measure viscosities. The acoustic viscometer is advantageous for measurements on hazardous gases as it does not require continuous fluid flow, has no moving components, and is constructed with Monel wetted parts. This talk highlights the design of the viscometer and the network impedance model used to extract viscosities from acoustic resonance data. Finite element methods are used to guide and describe the design criteria of both the cylindrical resonator and the viscometer.
Al‐Barghouti et al. (2025) studied this question.