Expansion Coefficients for Orifice Meters in Pipes Less Than One Inch in Diameter

Abstract

A practical technique for using orifices to meter most gases of engineering interest is described. This technique can be employed in pipes less than 1 in. ID, as well as in larger sizes. An analytical expression for the orifice expansion coefficient is developed; this expression includes an empirical factor based on published data for orifice installations in pipes two or more inches in diameter. Experimental verification has shown that the equation gives correct results for the smaller systems and in gases with a specific heat ratio other than 1.3 or 1.4. It is also shown that the empirical equation for orifice-expansion-coefficients which appears in the ASME Fluid Meters Report [1] can be used over a range that includes most gases as well as pipe diameters as small as 1/4 in.