×
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

Conditional enthalpy properties Workbench

Conditional enthalpy properties Workbench

Conditional enthalpy properties Workbench

(OP)
Could you please give a hint how to apply conditional enthalpy properties depending on thermal loads?
For example I have a material with different enthalpy properties for cooling and heating processes.
How can I specify that during cooling one values must be applied and during heating
the other ones.

Initially I apply the temperature dependent enthalpy values in Engineering Data in Workbench (ANSYS 15.0) and then time dependent heat flux. To specifiy values during cooling when heat flux is equal to zero I use a command line in my transient thermal model and I write like this

*IF,_load(4,1,1),EQ,'0',THEN
mptemp,1,0,26,27,28,29,100 ! for temperatures 26,27...30
mpdata, enth, matid, 1, 0, 100,150,200,250,500 ! enthalpy values 100,150..300
*ENDIF

Obviously it is not working. Looking forward to hear some suggestions! Thank you.

RE: Conditional enthalpy properties Workbench

AliceEng,

Could you explain in detail what is meant by "different enthalpy properties for cooling and heating processes" of this material. I was taught that enthalpy was a state function and path independent.

Good luck,
Latexman

Technically, the glass is always full - 1/2 air and 1/2 water.

RE: Conditional enthalpy properties Workbench

The best thing for you to understand enthalpy is to go on line and check this particular topic under thermodynamics. You should not expect us to teach you enthalpy in few sentences when thermodynamics is covered in college during a quarter.

RE: Conditional enthalpy properties Workbench

(OP)
Dear Latexman, thank you for you reply. I have attached the data sheet of the material that I use. If you look at the partial Enthalpy Distribution you may find red and blue indicators for heat and cool. This material is able to store heat, moreover for some of the materials from this series the melting and congealing temperature range can also differ. I hope I have answered on your question.

Dear chicopee, I do not expext from you to teach me. If you see that someone´s question is wrong why do you even spend your time answering on it at all...

RE: Conditional enthalpy properties Workbench

I agree with Chicopee

RE: Conditional enthalpy properties Workbench

Great post Randy as usual

RE: Conditional enthalpy properties Workbench

AliceEng,

I do not use Workbench (ANSYS 15.0), so I cannot help with your approach and code you provided. My advice is to educate yourself thoroughly on the physical and thermodynamic behavior of these compounds. Research and buy the best book on the subject. Buy some pertinent cutting edge journal articles. Ask the supplier's technical expert (yes, call them up and ask to speak to their expert) how they model the fluid. The brochure says it is a pure PCM. I wonder if the fluid is a pure single component, or a mixture of components. The fluids behavior makes sense to me if it is a mixture of similar compounds, maybe isomers or just different molecular weights. One of the first questions you need to answer is, how sophistocated does your model have to be to be close enough. Can you model it as a pure component with a melting point of 35oC? It'll only be off +/- 1-2oC. In my opinion, that's pretty close. Maybe in your application, it's not. In that case, model it as a mixture of similar compounds that have a range of pure component melting points between 33 and 37oC. Call Workbench and ask their technical support how to medel the fluid.

Good luck,
Latexman

Technically, the glass is always full - 1/2 air and 1/2 water.

RE: Conditional enthalpy properties Workbench

(OP)
Thank you very much for the replies.

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