Primary calibrations of critical flow venturi nozzles in high-pressure gas

Performance evaluation tests on a set of five critical flow venturi nozzles are reported. These nozzles were tested in the new gravimetric gas flow standard test rig and a description of this unique rig is included. The experimentally determined nozzle discharge coefficients are compared with those obtained in calibrations on similar nozzles against basic reference standards, undertaken at other laboratories and they are also compared with theoretical values. Some consideration is given to the effects, on the nozzle discharge coefficient, of the temperature gradient between the nozzle wall and the main gas stream at the sonic throat.