create a mixture of water and calcium carbonate CaCO3

othach · April 6, 2020, 11:05

Hi,
it's my first time with CFX, I want to incorporate a mixture of water and calcium carbonate, but I don't know how.
Can you help me
thank you

Gert-Jan · April 6, 2020, 13:42

Is CaCO3 dissolved? Slurry? Rocks?
In other words: what is the goal of your simulation?

othach · April 7, 2020, 11:44

The purpose of the simulation is the crystallization of calcium carbonate particles on the surface of a heat exchanger so the incoming water must contain CaCO3.

Gert-Jan · April 7, 2020, 12:01

So, you have water with dissolved CaCO3. And precipitation/cristalisation occurs on the tubes because of lower solubility? And you don't want to solve the CaCO3 particles?

Then you can define an additional variable that represents the CaCO3 concentration. Include a negative source term on the tubes to include the crystallisation of the CaCO3. This way you will get a concentration profile.

This is possible if you can ignore density differences due to the concentration variations and can ignore the particles.

othach · April 10, 2020, 15:22

I added the calcium carbonate because I couldn't find it in the database library, then I created a mixture of water and CaCO3.
but I don't know how to add the solidification equations to have a crystallization of CaCO3 on the surface of the tubes.
Thanks for your help.

ghorrocks · April 10, 2020, 20:50

Solidifcation is not a simple process. It is a nucleation process, so is very complex physics. There is no such thing as a "solidification equation" you turn on. Nucleation processes are challenging to model for CFD experts so definitely not something a beginner should attempt.

Can you describe what you are trying to and what you want to learn? We might be able to help you with a simulation which will be possible to complete.

othach · April 11, 2020, 13:51

I want to study the phenomenon of fouling due to CaCO3 crystallization on a cross-flow heat exchanger. I have cold water with calcium carbonate at the inlet and a tube containing hot water on which the CaCO3 particles must accumulate.
But I don't know how to integrate these equations that will allow me to study fouling.

ghorrocks · April 11, 2020, 21:25

There are no built in equations in CFX to do this. You are going to have to develop this model yourself - and this is a complex and difficult task and would take an experienced CFD practitioner several months of development work to get running. If you are a CFD beginner you have no hope of successfully completing this model.

Are you sure the model you propose is realistic? Maybe you should consider simplifying it to something which can be done in a realistic time frame?

othach · April 12, 2020, 10:03

Do you have any suggestions that will allow me to simplify the model in order to achieve it in a realistic timeframe?

Thank you for your help

ghorrocks · April 12, 2020, 18:18

That depends on what you are trying to achieve. Why are you doing this analysis? What are you hoping to learn? What are you going to do based on the results of this analysis?

othach · April 18, 2020, 15:25

The objective of this analysis is to study the effect of fouling build-up on the tubes of a heat exchanger.
So I have to create a simplified model that will allow me to predict this fouling.

ghorrocks · April 19, 2020, 00:04

You have to be really careful here so that you know what you are actually doing. Your two sentences are contradictory - you say you are studying the effect of fouling build up on the tubes. You would model this by solid modelling the fouling build up on the pipes and doing a simulation of the pressure loss and other factors of that. This model does not require any modelling of the CaCO3 crystallisation process. But then your second sentence states you need to create a model of the fouling process, despite your first sentence implying it is not required.

So what are you actually trying to model? If you want the effect of the fouling you don't need to model the fouling process, just the end result of the fouling build up on the tube.

othach · May 1, 2020, 17:35

I need to create a model of the fouling process in order to predict the fouling build-up on the heat exchanger tubes.

April 6, 2020, 11:05	create a mixture of water and calcium carbonate CaCO3	#1
othach New Member othman acheh Join Date: Apr 2020 Posts: 7 Rep Power: 6	Hi, it's my first time with CFX, I want to incorporate a mixture of water and calcium carbonate, but I don't know how. Can you help me thank you

April 10, 2020, 20:50		#6
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	Solidifcation is not a simple process. It is a nucleation process, so is very complex physics. There is no such thing as a "solidification equation" you turn on. Nucleation processes are challenging to model for CFD experts so definitely not something a beginner should attempt. Can you describe what you are trying to and what you want to learn? We might be able to help you with a simulation which will be possible to complete. __________________ Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.

April 11, 2020, 21:25		#8
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	There are no built in equations in CFX to do this. You are going to have to develop this model yourself - and this is a complex and difficult task and would take an experienced CFD practitioner several months of development work to get running. If you are a CFD beginner you have no hope of successfully completing this model. Are you sure the model you propose is realistic? Maybe you should consider simplifying it to something which can be done in a realistic time frame? __________________ Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.

April 12, 2020, 18:18		#10
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	That depends on what you are trying to achieve. Why are you doing this analysis? What are you hoping to learn? What are you going to do based on the results of this analysis? __________________ Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.

April 19, 2020, 00:04		#12
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	You have to be really careful here so that you know what you are actually doing. Your two sentences are contradictory - you say you are studying the effect of fouling build up on the tubes. You would model this by solid modelling the fouling build up on the pipes and doing a simulation of the pressure loss and other factors of that. This model does not require any modelling of the CaCO3 crystallisation process. But then your second sentence states you need to create a model of the fouling process, despite your first sentence implying it is not required. So what are you actually trying to model? If you want the effect of the fouling you don't need to model the fouling process, just the end result of the fouling build up on the tube. __________________ Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.

April 6, 2020, 13:42		#2
Gert-Jan Senior Member Gert-Jan Join Date: Oct 2012 Location: Europe Posts: 1,827 Rep Power: 27	Is CaCO3 dissolved? Slurry? Rocks? In other words: what is the goal of your simulation?

April 7, 2020, 11:44		#3
othach New Member othman acheh Join Date: Apr 2020 Posts: 7 Rep Power: 6	The purpose of the simulation is the crystallization of calcium carbonate particles on the surface of a heat exchanger so the incoming water must contain CaCO3.

April 7, 2020, 12:01		#4
Gert-Jan Senior Member Gert-Jan Join Date: Oct 2012 Location: Europe Posts: 1,827 Rep Power: 27	So, you have water with dissolved CaCO3. And precipitation/cristalisation occurs on the tubes because of lower solubility? And you don't want to solve the CaCO3 particles? Then you can define an additional variable that represents the CaCO3 concentration. Include a negative source term on the tubes to include the crystallisation of the CaCO3. This way you will get a concentration profile. This is possible if you can ignore density differences due to the concentration variations and can ignore the particles.

April 10, 2020, 15:22		#5
othach New Member othman acheh Join Date: Apr 2020 Posts: 7 Rep Power: 6	I added the calcium carbonate because I couldn't find it in the database library, then I created a mixture of water and CaCO3. but I don't know how to add the solidification equations to have a crystallization of CaCO3 on the surface of the tubes. Thanks for your help.

April 11, 2020, 13:51		#7
othach New Member othman acheh Join Date: Apr 2020 Posts: 7 Rep Power: 6	I want to study the phenomenon of fouling due to CaCO3 crystallization on a cross-flow heat exchanger. I have cold water with calcium carbonate at the inlet and a tube containing hot water on which the CaCO3 particles must accumulate. But I don't know how to integrate these equations that will allow me to study fouling.

April 12, 2020, 10:03		#9
othach New Member othman acheh Join Date: Apr 2020 Posts: 7 Rep Power: 6	Do you have any suggestions that will allow me to simplify the model in order to achieve it in a realistic timeframe? Thank you for your help

April 18, 2020, 15:25		#11
othach New Member othman acheh Join Date: Apr 2020 Posts: 7 Rep Power: 6	The objective of this analysis is to study the effect of fouling build-up on the tubes of a heat exchanger. So I have to create a simplified model that will allow me to predict this fouling.

May 1, 2020, 17:35		#13
othach New Member othman acheh Join Date: Apr 2020 Posts: 7 Rep Power: 6	I need to create a model of the fouling process in order to predict the fouling build-up on the heat exchanger tubes.