IHS ESDU Compressible flow of gases. Pressure losses and discharge coefficients of orifice plates, perforated plates and thick orifice plates in ducts. 82009

ESDU 82009 provides pressure loss and discharge coefficient data for subsonic compressible flow of gases through single, or multiple, sharp-edged orifices in thin or thick plates for flow rates up to choking. The mechanics of compressible flow through orifices are discussed briefly with particular attention to sonic flow conditions. The mass flow function, based on orifice entry conditions, that gives maximum mass flow rate is defined and pressure loss coefficients are then expressed as a function of the ratio of the actual mass flow function to that limiting value. All are functions also of porosity and thickness/diameter ratio of the orifice. The data cover a range of porosity between 0.001 and 0.95 and thickness/diameter up to seven. Discharge coefficients are presented for orifices of very small porosity, for maximum mass flow conditions and for conditions when the total-pressure loss coefficient exceeds unity. Although the data were derived for symmetrical arrangements of circular holes in circular plates they can be applied reasonably well to square ducts, square holes and small departures from symmetry. A computer program, ESDUpac A8209, is provided.