PTS Flowbench Forum

Hello to everyone,

this is my first posting here an I hope it's not in the wrong section.
How can I calculate the flow of a testing piece, when I have a water gage without a percent scale. Does anyone know the formula for this?
For example, if I use a 1,6" sharp edged orifice plate and have a reading of 8,7" @ a depression of 10", what cfm number would that be?

Michael

Sure, look that the spreadsheet from THIS THREAD, it'll do the calculation for you or, if you look at the section labelled "Range calculation explanation" is explains, in detail, the math using by the spreadsheet.

And if you want, the spreadsheet will also do all the calculation needed to create your own percent scale.

Thank you for pointing this out, I have already downloaded your spreadsheet before, but I 've missed that it contains this information. In my example I have to multiply the square root of my manometer reading by 34,615 (combined coefficients * orifice area) to get the right result very quickly.

Cheers

Michael

For example, if I use a 1,6" sharp edged orifice plate and have a reading of 8,7" @ a depression of 10", what cfm number would that be?

Michael, Welcome!

In your above example one would need to know what the angle of the incline is, its rise and the linear scale of the incline. With this information we use basic Trigonometry to calculate the Delta P (Incline reading in rise). Hope this helps

Rick

Rick,

I'm currently using a U-tube manometer, so i can read Delta P directly. Thanks anyway for your advice.
For my new bench (plans already ordered ) I will make an inclined manometer with a percent scale. I used my old bench just to compare mods on a port to previous state. But I was curious to know roughly in which cfm range my ports are.

Michael

Hi,

I wonder if anyone was using this nice excel file I found on the old tractorsport forum: http://tractorsport.com/download/Orificeflowinapipe.xls

I have some questions regarding it:

The fluid density, rho1, is it A:the density of the ambient air, or B the density of the air in the collector (between head and orifice)
If it is A, how can the actual massflow be calculated as the file only needs the pressure differential p1-p2 over the orifice, and not the absolute pressure p1
How is the value in cell J38 calculated without knowing the absolute value of p1?