AppEng2
Nuclear
- Oct 24, 2014
- 1
Hi All,
I'm working on an application where there's radioactive waste decomposing in an cast iron container (2.9m^3 volume). The container has a small opening (160mm^2) to diffuse the hydrogen and ideally keep it below the lower flammability limit of 4% volume in air.
Should something go wrong the max pressure created by ignition of the gas (which I am basing on a confined explosion despite the small opening) is 9 bar.
I am trying to confirm that the orifice is large enough to suitably dissipate the pressure, so I guess to do this I need to prove that the flow out of the container is greater than the mass of gas being produced due to the decaying of the material inside.
I know with the pressure difference of 9barg to 1 bara that the flow will be at sonic velocity, I've calculated the gas constant of 4% (2.8% mass) hydrogen, 96% (97.2% mass) air to be 394.34J/KgK.
What I am struggling with is what temperature the gas will be, if it initially starts at 20degC? I've read articles to suggest that a flash fire only lasts up to 3 secs? I thought if I could find the energy created by the flash then I could calculate the temperature difference using Q=mc(T2-T1) but information I've found states Hydrocarbon flash fires have an average heat flux of about 84kW/m2, this is confusing to me because it's about joule/second per m2 and I have a volume of gas.
I suspect there is a simple way of going about this and I have gone off route, so if any one can point me in the right direction it would be greatly appreciated.
Thanks
AppEng2
I'm working on an application where there's radioactive waste decomposing in an cast iron container (2.9m^3 volume). The container has a small opening (160mm^2) to diffuse the hydrogen and ideally keep it below the lower flammability limit of 4% volume in air.
Should something go wrong the max pressure created by ignition of the gas (which I am basing on a confined explosion despite the small opening) is 9 bar.
I am trying to confirm that the orifice is large enough to suitably dissipate the pressure, so I guess to do this I need to prove that the flow out of the container is greater than the mass of gas being produced due to the decaying of the material inside.
I know with the pressure difference of 9barg to 1 bara that the flow will be at sonic velocity, I've calculated the gas constant of 4% (2.8% mass) hydrogen, 96% (97.2% mass) air to be 394.34J/KgK.
What I am struggling with is what temperature the gas will be, if it initially starts at 20degC? I've read articles to suggest that a flash fire only lasts up to 3 secs? I thought if I could find the energy created by the flash then I could calculate the temperature difference using Q=mc(T2-T1) but information I've found states Hydrocarbon flash fires have an average heat flux of about 84kW/m2, this is confusing to me because it's about joule/second per m2 and I have a volume of gas.
I suspect there is a simple way of going about this and I have gone off route, so if any one can point me in the right direction it would be greatly appreciated.
Thanks
AppEng2