Standard Venturi nozzle
The standard Venturi nozzle is a differential pressure measuring instrument whose geometric dimensions, surface quality, and installation conditions meet the requirements defined by DIN EN ISO 5167-3. The profile is rotationally symmetric and comprises a cylindrical throat, diffuser, and narrowing inlet with rounded profile that are identical to the orifice of a standard nozzle. See Fig. 1 Standard Venturi nozzle
The flow volume is calculated based on the differential pressure level measured and the flow coefficient (C) using the formula for differential pressure measuring instruments. The flow coefficient is depicted in a table in appendix A3 of DIN EN ISO 5167-3.
The overall pressure losses of the standard Venturi nozzle are considerably lower than with a standard nozzle of the same nominal diameter and diameter ratio. The lengths of the inlet sections, however, correspond to those of the standard nozzle.