# Temperature rise over a surface

Member

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.

Hello,

The modeling approach depends on your end goal.

1. If 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.
2. If 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.

As 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.

If 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.

Thank you.

Karthik

• Member

Thank you @Kremella.

The measuring surface actually in air.

It is just like feeling temperature above a room heater (electric).

The BCs you told will remain similar in this condition?

I think Conjugate heat transfer approach is feasible in this case.

Regards

Ali