Learning Forum

[Raheem Shaik (IIT KGP)]

Hi all.

I am facing floating point exception error. I have tried so many ways to get rid of it. But still I am not able to resolve the issue. I am doing a 2d simulation of the domain having porous media in which refrigerant flows. R134a refrigerant is given as real gas nist. Boundary conditions are as follows bottom and left side walls as isothermal walls (at 308 K) Right side is symmetry top is considered as adiabatic wall. Domain initial pressure is 11.5bar and temp is 351K . It has to cool to 308K I am using udf to add mass and energy source terms. error showing divergence detected in AMG solver. I couldn't sort out this error. I have set the verbosity in controls settings as 1. Then it was showing temp, pressure equations tolerance. There I have found that the temperature equation has high tolerance (1.643 e+3). It was showing "" Exit as omega becomes NaN for a norm of s equals to 0.0000e+00 "". I have no idea what it is and how to control it. I am attaching the error message here. Please guide me to solve the issue.

 

[Rob]

What is the UDF for? Ie what's it doing that's not covered in the rest of the solver?

[Raheem Shaik (IIT KGP)]

Udf is to add mass and energy source terms to the default conservation equations. My simulation is related to adsorption refrigeration.

[Rob]

If you monitor the energy & mass in the source terms are they still sensible? 

[Raheem Shaik (IIT KGP)]

Actually I did the same simulation with other refrigerant( ethanol ). That worked fine. UDF also correct only.I checked the temp and pressure values just before error occurs, everything looks normal. No sudden change in the values. I am not able to get the reason for the error.  I have put the energy eqn off for some time and run the simulation. When I am keeping energy eqn on, agian i am getting the same error after 1.3 sec of simulation.

[Rob]

How close are you to any abrupt property changes with the refrigerant?