1992 Volume 28 Issue 12 Pages 1411-1418
Discharge coefficients of 9 sonic Venturi nozzles, which have toroidal throats complying with ISO 9300, were measured at the atmospheric condition by a constant volume tank system developed as the primary gas flow standard in Japan. The paper describes the outline of the system, the measuring procedure, and the measured coefficients. The measuring Reynolds number based on their throat diameters ranged from 0.6×105 to 2.4×105, where the boundary layer at the throat is restricted to laminar one. The total uncertainty of the measured coefficients ranged from ±0.14 for the smallest nozzle to ±0.05% for the largest nozzles. The largest and the smallest deviation of the measured coefficients from ISO 9300 are -0.3% at the smallest Reynolds number of the standard and ±0.1% at the largest measuring Reynolds number, respectively. A new fitted curve for the discharge coefficient, which has a steeper gradient than the standard, are proposed within the measuring Reynolds number range.
