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-   -   Transient heat transfer (http://www.cfd-online.com/Forums/fluent/32252-transient-heat-transfer.html)

Jonas October 3, 2003 10:35

Transient heat transfer
 
I would like to perform a simulation of a hot solid being cooled by an airstream of constant temperature. At time=0 the temperature of the solid is known and I would like to find out the temperature after x seconds. How can I set up this case in Fluent? Fluent asks for a boundary condition for the wall of the solid but the only thing I have is an initial condition. How is the temperature in the solid set?

Thanks!

Jonas Larsson October 6, 2003 09:05

Re: Transient heat transfer
 
The initial condition is set when you initialize your flow-field before you start running the transient simulation. However, often you want to run the simulation a bit first to get a developed flow field before you start the transient. The way to do this is to have the solid in a separate zone. You can then patch a new temperature into the solid zone before you start the transient simulation. I haven't actually tried this in Fluent but I think that it should work well, if I'm wrong someone please correct me.

Prabu Parthasarathy October 7, 2003 11:34

Re: Transient heat transfer
 
Jonas,

The way I would solve this problem is break the solid into two solids, an inner one and an outer one. On the boundary of the inner one (the interface between the two solids), set your initial temperature as boundary condition and run the model for a steady state solution. Once you have the steady state solution, define the interface to be an "interior" type.

Once you do this, you do not need to define any boundary condition and you also have a good initial solution. Set the outer boundary to be a convection type for both the SS and transient models.

Prabu

venugopal October 18, 2003 01:57

Re: Transient heat transfer
 
Haaai First you select the domain for fluid region. And, If you are doing natural convcetion in unsteady state you can select boussinique apporoximation, in the material panel and give the beta value and in models you select unsteady state. If you are giving extended domin for fluid region, the interface of the solid and fluid region will be taken automatiaclly as couple. So, you dont worry about that one. And in interation panel, you give the time and number of time steps and then iterations per time step. You can create one separate window for monitoring the temperature, you go to Solve-monitors-surface and there you can select the surface whatever you want. you select write and monitoring option. after completion of the programme you can import these temp. monitored data file to excel and you can find the time easily


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