[TallesC]

Hello,

I'm working with 31 cracking reactions of 1,2-dichloroethane system involving radical and molecular species.

In the term rate of reactions x enthalpy, the energy balance of the one-dimensional model reactor that term appears as the minus sign (-). My doubt is the insertion of generation or power consumption term should be entered with a negative value with source term in CFX?

the model of reaction rates follows the arrenhius.

enthalpy of reaction = enthalpy of formation of reaction(const) + Cp(const) (T-298.15)

thank you!

[Opaque]

It would be great if you describe your mathematical problem in more detail.

From your description of the source term, it seems you may need to read the ANSYS CFX documentation for the energy transport equation in detail. There are no source terms for chemical reactions, and they are not needed because how the material properties and mixture definitions are setup.

Your approach seems to be based on splitting the definition of static enthalpy as the sum of enthalpy of formation plus integral of Cp over the temperature range. Then, substituting such definition into the energy transport equation and the final form should contain a source term similar to what you described.

[TallesC]

So I'm tried to implement the reaction kinetics of EDC cracking who had spoken in a pipe 365 m approximately (the reactor), to simplify am using a slice of 4 degrees and symmetry condition. the surface is specified a coefficient of thermal change as a function of reactor temperature and external temperature is fixed. fluid enters the temperature of 250 degrees Celsius is expected that the temperature rises along the pipe so that the cracking from happening. when I put the term source of energy as a negative that I monitor the temperature drops in the output, which is not going to happen when I leave the positive term temperature rises as expected but interaction 25, the following problem occurs:

Newton's method warnings at: END OF TIME STEP |
+--------------------------------------------------------------------+

+--------------------------------------------------------------------+
| |
| Newton's method failed to converge while computing the variables |
| listed below. In each case, the solver continued with the variable |
| field as it was on the final iteration. |
| |
| If this situation persists, you might try decreasing the Newton |
| iteration underrelaxation factor. This can be changed by setting |
| one of the following parameters for your mixture: |
| |
| Temperature : "Constitutive Relation Under Relaxation" |
| Pressure : "Newton Pressure Under Relaxation" |
| |
+--------------------------------------------------------------------+
| |
| Location Name : serpentina |
| Mesh location : VERTICES |
| Routine : UPD_LOCALE_PROP1 |
| Partition : 10 |
| Variable Name : Temperature |
| Last 3 Changes : 5.18607E+35 5.18607E+35 5.18607E+35 |
| Tolerance : 1.0000E-02 |
| Status : STALLED |
| Max Iterations : 100 |
| |
+--------------------------------------------------------------------+

================================================== ====================
OUTER LOOP ITERATION = 28 CPU SECONDS = 5.302E+03
----------------------------------------------------------------------
| Equation | Rate | RMS Res | Max Res | Linear Solution |
+----------------------+------+---------+---------+------------------+

Parallel run: Received message from slave
-----------------------------------------
Slave partition : 2
Slave routine : ErrAction
Master location : Message Handler
Message label : 001100279
Message follows below - :

+--------------------------------------------------------------------+
| ERROR #001100279 has occurred in subroutine ErrAction. |
| Message: |
| Floating point exception: Overflow |
| |
| |
| |
| |
| |
+--------------------------------------------------------------------+

Parallel run: Received message from slave
-----------------------------------------
Slave partition : 2
Slave routine : ErrAction
Master location : Message Handler
Message label : 001100279
Message follows below - :

+--------------------------------------------------------------------+
| ERROR #001100279 has occurred in subroutine ErrAction. |
| Message: |
| Stopped in routine FPX: C_FPX_HANDLER |
| |
| |
| |
| |
| |
+--------------------------------------------------------------------+

+--------------------------------------------------------------------+
| ERROR #001100279 has occurred in subroutine MESG_RETRIEVE. |
| Message: |
| Stopping the run due to error(s) reported above |
| |
| |
| |
| |
| |
+--------------------------------------------------------------------+

+--------------------------------------------------------------------+
| An error has occurred in cfx5solve: |
| |
| The ANSYS CFX solver exited with return code 1. No results file |
| has been created. |
+--------------------------------------------------------------------+

End of solution stage.

+--------------------------------------------------------------------+
| The following user files have been saved in the directory |
| C:\2D_Full_reaction\CFX6_001: |
| |
| pids, mon |
+--------------------------------------------------------------------+


This run of the ANSYS CFX Solver has finished.

[Opaque]

Not sure how you setup the materials, nor the reactions.

Based on the ANSYS CFX theory, I do not understand why you are adding a source term at all into the energy equation.

[TallesC]

to represent that there is a source of energy due to reaction of power generation as well as mass generation due to chemical reactions.

[Opaque]

There is a tutorial about a can combustor using different reactions mechanism, and if you follow them you will see there are no source terms required in the energy equation, nor source terms in the species equation.

If the reaction is at surface only, and you need to modeled manually (ANSYS CFX does not include surface reactions), then I can see the need for a energy source.