How to add a ionic solution and a Clay Material in ANSYS CFX?

lordluan · June 11, 2019, 15:30

I am trying to study a system in which a solution (PbSO4+Water) flow through a porous domain (The Clay mencioned in the title), but I don't know how to add these materials.
About the solution, I added the PbSO4 and Water and then created a new material treating it like a variable composition mixture (Since there will mass transfer in the study), but there wasn't any option to add the mass fractions. Do you think it's an wrong way of solving the problem?
I was wondering if I can do the same with the clay.

ghorrocks · June 11, 2019, 20:33

How to add them depends on what you are trying to model. So what are you trying to model? What are the important physics and chemistry?

lordluan · June 11, 2019, 20:51

Thanks for replying.
I am trying to model the adsorption of Pb2+ in Clay. The system is a column with clay (fixed bed reactor), the solution with Pb2+ enters the column from bellow and as the solution percolates the Clay, the Pb2+ is adsorbed.
I've looked the CFX tutorials but I couldn't find anything similar.

Gert-Jan · June 12, 2019, 09:23

My main concern is that the liquid flows through your pack bed (probably) like simple plug flow. No interesting flow phenoma occurs that justifies the use of CFD. Unless you want to model it on grain level. But I don't think so. Therefore, I always ask: "What question are you trying to answer using CFD"?

The only interesting thing is the adsorption kinetics and the prediction of the breakthrough. If you want to understand the concentration profile, you'd better model that using a PDE solver (Matlab, PDESOL, or similar) dedicated for adsoprtion processes. Don't think that CFD is suitable for this. You overestimate the capabilities of CFX in this respect.

lordluan · June 12, 2019, 09:34

Quote:

Originally Posted by Gert-Jan

My main concern is that the flow flows through your pack bed in probably like simple plug flow. No interesting flow phenoma occurs that justifies the use of CFD. Unless you want to model it on grain level. But I don't think so. Therefore, I always ask: "What question are you trying to answer using CFD"?

The only interesting thing is the adsorption kinetics and the prediction of the breakthrough. If you want to understand the concentration profile, you'd better model that using a PDE solver (Matlab, PDESOL, or similar) dedicated for adsoprtion processes. Don't think that CFD is suitable for this. You overestimate the capabilities of CFX in this respect.

This problem was already solved using CFD. But the authors of the article used ANSYS Fluent, I'm trying to recreate the study using CFX. And there are others articles available in the Scientific Literature using CFD to solve this kind of problem...

Gert-Jan · June 12, 2019, 12:33

Probably you can use CFX as if it is a PDE-solver. You have to setup your own scalars with dispersion coefficients etc. And include the masstransfer (limitations) into the grains somehow. Don't know how, but probably possible.

If CFX is appropriate and customizable enough, I doubt it. Bottomline, CFX is a flowsolver, and in your case, the flow is the least interesting/challenging. It could be different if you would not study ions in liquid but gas adsorption where thermal effects can have a significant effect, with coupling to density and as a result to superficial velocities.

lordluan · June 12, 2019, 15:46

Quote:

Originally Posted by Gert-Jan

Probably you can use CFX as if it is a PDE-solver. You have to setup your own scalars with dispersion coefficients etc. And include the masstransfer (limitations) into the grains somehow. Don't know how, but probably possible.

If CFX is appropriate and customizable enough, I doubt it. Bottomline, CFX is a flowsolver, and in your case, the flow is the least interesting/challenging. It could be different if you would not study ions in liquid but gas adsorption where thermal effects can have a significant effect, with coupling to density and as a result to superficial velocities.

Thanks for answering. I'll take your comment into consideration. But I'll try to solve the problem with CFD...

ghorrocks · June 12, 2019, 20:58

CFX has a chemistry modelling capability so might be able to do what you are proposing. Modelling chemistry in CFD is challenging so expect that the model will take some time to develop. To get you started I would try to get some tutorial examples. Have a look at the ANSYS customer webpage and if that does not have anything suitable contact ANSYS support and ask them. They have lots of examples which are not on the web.

lordluan · June 13, 2019, 11:01

Thanks ghorrocks. I'll follow your advice.

June 11, 2019, 15:30	How to add a ionic solution and a Clay Material in ANSYS CFX?	#1
lordluan Member Lucas Join Date: May 2019 Posts: 41 Rep Power: 7	I am trying to study a system in which a solution (PbSO4+Water) flow through a porous domain (The Clay mencioned in the title), but I don't know how to add these materials. About the solution, I added the PbSO4 and Water and then created a new material treating it like a variable composition mixture (Since there will mass transfer in the study), but there wasn't any option to add the mass fractions. Do you think it's an wrong way of solving the problem? I was wondering if I can do the same with the clay.

June 11, 2019, 20:33		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,870 Rep Power: 144	How to add them depends on what you are trying to model. So what are you trying to model? What are the important physics and chemistry? __________________ Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.

June 12, 2019, 20:58		#8
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,870 Rep Power: 144	CFX has a chemistry modelling capability so might be able to do what you are proposing. Modelling chemistry in CFD is challenging so expect that the model will take some time to develop. To get you started I would try to get some tutorial examples. Have a look at the ANSYS customer webpage and if that does not have anything suitable contact ANSYS support and ask them. They have lots of examples which are not on the web. lordluan likes this. __________________ Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.

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June 11, 2019, 20:51		#3
lordluan Member Lucas Join Date: May 2019 Posts: 41 Rep Power: 7	Thanks for replying. I am trying to model the adsorption of Pb2+ in Clay. The system is a column with clay (fixed bed reactor), the solution with Pb2+ enters the column from bellow and as the solution percolates the Clay, the Pb2+ is adsorbed. I've looked the CFX tutorials but I couldn't find anything similar.

June 12, 2019, 09:23		#4
Gert-Jan Senior Member Gert-Jan Join Date: Oct 2012 Location: Europe Posts: 1,928 Rep Power: 28	My main concern is that the liquid flows through your pack bed (probably) like simple plug flow. No interesting flow phenoma occurs that justifies the use of CFD. Unless you want to model it on grain level. But I don't think so. Therefore, I always ask: "What question are you trying to answer using CFD"? The only interesting thing is the adsorption kinetics and the prediction of the breakthrough. If you want to understand the concentration profile, you'd better model that using a PDE solver (Matlab, PDESOL, or similar) dedicated for adsoprtion processes. Don't think that CFD is suitable for this. You overestimate the capabilities of CFX in this respect.

June 12, 2019, 12:33		#6
Gert-Jan Senior Member Gert-Jan Join Date: Oct 2012 Location: Europe Posts: 1,928 Rep Power: 28	Probably you can use CFX as if it is a PDE-solver. You have to setup your own scalars with dispersion coefficients etc. And include the masstransfer (limitations) into the grains somehow. Don't know how, but probably possible. If CFX is appropriate and customizable enough, I doubt it. Bottomline, CFX is a flowsolver, and in your case, the flow is the least interesting/challenging. It could be different if you would not study ions in liquid but gas adsorption where thermal effects can have a significant effect, with coupling to density and as a result to superficial velocities.

June 13, 2019, 11:01		#9
lordluan Member Lucas Join Date: May 2019 Posts: 41 Rep Power: 7	Thanks ghorrocks. I'll follow your advice.