Effect of high beta values on mass flow through critical flow nozzles

In a previous work (Stewart et al., Flow Measurement and Instrumentation 10 (1) (1999) 27-34) the authors presented improved calculations for the mass flow of a gas through a critical flow nozzle. The work in Stewart et al. is applicable only when the nozzle throat to pipe diameter ratio, beta, is lo w (<0.15). Whilst it is preferable to use a critical flow nozzle with a low beta, practical considerations may dictate otherwise. This work extends th e calculations to include high beta values, explaining the problems encount ered in these situations and the procedure for calculating the mass flow ac cordingly. The same four gases are covered, dry CO2-free air, nitrogen, arg on, and methane. A new empirical correction factor for use with high beta c ritical flow nozzles is presented which, when combined with the work in Ste wart et al., provides an accurate yet simple method for calculating the mas s flow of these gases through critical flow nozzles with a wide range of be ta values. (C) 2000 Elsevier Science Ltd. All rights reserved.