Improved gas flow model for microvalves

Previously, a compact, pressure-and structure-based gas flow model for microvalves was developed. It explained well the flow of gases ranging from 0.01 sccm to 2 slpm (limited only by availability of appropriate mass flow meters). Subsequently, several factors indicated the necessity for improvements to the model. In particular, the effect of value seat periphery length was not accounted for. As a consequence, this work presents a comprehensive yet compact compressible flow model for microvalves, which includes the effects of gas type, ambient temperature, pressure boundary conditions, and all important value structures: valve seat periphery, inlet diameter, and membrane-to-valve-seat gap. The establishment of the model from measured data is described in detail. Projections for high flows in small area microvalves complete the description. The model covers accurately the full range of flow conditions, from seat-controlled flow through orifice-controlled flow. With these attributes, it is widely applicable to microvalves utilizing any form of actuation.