Heat transfer problem

jerometeoh
jerometeoh Altair Community Member
edited April 2023 in Community Q&A

Good afternoon, I have a question need some heat transfer experts help me to answer.

It is related to the heat convection coefficient.

For example, I have an object (blue)  as shown in the picture below that I have been defining its boundary conditions, including heat convection coefficient of 12.5.

And now I have it in contact with another object (orange). Can I still define the rest of the expose surface as 12.5?

If not, how do I calculate this difference or another value for it?

Do we have a way to characterize heat transfer coefficient for modeling?

Last one, is the value of heat transfer coefficient depending on the object? I mean object in orange, can I defind its as 12.5 on the boundary as well?

 

Thank you so much!

Jerome.

image

 

 

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Answers

  • Payal Pawar_20288
    Payal Pawar_20288
    Altair Employee
    edited April 2023

    Hi,

    Can you let me know which Altair product are you using so that I can direct your question to the proper forum?

  • jerometeoh
    jerometeoh Altair Community Member
    edited April 2023

    Thanks Payal.

    I am using the Flux and Hyperworks.

     

  • Farid zidat_20516
    Farid zidat_20516
    Altair Employee
    edited April 2023

    Hello Jerome;

    As you know in Flux those coefficients are inputs!

     

    From my point of view, if the bodies are in contact, so there will be thermal conduction, and remaining faces / lines will be defined with convection!

     

    Since i am not really an expert in this domain i added your request to the AcuSolve, and Hyperworks CFD group, so you may have more chance to get an answer from experts.

     

    Regards

  • Jagan Adithya Elango
    Jagan Adithya Elango Altair Community Member
    edited April 2023

    You can specify convective coefficient to the exposed faces with appropriate reference temperature.

    image

    If both the orange and blue objects are exposed to same ambient conditions you could use the same convective coefficient value.

    Did you analytically find out the convective coefficient using non dimensional numbers? if so, you could do that with the orange object too. Or else you could run a natural convection simulation in cfd and calculate the value.

  • jerometeoh
    jerometeoh Altair Community Member
    edited April 2023

    Thanks Jadan.

     

    I am not sure how to find out the convective coefficient using a non dimensional numbers, if fact, do you have any example?

    I am parametrically change the value and see which one match up at the momet which is very time consuming.

     

    Thanks,

    Jerome.

  • Jagan Adithya Elango
    Jagan Adithya Elango Altair Community Member
    edited April 2023 Answer ✓
    Jerome Teoh said:

    Thanks Jadan.

     

    I am not sure how to find out the convective coefficient using a non dimensional numbers, if fact, do you have any example?

    I am parametrically change the value and see which one match up at the momet which is very time consuming.

     

    Thanks,

    Jerome.

    How did u arrive to the value of 12.7 W/mK and is this a forced or natural convection?

    You could refer the following to analytically determine heat transfer coefficient but the most preferred and accurate way is to run a CFD simulation.

    Forced Convection:
    https://www.engineeringexcelspreadsheets.com/2011/03/forced-convection-heat-transfer-coefficient-calculator/

    Natural Convection:
    https://www.engineeringexcelspreadsheets.com/2011/05/natural-convection-heat-transfer-coefficient-calculator/

  • jerometeoh
    jerometeoh Altair Community Member
    edited April 2023

    Jagan. Thanks. This is a natural convection.

    I kind of just adopted the range from an online source and run parametric sweep simulation to match the cooling curve.

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