## General Mechanical

#### Forced Convection in Transient Thermal

• UzairAhmed
Subscriber

hello all!

I've recently been trying to simulate the temperature rise in a thick-walled cylinder, which has a heat flux into its inner wall and convection on its outer surface. while natural convection is possible through the convection samples, there are no options for convection due to moving air. Is there any way to set the film coefficient according to velocity of moving air? Please note that I am using Transient Thermal because I only care about the temperature of the cylinder, not of the outside air.

Regards,
Uzair Ahmed

• peteroznewman
Subscriber

Here is a good reference.

The last example shows the calculation of a film transfer coefficient, h, which is a function of Nusselt number, which is a function of Reynolds number, which is a function of velocity.

• UzairAhmed
Subscriber

thank you for the input
However, these calculations are for flat plates and cylinders in cross-flow. However, I do have a general direction

Thank you

• PSiedlac123
Subscriber

Yes You can create very complex convection boundary conditions based on multiple variables by using build in interpolation in APLD tables, but first You need to know the values to put in the table, so equation is needed, what in general case can lead to CFD.

Despite convection model itself did You consider FLUID116. It can simplify Your model by adding temperature distribution of fluid along flow axis.

Hope this helps a little.

• UzairAhmed
Subscriber

Thank you for the input!
I did consider FLUENT, but since the model would have to be made considerably more complex in order to accommodate the two fluids (both inside and outside the cylinder), and I am not looking into the behavior of the fluids, I decided to go with transient thermal.
I have not studied APDL, but ill try it.
Thank you!