Critical Orifices Research Articles

STUDY OF OPERATING PERFORMANCE OF A CRITICAL ORIFICE OF THE HEXHLET GRAVIMETRIC DUST SAMPLER.

A simple assembly for the measurement of volume flow-rate in the Hexhlet dust sampler is described. The operating performance of seven critical orifices at different vacuum values is presented in graphical and tabular form.

A TECHNIQUE FOR CONSTRUCTION OF PREDICTABLE LOW-CAPACITY CRITICAL ORIFICES.

Abstract A rapid, inexpensive technique is described which utilizes stainless steel hypodermic needles as low capacity critical orifices. A range of needle sizes is available and manufacturers' quality controls ensure reproducible results.

Review of Critical Flowmeters for Gas Flow Measurements

Critical flowmeters for accurately measuring the mass flow rates of nonreacting real gases were reviewed. Discussions were presented on theoretical flow functions, on parameters for correlating discharge coefficients, and on the importance of real gas properties. The performance characteristics of critical nozzles and orifices of several designs were reviewed. Approaches were discussed to problems which must be researched before the fullest potential of this type of flow measurement can be realized.

The construction of critical orificies working with small pressure differences and their use in controlling airflow.

The use of the critical orifice to stabilize the flow rate of a gas is well known. It has been used, for example, in environmental studies in industrial hygiene to stabilize the flow of air through sampling circuits, while in the impinger the impaction jet can be run under critical flow conditions to give a sonic jet for impaction purposes and at the same time a controlled sampling rate. Many authors have investigated experimentally and theoretically the discharge of gas through an orifice. Saint-Venant and Wantzel (1839) first obtained the equations of discharge by assuming that an adiabatic type of pressure-volume relation ship was applicable under the conditions of flow. They obtained the relationships :?

An Accurate Gas Metering System for Laminar Flow Studies

The design and performance of an accurate flow system utilizing critical velocity orifices is described. Results indicate that an absolute accuracy of three parts in a thousand is realized over a flow range of 0.002 to 2 cubic feet per minute. Calibration of the flow system was accomplished by means of a specially modified and carefully standardized wet test gas meter. Descriptions of the components of the flow system and of subsidiary calibrating equipment are presented. Critical flow orifice discharge coefficients are found to be independent of the type of gas; however, because of gas impurities, prediction of relative rates of flow of various gases through an orifice by use of theoretical relationships is uncertain, and experimental data are given to illustrate this.