acurate pressure drop measurement

[themroc]

We need to meassure the pressure drop in a single vertical tube. tube diameter is about 45mm, tube l;ength 2.5m. On the wall a liquid film is flowing down by gravitational force. The film is water like only 1 to 2mm thick. In the center flows an air flow. From this flow we need to meassure the pressure drop. The Re No is about 20000 to 60000.
Because of the liquid flow at the wall bore holes are not possible.
So the idea is to insert 5mm tubes at the inlet and outlet of the tube from outside the tube till the centerline and measure the pressure. Would this work?
Is there any requirement for the tip of the 5mm tube. I pressume it does not need to be bend, because in case it is bend we are going to meassure not the pressure drop, than it would act like a pitot.

 

[dcasto]

If you are looking for just the pressure drop, go ahead and just tap the line and read the pressure at the two taps. The falling film has no bearing on the line pressure.