Neglecting friction:(adsbygoogle = window.adsbygoogle || []).push({});

I have a four inch diameter pipe that has a constant 8 psi input of natural gas(It is regulated and any psi drop throughout the pipe are negligable in this situation).

I found a site to tell me that the avg natural gas density is 0.4445 kg/m^3 at .06 MPa which I converted to .000016 lb/in^3 at 8 psi. It's close enough for me to assume there is a linear decrease in density v.s. pressure from this point on I suppose - unless that is where I'm going wrong.

This pipe has 'ignitors' which are 1 and 1/4 inch tubes leading into an unpressurized furnace.

I am wanting to also assume, initially at least, that the fire at the end of the tube has no effect (Basically 1 and 1/4 inch holes in the pipe). On other units I can manually set the pressure... and after it ignites, pressure does not noticably change.

I have researched and tried and failed and I cannot come up with mass flow rate through either of the tubes. I've focussed on the Bernoilli equation - but velocity on either side of my equation is unknown.

Any suggestions? A calculation would be a lot cheaper than trying to measure the flow like I have on other units.

Also, Natural Gas is close to 1000 btu per cubic foot so my end result I feel should be around 6 - 30 million btu/hr (mmbtu/hr) output. A Main Burner with huge pipes from a 1 psi 20" source supplys 150 million btu/hr - so it will not be close to that, and a class 2 ignitor by NFPA must be 4 % of that total - so it's not lower than 3 million btu/hr.

Help??? James

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# Process Control Problem

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