 ## General Mechanical

• dario.guarino
Subscriber

Hello,

I am solving a transient thermal problem.

I would like to use the calculated temperature of certain node o surface, at a timestep N, as input for the step N+1. I want to compare the temperature at timestep N with a certain reference temperature at timestep N+1.

In function of the outcome ( T(N) bigger or smaller wrt the reference) I want to use a certain coefficient at timestep N+1 instead of another.

Is it possible to do such a thing? maybe via APDL or python script?

Thank you

Regards

• Sheldon Imaoka
Ansys Employee

Sorry that I don't quite understand your question, but are you trying to define temperature-dependent film coefficients? If so, this can be directly done via the "Convection" object.
If this is not the case, can you clarify what is meant by "certain coefficient at timestep N+1"? What coefficient are you referencing?
Generally speaking, you can have temperature-dependent material properties or temperature-dependent thermal loads and boundary conditions. Ansys Mechanical does not evaluate the temperature-dependency based on the previous timestep - instead, Newton-Raphson method is used to iterate to ensure that the temperature-dependency is evaluated at the current temperature. This is more accurate than using the previous temperature for the current timestep (if you evaluated based on temperature of previous timestep, then accuracy would be dependent on timestep size).
Regards Sheldon

• dario.guarino
Subscriber

Thank you for your answer. Indeed my message was not really clear, I will try to reformulate.
With a transient thermal I am simulating a steam flow that invests a surface. The surface is initially cold.
I have prepared an excel file, that I use as input to define the convection coefficient and the ambient temperature, that change over time. Those values have been pre-defined via a script external to Ansys and condensation is not taken into account. Now I would like to improve my model by considering the condensation phenomenon.
Initially I expect condensation, since my surface is going to be colder than the saturation temperature. As the time passes, my surface will warm and become hotter than the saturation temperature. At this point there will not be condensation anymore.
I would like to do that by checking each step the temperature of my surface and compare it to the saturation temperature, that needs to be calculated each step.
I am trying to find out how this can be done. The temperature of my surface at step N, should be used at timestep N+1 to be compared with the saturation temperature (calculated at timestep N+1).
In function of the outcome of the check, a certain convection coefficient will be used. (coefficient X if T < Tsat and coefficient Y if T >Tsat).
I hope it is a bit more clear
Thank you again!
Kind regards

• Sheldon Imaoka
Ansys Employee 