90.92 Standard to be revised Nov 7, 2024
ISO
ISO/TC 30/SC 2 Pressure differential devices
International Standard
17.120.10 Flow in closed conduits
This document specifies the geometry and method of use (installation in a system and operating conditions) of critical flow nozzles (CFNs) used to determine the mass flow rate of a gas flowing through a system basically without the need to calibrate the CFN. It also gives the information necessary for calculating the flow rate and its associated uncertainty.
This document is applicable to nozzles in which the gas flow accelerates to the critical velocity at the minimum flowing section, and only where there is steady flow of single-phase gas. When the critical velocity is attained in the nozzle, the mass flow rate of the gas flowing through the nozzle is the maximum possible for the existing inlet condition, while the CFN can only be used within specified limits, e.g. the CFN throat to inlet diameter ratio and Reynolds number. This document deals with the toroidal- and cylindrical-throat CFNs for which direct calibration experiments have been made in sufficient number to enable the resulting coefficients to be used with certain predictable limits of uncertainty.
WITHDRAWN
ISO 9300:2005
PUBLISHED
ISO 9300:2022
90.92
Standard to be revised
Nov 7, 2024
IN_DEVELOPMENT
ISO/AWI 9300