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I am trying to write a discrete time simulation of liquid/gaseous oxygen in a pressurised cryogenic fuel tank. For now I am assuming that the only external change to the system is the influx of heat through the radiation. Now my problem is this: For every dt i want to calculate the change in pressure as a result of the change in temperature. But the vapour pressure depends on the temperature, and the temperature changes if the oxygen boils.

I looked into internal energy, and i know that the energy in the whole system should change only by the given heatflux, but i don't understand how i go from this to the pressure and temperature of the system.

So long story short, how do i calculate the equilibrium of a system with a known heat-input?

Thanks.

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To calculate the equilibrium constant of a process,we need to determine the heat change in the process.enter image description here

Ef is the energy of activation for forward reaction and Eb is the energy of activation for the backward reaction.

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  • $\begingroup$ Sounds good, and i am lookin into this right now, but do i understand correctly that i am looking for the state where Rf = Rb and therefore e^(Eb-Ef)/RT ==1 ? $\endgroup$ – David van rijn Dec 7 '15 at 23:28
  • $\begingroup$ No,in an equilibrium state the absolute rate of the backward and forward reactions are equal and not the specific rate of the reactions.Here I have used Rf and Rb for the specific rates and not for absolute rates.Hence,here Rf !=Rb. $\endgroup$ – Ananyo Bhattacharya Dec 8 '15 at 8:43
  • $\begingroup$ Ok, so how do i get from this to the equilibrium of gas and liquid? Ie. moles in gas/moles in liquid. $\endgroup$ – David van rijn Dec 8 '15 at 14:27
  • $\begingroup$ I don't have any idea about that . $\endgroup$ – Ananyo Bhattacharya Dec 8 '15 at 15:43
  • $\begingroup$ Anyway you cannot calculate the equilibrium constant just by knowing the heat input.you have know about the readings after the process or at least the pressures and the dissociation constants. $\endgroup$ – Ananyo Bhattacharya Dec 9 '15 at 11:36

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