Visit regularly for more free engineering spreadsheets.To calculate the flowrate of a fluid passing through an orifice plate, enter the parameters below. You'll find a spreadsheet that models a liquid orifice meter here. Varies the guess value of Re until it matches the calculated value ofīy carefuly altering the equations (and the parameters used by Goal Seek), you could also solve for any other variable - for example, you could find the pressure drop for a specific flowrate (let me know if you need help in implementing this). The spreadsheet provides an initial guess value for Re. This process is automated with a button - just fill in the parameters, click a button, and some VBA initiates Goal Seek with the correct settings Excel's Goal Seek functionality is used to iteratively solve the equations for the flowrate. The calculation is iterative: you need Re to calculate C, you need V to calculate Re, but you need C to calculate V. This is a screen grab of part of the spreadsheet. The equations use the ideal gas law to calculate the gas density (you could override this with your own value), and are only valid for pipes with internal diameters from 50 mm to 1000 mm, and for pressure ratios greater than 0.75. For corner taps, L 1 = L 2= 0, for D-D/2 taps L 1 = D 1 and L 2= D 1/2, and for flange taps L 1 = L 2= 1 inch. There are three standard tap positions that determine the values of L 1 and L 2, as illustrated below. A o is the cross-sectional area of the orifice (m 2).R is the gas constant (8314 J kg -1 k -1).V is the gas velocity in the pipe (m s -1).D 1 and D 2 are the pipe and orifice diameters (m).P 1 and P 2 are the upstream and downstream pressures (Pa).L 1 and L 2 are the upstream and downstream tap positions (m).C is the discharge coefficient (only valid for the three standard tap positions given below).These are the equations implemented in the spreadsheet (as specified in ISO 5167) and high Reynolds numbers (>10 4) are required for the greatest confidence in their accuracy, and the resulting pressure drop can be significant.Īccordingly, orifice meters are only used with the pressure drop is not critical, and accuracy is around 2% at best.accurate values of the physical parameters are required,.The relationship between flowrate and pressure is non-linear,.While orifice meters are cost effective, they have several disadvantages. Orifice meters use the pressure loss across a constriction (that is, the orifice plate) in a pipe to determine the flowrate. This Excel spreadsheet calculates the flowrate from the pressure drop across a gas orifice meter with the equations defined in ISO 5167.

Orifice plate pressure drop calculator