Fire case for HC water mixtures

[PLar]

I am calculating relief cases for a system with a water HC mixture. My question is does anyone have a good idée how to calculate the heat of vaporisation for the mixture?
If I take the enthalpy of the mixture in vapour phase (at due point) minus enthalpy of the mixture in liquid phase (at bubble point) I will get some kind of average of the required heat input to evaporate the mixture (and rise the temperature). But the actual heat of vaporisation can change a lot from start to the end.

 

[Chance17]

Having tackeled the same problem in the past, I can tell you
one can get any and all answers based on the physical property set used.
I once tried many different combination using PROII simulator. Never obtained consistency.
Be very skeptical of anyone who claims there is a right method.
My current strategy is to calculate two cases.
One case 100% hydrocarbon.
One case 100% water.
Make sure the safety valve will handle both cases.

 

[pleckner]

A HC-water mixture is no different than any other mixture of differing boiling point components. The initial heat will boil off the lightest component first and so on. You can do a series of flashes, starting off with 1% to get the first HC and then continue from there. The response by Chance17 is essentially the same thing.