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# How to consider the evaporation effect of water affected by temperature in tough2

How to consider the evaporation effect of water affected by temperature in tough2 (or what is the governing equation of water conversion in liquid and vapor)?

I can't find related description in the manual.

Thanks！

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• Dear Sue,

The partitioning of water into liquid and gaseous phases is determined by steam tables, which are built into TOUGH.  For a given temperature and pressure condition in a grid block, how much of the water component is in the liquid phase and how much is in the gas phase is determined by interpolating from the steam table.  So there is not a governing equation describing conversion of liquid to vapor per se.  I remember one time long ago I wanted to determine the boiling rate for a geothermal problem, and I tried to do it as a  post-processing step, by inferring it from the change in phase saturation over time.  Other TOUGH users may have experience doing something similar, and I invite them to share their approach.

Christine

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• Manuel Rivera
• Geothermal reservoir engineer at Mercury NZ Ltd.
• Manuel_Rivera
• 1 yr ago
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For a particular enthalpy and pressure/temperature conditions in a grid block, the steam tables say there is only one steam fraction value associated.  If either enthalpy or pressure/temperature change in time from mass and energy balance calculations, then steam fraction (Sg) will change accordingly. There is no explicit governing equation that describe steam fraction changes, because it is actually calculated through a set of coupled mass and energy balance equations for each block, which are presented in the TOUGH2 manual.  Look for the steam phase saturation  variable in them.  Hope it helps.

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• Christine Doughty said:
Christine

Thanks，but where can I found the steam table file used in TOUGH , it is hard to read IAPWS-R6-95.

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• sue

In the TOUGH3 source code, open file thrm.f90 and look for subroutine sat and the subroutines it calls.

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• I also see this part in the TOUGH_3 Users Guide V2. Does it mean the  latest version of TOUGH is able  to simulate evaporation?

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• All versions of TOUGH can simulate evaporation. The instructions you show give three options for how to specify a evaporation at the ground surface. More details on this topic may be found in the TOUGH short course training material. Go to https://tough.lbl.gov/events/tough-short-courses/ and scroll down to Training Material and download the following. Look at the material starting on page 91.

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• Christine Doughty Could you share the steam table file? I use Petrasim instead of TOUGH2, so I couldn't find it. Thanks a lot.

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• Dear Sue,

I am hesitant to send you the source code for the subroutine that calculates saturation pressure as a function of temperature in TOUGH3, because it is not designed to be used in stand-alone mode.  It calls other subroutines and uses several modules.   You will need experience programming in Fortran to modify it to do what you want.  But if Petrasim provides the TOUGH3 source code, I will tell you where to look.  Let me know.

As an alternative, there are many forms of the steam tables on the internet that are in a more user-friendly form than IAPWS-R6-95.  When I searched for "steam tables" or "steam table calculator" I got many promising looking hits.

Christine

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