Flow Nozzle Meter:  

The flow nozzle meter is simpler and less expensive than a venturi meter, but not quite as simple as an orifice meter.  It consists of a relatively short nozzle, typically held in place between pipe flanges as shown in Figure 4.

Figure 4. Flow Nozzle Meter Parameters

For a flow nozzle meter, the exit diameter of the nozzle, d, is used for D2 (A2 = An), and the discharge coefficient is typically called a nozzle coefficient, Cn, resulting in the following equation:

Due to the smoother contraction of the flow, flow nozzle coefficients are significantly higher than orifice coefficients.   They are not, however, as high as venturi coefficients.  Flow nozzle coefficients are typically in the range of 0.94 to

0.99.   There are several different standard flow nozzle designs.   Information on pressure tap placement and calibration should be provided by the meter manufacturer.