Orifice Calculations: Convert Pressure Difference to Mass Flow Rate

[almarzooq]

Hi there,

I have used an orifice for my project to measure the pressure difference and hence the mass flow rate of air going through a pipe of 26 mm diameter. i kept changing the flow from max to min and ended up with values of pressure diference. The questions here is how to convert thses values ( in meters) into mass flow rate (kg/s) ?? I tried to find equations for this but they have the coefficient of discharge involved and i cannot find this value ! can anyone help me on this please ?

regards

 

[FredGarvin]

If it is a square or sharp edged orifice, the starting point for Cd is 0.6.

 

[almarzooq]

thanx a lote , can please post the equation to find the mass flow rate here and explain its parameters and variables ?

 

[FredGarvin]

http://www.pipeflowcalculations.com/orifice/theory.htm

This will give you volumetric flow rate, but I am assuming that you can calculate mass flow from there.

By the way, for anyone else interested, this reference gives the polynomial expression for calculating Cd based mostly on beta ratio and Re. This is referenced in the ASME spec on orifice calculations. I haven't found it stated anywhere else yet. It's a nice piece of information.