Air ingress into a furnace vessel

1. Jun 24, 2015

fluxfire71

If a furnace at 500 Celcius and 500 bar was to lose pressure from a breach (pipe break) resulting inert gas escaping the furnace would loose pressure and reach equilibrium pressure with outside room pressure.

When equilibrium pressure is reached how would the outside air enter into the furnace. I'm struggling to understand the driving force for air to move into the furnace.

Finaly how would one calculate such a thing?

Regards

Flux

2. Jun 26, 2015

insightful

Air would enter by diffusion. Look up Fick's laws of diffusion.

Air would also enter if the furnace cooled down and the gas inside contracted.

Air would also enter via changes in barometric pressure and the furnace "breathing."

3. Jun 29, 2015

fluxfire71

If there is a significant thermal gradient i don't think the mixture of gas and air will return through the furnace breach assuming the furnace heating element is still engaged.
The gas expansion into the room will take some of the furnace energy but not a significant in comparision to the the stored thermal energy. (Basically the furnace will be much hotter than the outside)

I the case where the heating element was to fail the furnace will cool if i know the cooling rate i.e. J/sec lost, how could i use this information to work out the mass flow of air into the furnace?

Much appreciated

Flux

4. Jun 29, 2015

insightful

Estimate the mass and heat capacity of the furnace to get the temperature drop, then use V1/V2 = T1/T2 with T in Kelvin to get the volume of air pulled in. Then use the density of ambient air (about 1.2 kg/m3) to get the mass of air pulled in.