Mass transfer

Jimmyhanchn · May 17, 2018, 02:38

Hi, I am Jimmy. I would like to make a simulation for membrane separations. Concentration near the membrane surface should be cleared. I have read many papers about this. CFX as a powerful tool was used in their simulation. But I still can not understand some basic methods. Give me some suggestions or tips in your similar simulation or answer two question.
1)How to input partial differential equations like listed in fig?

2)What is the difference between inlet boundary and source?
Thank you very much!

ghorrocks · May 17, 2018, 19:08

1) Look in the CFX Reference manual, the section on CEL variables. You will find you can calculate gradients and other functions of variables which should allow you to enter the equation you show.
2) An inlet boundary is a boundary which has been defined as an inlet. It does not change the equations, just applies the boundary condition. A source term is a change to the equations where a source term is added. Source terms are very flexible and can be made to do all sorts of things, but you will need to work out the mathematics of how to do it.

Jimmyhanchn · May 21, 2018, 01:50

Thank you very much for your reply, but unfortunately, I still can not understand your explanation. Can you me some materials example or book? I really need to know how to realize them in details. For example, what the different of source setting and inlet setting, and how to set mass source?

Jimmyhanchn · May 21, 2018, 02:10

I think I found the book you mentioned, but I havent found the section about gradient function. I will try, thank you for your kindness.

Quote:

Originally Posted by ghorrocks

1) Look in the CFX Reference manual, the section on CEL variables. You will find you can calculate gradients and other functions of variables which should allow you to enter the equation you show.
2) An inlet boundary is a boundary which has been defined as an inlet. It does not change the equations, just applies the boundary condition. A source term is a change to the equations where a source term is added. Source terms are very flexible and can be made to do all sorts of things, but you will need to work out the mathematics of how to do it.

ghorrocks · May 21, 2018, 06:22

Look in the section on CEL variables, as I said previously.

Jimmyhanchn · May 26, 2018, 02:30

I have read the part of the manual, but I still can not understand how to input concentration gradient and the equation. The part you mentioned is '14. CFX Expression Language(CEL)' or '16.Variables in ANSYS CFX', there is no information about partial derivative and gradient. I have tried to search for these keywords in the whole manual, I got nothing. Help me, please, I really need your suggestion.

Quote:

Originally Posted by ghorrocks

Look in the section on CEL variables, as I said previously.

ghorrocks · May 26, 2018, 03:58

See: https://www.sharcnet.ca/Software/Ans.../i1305073.html

<Concentration variable name>.grad x

Jimmyhanchn · May 27, 2018, 01:20

Thank you very very much! I will try.

Quote:

Originally Posted by ghorrocks

See: https://www.sharcnet.ca/Software/Ans.../i1305073.html

<Concentration variable name>.grad x

May 17, 2018, 19:08		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	1) Look in the CFX Reference manual, the section on CEL variables. You will find you can calculate gradients and other functions of variables which should allow you to enter the equation you show. 2) An inlet boundary is a boundary which has been defined as an inlet. It does not change the equations, just applies the boundary condition. A source term is a change to the equations where a source term is added. Source terms are very flexible and can be made to do all sorts of things, but you will need to work out the mathematics of how to do it. __________________ Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.

May 21, 2018, 06:22		#5
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	Look in the section on CEL variables, as I said previously. __________________ Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.

May 26, 2018, 03:58		#7
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	See: https://www.sharcnet.ca/Software/Ans.../i1305073.html <Concentration variable name>.grad x Jimmyhanchn likes this. __________________ Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
mass transfer coefficient	ArturTU	FLUENT	1	October 27, 2015 10:04
Question about heat transfer coefficient setting for CFX	Anna Tian	CFX	1	June 16, 2013 06:28
About phase change heat and mass transfer	Michael	FLUENT	2	February 13, 2011 01:49
How to calculate Volumetric Mass transfer coefficient using CFX?	tuks_123	CFX	2	July 22, 2010 01:15
Vof, udf and mass transfer panel	Jay	FLUENT	1	March 15, 2005 00:29

May 21, 2018, 01:50		#3
Jimmyhanchn Member Jimmy Join Date: Sep 2016 Location: Japan Posts: 38 Rep Power: 9	Thank you very much for your reply, but unfortunately, I still can not understand your explanation. Can you me some materials example or book? I really need to know how to realize them in details. For example, what the different of source setting and inlet setting, and how to set mass source?