[hackis20]

Hello everyone, i am analyzing the heat transfer for plate air cooling.

I made geometry and mesh using gambit and read the mesh in fluent.

The thermal boundary condition for wall(plate and shadow) is coupled that i found the coupled condition from the tutorial, also other posts in CFD Forum.

After calculation, heat transfer was happened sucessfully but, i want to define the heat transfer coefficient(h) along the surface temperature of plate.

As you know coefficient(h) is different depends on the surface temperature.
However, there in no option to input the value of coefficient anywhere.

Please give me some advice to solve this problem. thanks

[NickFL]

Gambit? Wow, that is a flash from past. Is ANSYS even supporting that anymore?



For your problem you have an initial temperature of the plate. The plate is then cooled with cold air blowing over it, correct? I think there is a misunderstanding going on here. Fluent calculates the energy equation where the heat transfer coefficient is a post-processing quantity (that is a result of the solution). This means that you cannot specify h with the coupled thermal conditions. If you had a plate where you knew the heat flux on a surface and you were not solving for the temperature in the plate, we could use the heat flux condition. This could be a function of position and/or temperature and be applied using a Named Expression.



There is no physical quantity of h, it is a construct that people have made that helps simply many problems. But it is not needed to solve for the temperature field. The influence of the velocity field on the temperature (i.e. convection) shows up in the energy equation without using h explicitly.

[hackis20]

Thanks for your feedback

Unfortunately almost people are using gambit in here

As you said i have an intial temperature(850℃) of the plate and the plate is cooled with cold air(25℃) blowed from the inlet velocity 1.5m/s.
The purpose of this analyze is that predict the plate temperature variation by air cooling along the time.(transient)


I understand what you mentioned that heat tranfer coefficient is result of the solution.
then does it mean the coefficient is not dependent variable for energy equation??


I know
- initial temperature of plate
- velocity and temperature of air
- dimension of plate
- material of fluid and plate

I don't know
- heat flux

In these conditions i have the heat transfer coefficient table along the surface temperature of plate. this table is experimental data from some institution.

do you have any idea to make simulation that predict temperature variation along the transient??

[hackis20]

and here is other boundary conditions for plate

this mesh was made by two different volumes.
so there are two face bewteen the interface of two volumes.
each face is defined by wall and convection thermal conditions.
then i could specify heat transfer coefficient i fluent.


one can not specify convection thermal condition(first posted mesh)
and second mesh can specify convection thermal condition and h.(this mesh)

this makes me confusing.

[NickFL]

Originally Posted by hackis20

Thanks for your feedback

Unfortunately almost people are using gambit in here

As you said i have an intial temperature(850℃) of the plate and the plate is cooled with cold air(25℃) blowed from the inlet velocity 1.5m/s.
The purpose of this analyze is that predict the plate temperature variation by air cooling along the time.(transient)


I understand what you mentioned that heat tranfer coefficient is result of the solution.
then does it mean the coefficient is not dependent variable for energy equation??


I know
- initial temperature of plate
- velocity and temperature of air
- dimension of plate
- material of fluid and plate

I don't know
- heat flux

In these conditions i have the heat transfer coefficient table along the surface temperature of plate. this table is experimental data from some institution.

do you have any idea to make simulation that predict temperature variation along the transient??

Yes, you do not know the heat flux. Fluent will calculate the heat flux for you. Then in post-processing it can show you the heat transfer coefficient on the surface (and there will be the wall adjacent temperature quantity too--i.e. T_infinity from our textbooks).



When you are running the transient simulation, be sure to create some monitor points for variables like Temp at certain points, areaAve Temp, and anything else that you need. These will then be computed every time step, and they can be saved to a file or plotted.

[NickFL]

Originally Posted by hackis20

and here is other boundary conditions for plate

this mesh was made by two different volumes.
so there are two face bewteen the interface of two volumes.
each face is defined by wall and convection thermal conditions.
then i could specify heat transfer coefficient i fluent.


one can not specify convection thermal condition(first posted mesh)
and second mesh can specify convection thermal condition and h.(this mesh)

this makes me confusing.

You do not want to specify anything other than the initial temperature of the plate. Let Fluent calculate everything else for you. What you want is an interface between the fluid and the solid. Look up conjugate heat transfer tutorials on google or youtube. There are bound to be many available.