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Old   March 20, 2014, 04:23
Question Sensible Enthalpy
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Hi!
I am a new user and also a new learner of Open Foam and I need some help.

I am working on the Fuel Injection Model of Diesel Engine and I have some problem related to Evaporation of Urea and Water. I am using Open Foam 2.1 . I have a problem with the cooling temperature as it cool the vapors more and did not evaporate the Urea Properly. Its a Steady State Model.
And for Urea i am using "SingleKineticRateDevolatilisation Model".


I come to one Energy Equation related to Sensible Enthalpy and did not understand what is this Code mean and how it works.

The Term is "Parcels.Sh(he)"

Can any one tell me
1. what this term do to the system and on which factors its depends upon and details if possible.
2. What is the Influence of the temperature on this.
3. Do i have to add, Multiply or Divide any value with it to make it work properly.

Thanks and your reply would be really appreciated
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Old   March 20, 2014, 11:55
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Marco A. Turcios
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Sh(he) is the source term for enthalpy derived from the parcels. It accounts for evaporation and phase change of the spray and the thermo model of the continuous phase, and it shouldn't require any manipulation for it to work properly, assuming you have set up your model correctly. I saw another thread you have asked about the spray model, so I will post a reply there and continue the discussion.
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Old   March 21, 2014, 04:43
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Hi Marco,

Thanks for your reply. yes you are right it is the source term for Enthalpy but my evaporation is not cooling down properly means if i do some changes in Physical Properties its good but then when i change the mass flow rate with some factor 10 or other it gave the temperature drop really different which is not right. So that's why i ask may be there is some thing i have to do with this Parcel Sh(he) term to make it work correctly.???? WHAT YOU THINK ANY SUGGESTION
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Old   March 21, 2014, 09:08
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Quote:
Originally Posted by brbbhatti View Post
So that's why i ask may be there is some thing i have to do with this Parcel Sh(he) term to make it work correctly.
Sure, the source term in the enthalpy equation has to reflect the heating/cooling due to condensation/evaporation. But you would not modify the Sh source term itself, meaning in somehow in the top-level solver!

If you implement your evaporation/condensation model correctly, you don't have to worry about Sh at all. Have a look at the 'LiquidEvaporationBoil' class and specifically the 'dh' function.

If you want to implement your own PhaseChange model, see here how to do it:
http://www.cfd-online.com/Forums/ope...tml#post480698

And please, don't spread this discussion over several threads!
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combustion model, energy equation, enthalpy, mixture evaporation

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