×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Help with Transient Thermal Analysis

Help with Transient Thermal Analysis

Help with Transient Thermal Analysis

(OP)
Hello,

I am using Simulation for a transient thermal analysis for the first time.

To start I am simply modeling a solid copper rod with a heat load attached at the end. The heat load (watts) varies as a function of temperature. The heat load is actually a cooling curve taken from one of our cryogenic cold-heads.

The question I have I believe is pretty basic but I am unable to figure out what I am doing wrong here.

I have applied an initial condition to all faces of the rod and set them to 293 Kelvin. My total time (just to start) is 100 s with 10 s intervals.

The part meshes and I am able to run the analysis. The results are not believable. The rod cools much, much to fast. At first I thought I may have the cooling curve improperly set up or possibly the material properties. So far I do not believe that is the problem.

I went ahead and suppressed the heat load altogether. The part should then sit at 293 K indefinetly. After running the analysis again I find out that it does not. After only a few seconds the part cools itself down to ~5 K.

Is there something in the initial conditions I am not setting up properly? I see that I am able to select faces, but really I need the entire volume to be set to the initial temperature. Is this the problem? Is the problem that I am not setting the entire mesh to the initial temperature? How do I do that?

Thanks,
  Dan  

RE: Help with Transient Thermal Analysis

I suspect that the inernal nodes are initially set at 0 K with the nodes on the outer face at 293 K. With your large time step I'd imagine that the results would not be stable over the transient and that temperatures would oscillate as temperatures tried to balance between 293 and 0 K, and hence go negative. Use a smaller time step in your original analysis.  

corus

RE: Help with Transient Thermal Analysis

(OP)
Thanks Corus,

How do I set the internal node temperatures? I seem to only be able to select faces when I set up the initial conditions.

 

RE: Help with Transient Thermal Analysis

(OP)
EDIT: I had to create an assembly and insert my single part. This allowed me to select entire components and not just faces/edges.

Problem solved, on to next problem.

Thanks

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources