The discharge coefficient of a throat tap flow nozzle based on ASME PTC 6 are measured for Reynolds number range from 1.5×106 to 1.4×107 using the high Reynolds calibration rig in AIST,NMIJ. The discharge coefficients show apparently a dependency of a tap diameter and their behaviors are different from those of PTC 6. A deviation between the experimental results and the extrapolated discharge coefficient according to PTC 6 is 0.37% at Red=1.4×107. To reduce the error in extrapolation, a new type throat tap flow nozzle which has different diameter taps is proposed in this paper. The derived equations of discharge coefficients of this throat tap flow nozzle are determined as a function of Reynolds number and tap diameter based on the experimental results from each different diameter tap. The error of extrapolated discharge coefficient using the derived equations is estimated to be less than 0.1% at Red=1.4×107. The new type throat tap flow nozzle proposed is expected as high accurate flowmeter including the extrapolation for high Reynolds number.
