2 replies to this topic

[gmcgough600]

Hello,

 

I'm looking for some advice, trying to size an orifice plate to limit flow through power station boiler blowdown pipework. I'm using the ISO 5167 equation for mass flowrate:

 

https://wikimedia.or...4a59018e077f166

 

If I can calculate the mass flowrate from the orifice plate size then I can easily iterate this calculation to get a size which fits the flowrate requirements. The problem is that the differential pressure is required, how can I know the differential pressure if I don't know the flowrate? I assume this is determined from the pressure directly upstream/downstream of the orifice? I know the upsteam but not the downstream pressure. The fluid is water.

 

Thanks

Edited by gmcgough600, 04 August 2016 - 05:28 AM.

[Bobby Strain]

Use Excel formulas if you have no programming skill. Or VBA if you know it. You must model the whole system.

 

Bobby

[ryn376]

You will need to calculate the required pressure drop across the orifice. You will need to obtain the upstream water source rpressure and the downstream destination pressure. Then calculate the pressure drop in the piping and fittings based on your required flow rate. Pressure drop across orifice = upstream pressure - downstream pressure - piping pressure drop.