Critical Flow of Dense Gases - Modeling and Experimental Validation

The critical mass flow of dense gases strongly depends on real gas effects. In the present work the detailed assessment of the critical flow conditions and the limiting mass velocity in the flow of refrigerants has been experimentally verified. Critical flow function C* data for R-410A and R-507A have been predicted based on Martin–Hou equation of state. The computational study was assured by implementation of theoretical model [1] for one dimensional (1D) and non-linear gas dynamic problems. This model, with the corrections for the boundary layer (BL) displacement thickness, gives a better prediction of the critical flow function than classical approach. Appropriate sonic flow conditions have been executed in the pressurized closed loop system by using ISO 9300 critical Venturi nozzle. Measurements of critical mass flow for dense superheated vapour of R-410A and R-507A carried out on laboratory test stand have confirmed the accuracy of the model and its physical significance. A main result of the investigations is a set of graphs C*(T0, p0) and tables for an assumed range of stagnation temperature T0 and pressure p0 at the upstream flow.