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# Enthalpy Discrepancy

Hello There,

I was just wondering what the reference state for the enthalpy of water in TOUGH2 is? The reason is I would like to define water infiltration (precipitation) with a temperature of 20˚C. Therefore, I ran a single element in TMVOC initialized with only water at atmospheric pressure and a 20˚C, and I got 8.4 J/kg as the enthalpy. Also, I get roughly similar number in NIST chemistry webbook. However, if I use this number, I noticed the temperature in the elements drops and goes below 20˚C. So, I came across a publication where an enthalpy of 9.4e4 J/ kg corresponding to 20˚C was used. Now, when I use that number I get the right temperature of 20˚C. I suppose it might be due to a discrepancy in the reference temperature. Could anybody explain this please? How should I calculate the right enthalpy corresponding to a given temperature (say 20˚C) to be used in TOUGH2?

Thanks,

Alireza

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• Dear Alireza,

The best way to inject liquid (or gas) at a fixed temperature is to attach a virtual grid block to the block that you want the fluid injected into.  Give this virtual grid block a rock type with an infinite (or very large) density and whatever initial temperature you want your injected fluid to be.  Then when you inject your fluid into the virtual block, the fluid will equilibrate with the block temperature and fluid of that fixed  temperature will flow into your actual injection grid block.

This approach works for both gases and liquids.  The reason this is necessary is that you cannot know a priori the enthalpy of the injected fluid because you don't know a priori what its pressure will be upon injection.

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• Alireza
• Alireza
• 4 yrs ago
• Reported - view

Curt Oldenburg Thanks Curt for your reply. I understand the procedure you mentioned except how to define a virtual grid block? what exactly you mean by virtual block? I'm doing a 2D modelling in TMVOC using petrasim and the NAPL leak point is somewhere in the middle of the domain. So, how to define a virtual grid block attached to that? could this method also work when defining a water infiltration mass rate for an entire layer (with several grid blocks) in a thermal modelling?

Thanks again,

Alireza

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• JuDi
• JuDi
• 4 yrs ago
• Reported - view

Alireza ,

if you are using Petrasim, check the manual regarding "Extra Cell" (under the "Solution Mesh" section). And yes you can add those in the middle of the mesh/domain, you just need to define a CONNE from this extra cell to the cell from the real mesh.

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• Alireza
• Alireza
• 4 yrs ago
• Reported - view

JuDi

Thanks very much JuDi, much appreciated.

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