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How to couple interface "Transport of Diluted Species" with interface "Surface Reactions"?
Posted Feb 18, 2014, 9:19 a.m. EST Chemical Reaction Engineering Version 4.3b, Version 5.1 3 Replies
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Hi, I'm trying modify the sample "Chemical Vapor Deposition of GaAs" in modle library. The sample simulates reaction flow in a given space but only solve concentration in flow. Simulation of deposition on a given surface is absent, though this sample already includes all surface reactions needed in "Reaction Engineering" interface in Modle 1.
I try to add a "Surface Reactions" interface to the modle, and add 8 surface species reactions rate fields and one bulk species reaction field accord to species settings in "Reaction Engineering". I fill them with variables whose form like variables settings in reaction node of "Transport of Diluted Species".
Finally I recompute study but failed. Message box show there exist void equations for the variables I just add. Error message look like this:
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Failed to find a solution.
Singular matrix.
There are 309 void equations (empty rows in matrix) for the variable mod2.cb1.
at coordinates: (-0.2,-0.05), (-0.198707,-0.05), (-0.197408,-0.05), (-0.196109,-0.05), (-0.19481,-0.05), ...
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could anyone know how to get rid of this problem? thanks.
I try to add a "Surface Reactions" interface to the modle, and add 8 surface species reactions rate fields and one bulk species reaction field accord to species settings in "Reaction Engineering". I fill them with variables whose form like variables settings in reaction node of "Transport of Diluted Species".
Finally I recompute study but failed. Message box show there exist void equations for the variables I just add. Error message look like this:
--------------------------------------------------------------------------------------------------------------------
Failed to find a solution.
Singular matrix.
There are 309 void equations (empty rows in matrix) for the variable mod2.cb1.
at coordinates: (-0.2,-0.05), (-0.198707,-0.05), (-0.197408,-0.05), (-0.196109,-0.05), (-0.19481,-0.05), ...
--------------------------------------------------------------------------------------------------------------------
could anyone know how to get rid of this problem? thanks.
3 Replies Last Post Jun 25, 2015, 4:38 a.m. EDT
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Posted:
1 decade ago
I spent another serveral hours on this sample, and I am confused by a problem that how COMSOL identify a species is gas species or surface species? Obviously they have diffrent attributes and behavior.
COMSOL has defined gas reactions and surface reactions, and species in a gas reaction are gas species of course, but in a surface reaction a species could be a gas species or could be a surface species! It seems that COMSOL couldn't distinguish them! In fact, in this sample units of surface species concentration are mol/m^3 which is ientical with gas species concentration, but I think they should be mol/m^2. As a result, rate of surface reactions should be mol/(m^2-s), not mol/(m^3-s). This is why reaction rate field of the third surface reaction "SAgahet=>gahet" prompts error with orange color.
Could anyone tell me my conclusion is true or false? Thanks.
COMSOL has defined gas reactions and surface reactions, and species in a gas reaction are gas species of course, but in a surface reaction a species could be a gas species or could be a surface species! It seems that COMSOL couldn't distinguish them! In fact, in this sample units of surface species concentration are mol/m^3 which is ientical with gas species concentration, but I think they should be mol/m^2. As a result, rate of surface reactions should be mol/(m^2-s), not mol/(m^3-s). This is why reaction rate field of the third surface reaction "SAgahet=>gahet" prompts error with orange color.
Could anyone tell me my conclusion is true or false? Thanks.
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Posted:
10 years ago
Excuse me , did you solve this problem about surface reaction?
I am sure that COMSOL can not judge whether the species reaction is gas reaction or surface reaction, but is there any button can be really used for reaction from gas to solid like MOCVD? Is the "surface reaction"interface suitable ? because only the "surface reaction"can select the boundary as a surface , than we can choose the surface concentration , but i don't know my opinion is right or not ,can u answer me ?
hope for your reply ,thank you
I am sure that COMSOL can not judge whether the species reaction is gas reaction or surface reaction, but is there any button can be really used for reaction from gas to solid like MOCVD? Is the "surface reaction"interface suitable ? because only the "surface reaction"can select the boundary as a surface , than we can choose the surface concentration , but i don't know my opinion is right or not ,can u answer me ?
hope for your reply ,thank you
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Posted:
9 years ago
I tried with the model downloaded with v5.0 and it would not solve Study 2 (within several hours). Then I upgraded to v5.1 and the Study 2 model solved within 2 min. As you say it shows nothing about the thickness of the deposited layer, which is surely the main interest.
In terms of defining what is a gas species and what is a surface species it looks to me that the CHEMKIN parameters file uses an (s) after the species name to denote surface species. According to the pdf instructions the variables become name_surf, but I think they became name_(ads). But maybe this is a change in v5.1 and doesn't apply for the 4.3b of the OP. ??
In terms of defining what is a gas species and what is a surface species it looks to me that the CHEMKIN parameters file uses an (s) after the species name to denote surface species. According to the pdf instructions the variables become name_surf, but I think they became name_(ads). But maybe this is a change in v5.1 and doesn't apply for the 4.3b of the OP. ??