S-Pitot Tube for Measuring Bi-Directional Air Flow

It seems that air/gas flow in either direction will cause readings on both ports. One positive and the other negative. Is the flow turbulent or smooth? Why not make the pitot openings at a 90 deg angle to the flow instead of 45 deg? Maybe I don't understand how you intend to measure the pressure generated.

Contact Dwyer- one of the first/ best companies, expert on air flow.

I have used a similar technique when measuring low velocities in industrial process air streams. If you connect one impulse pipe to the high pressure connection of an electronic differential micromanometer and the other to the low pressure connection, you will get twice the velocity pressure and the duct pressure will have been cancelled out by being on both sides. Measure the duct temperature and do the normal arithmatic using half the measured differential pressure and you should get a reasonable approximation to the flow rate.

If you use two properly profiled pitot tube tips positioned on the same plane through the duct you will get the best result. It should be possible to get 1mm OD stainless hypodermic tube on the internet. Produce 2 tubes with a radius on the tip and bend them a 90° so that the radiused end is about 10-15 diameters long and then mount both on a plate fixed to the side of your duct.

Ideally you should calibrate the system against a known standard, say a rotating vane anamometer with a calibration certificate.

Good luck and have fun.

Stuart