I was going through my old diary and found some information I had noted down from a book on Gas Technology I had come across in a library about nine years ago. I don’t recall the title and author of the book but it was one of those out of print old books you get attracted to for some secret/sacred knowledge. :)
The information was about flow of gas in pipes and the simple diagram and explanation there was extremely useful and it helped me throughout my career.
I am recreating the diagram here, hope you will find it useful.
Assumptions:
1) Horizontal pipe, uniform diameter
2) Four pressure gauges attached to points A, B, C and D at equal distances of 8m.
3) When valve E is opened, gas flows in the direction of the arrow.
The information was about flow of gas in pipes and the simple diagram and explanation there was extremely useful and it helped me throughout my career.
I am recreating the diagram here, hope you will find it useful.
Assumptions:
1) Horizontal pipe, uniform diameter
2) Four pressure gauges attached to points A, B, C and D at equal distances of 8m.
3) When valve E is opened, gas flows in the direction of the arrow.
The graph below shows what happens under four different sets of conditions: (Please click on the image to zoom in.)
1) Standing Pressure: When gas is standing still in a pipe i.e. when valve E is turned off, the pressure throughout the whole length of the pipe is the same.
So, pressures at A, B, C and D = 20 mbar
2) Working Pressure: Valve E is turned on to allow a ‘normal quantity’ of gas to flow through the pipe. In this case the pressure drop between point A and B is 2 mbar.
So, pressure at point B = 18 mbar
But, distance between A and B is same as distance between B and C as well as C and D. So pressure loss will be same i.e. 2 mbar.
So, pressure at point C = 16 mbar
Hence, Pressure at point D = 14 mbar
3) Working Pressure with increased quantity: If the quantity of gas flowing is now increased then the pressure loss will also increase. The line 3 shows, with a 40% increase in quantity, pressure loss has doubled i.e. 4 mbar.
So, pressure at point D = 8 mbar
4) Normal quantity with partial blockage: Line 4 shows readings obtained for a ‘normal quantity’ of gas flowing but with an obstruction in pipe between point A and B. This reduces the effective diameter of pipe between point A & B and this has greatest effect on the pressure.
Point B onwards pressure drop is back to normal i.e. 2 bar.
However, the actual pressure drop between point A and B has increased.
Pressure at point D = 4 mbar
Let there be light gas! :)
