Experimental investigation on the optimum geometry of an S-type Pitot tube for GHG emission monitoring

The S-type Pitot tube is a popular device used to conduct periodic volumetric flow rate monitoring performance tests in stacks or ducts. To control the accuracy of the S-type Pitot tube coefficient, all factors resulting in errors must be estimated. However, there are no detailed guidelines in international standards regarding the geometry of the S-type Pitot tube. Thus, in this study, the characteristics of S-type Pitot tubes with various geometries were tested in the Korea Research Institute of Standards and Science (KRISS) standard air speed system to determine an optimal shape for the S-type Pitot tube for measuring the volumetric flow rate in smokestacks. The results revealed that S-type Pitot tubes with a long opening distance are inclined to stability and insensitive to yaw and pitch misalignments. Finally, it was found that an S-type Pitot tube with a bending angle of 30° has a stability coefficient distribution curve. (paper)