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# How to determine the correct Enthalpy

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Recently, I have build a model by tough2

I want to simulate a case that described the geothermal fluid inject to fracture rock.

The fluid temperature is about 190~280 ℃， and the rate is about 3E-5 kg/s;

How can i determine the enthalpy if I use INJECTION?

I have tried many enthalpies, some will lead to model abnormal, and some only last a low temperature.

Thanks

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Just now, XiaoMao said:

Recently, I have build a model by tough2

I want to simulate a case that described the geothermal fluid inject to fracture rock.

The fluid temperature is about 190~280 ℃， and the rate is about 3E-5 kg/s;

How can i determine the enthalpy if I use INJECTION?

I have tried many enthalpies, some will lead to model abnormal, and some only last a low temperature.

Thanks

In addition, I wish I can know what the differences between heat in and Enthalpy

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I would recommend that you take a look at a steam table (assuming you are injecting water) to get an idea of enthalpy at various pressure and temperature combinations.

I am not able to post links on this website, but if you do a Google Search for "spirax sarco steam table", you should be able to get to a series of online calculators.

If you are trying to inject at a constant temperature, you should know that the enthalpy needed to maintain a specific injection temperature changes with pressure.  So, it can be tricky to inject at a constant temperature in TOUGH2.  One option would be to anticipate the enthalpy changes needed to maintain a temperature as pressure goes up and down (and vary it with time).

You can also assigning a very large density such as 1e40 (this gives the material a very large heat capacity).  If you do this, then the fluid leaving the injection cell will always have the same temperature as the initial temperature of the injection cell.

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4 hours ago, Alison said:

I would recommend that you take a look at a steam table (assuming you are injecting water) to get an idea of enthalpy at various pressure and temperature combinations.

I am not able to post links on this website, but if you do a Google Search for "spirax sarco steam table", you should be able to get to a series of online calculators.

If you are trying to inject at a constant temperature, you should know that the enthalpy needed to maintain a specific injection temperature changes with pressure.  So, it can be tricky to inject at a constant temperature in TOUGH2.  One option would be to anticipate the enthalpy changes needed to maintain a temperature as pressure goes up and down (and vary it with time).

You can also assigning a very large density such as 1e40 (this gives the material a very large heat capacity).  If you do this, then the fluid leaving the injection cell will always have the same temperature as the initial temperature of the injection cell.

Thank you very much!

I will try to modify the parameters according to your recommend.

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4 hours ago, Alison said:

I would recommend that you take a look at a steam table (assuming you are injecting water) to get an idea of enthalpy at various pressure and temperature combinations.

I am not able to post links on this website, but if you do a Google Search for "spirax sarco steam table", you should be able to get to a series of online calculators.

If you are trying to inject at a constant temperature, you should know that the enthalpy needed to maintain a specific injection temperature changes with pressure.  So, it can be tricky to inject at a constant temperature in TOUGH2.  One option would be to anticipate the enthalpy changes needed to maintain a temperature as pressure goes up and down (and vary it with time).

You can also assigning a very large density such as 1e40 (this gives the material a very large heat capacity).  If you do this, then the fluid leaving the injection cell will always have the same temperature as the initial temperature of the injection cell.

Actually, I am trying to simulate a vapor dominated system.

I wish I can inject Steam (Temperature =250~300C, Pressure =1.5 Mpa) to my system.

In that way, I can observe the mixing process of the hot steam and cool groundwater and get the evolution of phase change.

By the way, how should I set the boundary condition if I want to inject a mixture of gases, including CO2, water steam, H2S?

Can I use the chemical zone in toughreact ?

Thank you very much!

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