## General Mechanical

#### Temperature rise over a surface

• cfd_learner
Subscriber

Dear,

I would like to find the time of temperature rise over surface 100mm away from a heating rod having a constant temperature of 100 degC.

1. What should be the BCs (for the surface where temperature rise will be computed and surrounding environment)?
2. How to set time step in the simulation?
3. Simulation will be steady or transient thermal?
4. Do I simulate this in Ansys Mechanical or Ansys Fluent?
5. The air is assumed static around the heating rod.

See the problem definition in the picture attached.

Regards.

• Karthik R
Administrator
Hello,nThe modeling approach depends on your end goal.nIf you don't want to worry about the air in the middle (only radiation) - you should be able to use either Fluent or Mechanical. Both tools are capable of handling radiation (and conduction) heat transfer.nIf you wish to include the motion of air (in the enclosure) due to natural convection (in reality, air is not going to be static), then you should be solving the NS equations in air. This becomes a conjugate heat transfer problem and you will need to solve this in Fluent. nAs a first crack, you could solve just the radiation (+ conduction) heat transfer. In this case, you will need to make some assumptions about the magnitude of heat transfer coefficients on the air side. You could use a constant wall temperature T = 100 degC at the heated rod wall. On the surface side, you could provide a convection heat transfer (h and T_amb) and a corresponding radiation condition (emissivity and so on). You might want to include the enclosure in your analysis as the rod would radiate heat is multiple directions. Also, because you are interested in temperature rise as a function of time, you should be running a transient analysis. nIf you have not already looked into this video, I'd strongly recommend that you watch it. It should help you understand how to set-up this problem in Ansys Transient Thermal.nI hope this answers all your questions.nThank you.nKarthikn
• cfd_learner
Subscriber
Thank you.nThe measuring surface actually in air.nIt is just like feeling temperature above a room heater (electric).nThe BCs you told will remain similar in this condition?nI think Conjugate heat transfer approach is feasible in this case.RegardsnAlin
• Karthik R
Administrator
Excellent. Please feel free to use Fluent. There are several tutorials on how to set-up natural convection and radiation problems in Fluent. Here is a YouTube video on setting up Natural Convection in Fluent.nIf you wish to try this example at your end, please look for the files as well as a detailed explanation of the results in our free Ansys Innovation Courses (AICs). Here is the link.nI hope this helps you get started.nThanks.nKarthik
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