Methods 2, 2F, & 2G: Volumetric Flow Rate Measurement
The ESC Three Dimensional Flow Sensing System and Type S Pitots were used in the flow study initiated by the EPA to evaluate new techniques in improving flow rate measurement under a wide range of flow and swirl conditions. The wind tunnel and field tests used in the study provided a technical basis for three new methods for velocity and volumetric flow rate determination in stacks or ducts, Methods 2F and 2G. At the time of development, the original Method 2 was principally used to ensure isokinetic accuracy through a particulate sampling run by determining average stack velocity under only axial conditions. Method 2 does not include procedures for measuring the yaw angles, pitch angles or wall effects of flow. As such Method 2 can overstate volumetric flow rate when cyclonic flow is present. Yaw angle (side to side), pitch angle (forward to back or vice versa) and wall effects (frictional influence of the stack wall on velocity) characterize the axial component of velocity that exits the stack under cyclonic flow conditions.
The final ESC system designs resulted from performance evaluation during the EPA field tests, recommendations of the test teams who operated the system, requirements specified in the new methods and continuing suggestions from field technicians who operate our systems.