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Coriolius October 4, 2004 11:54

How to define heat flux
I am new to STAR-CD. I am trying to model a problem of air flowing over some heat producing machine in a confined space with ventilation. I can define the shape of the machines and the heat producion rate are known. In that case, the average heat power release per unit area is known. The surface temperature are unknown and has to be determined.

But how can I define the heat flux value in STAR-DESIGN? In the BOUNDARY field, only the TEMPERATURE field is available after I checked the "ENERGY EQUATION" in the SOLVER PROPERTIES.

Anyone can give me advices or comment?

Brian October 4, 2004 12:23

Re: How to define heat flux
I would recommend opening your model in Prostar, and specifying the boundary condition there.

StarDesign has a limited feature set, mostly to make it easier to use, but this means the more advanced functionality has to be left out of the interface.

Coriolius October 4, 2004 21:27

Re: How to define heat flux
In that case, can I make/import an initial model in Star-Design, save it, then edit it in Pro-Star to input? Or in other words, are the Pro-Star and Star-Design share the same kind of project files?

Brian October 5, 2004 02:08

Re: How to define heat flux
Exactly the same. You should have no trouble opening a model, saved in StarDesign, in Prostar.

Vice versa, I'm not so sure.

new-user October 5, 2004 03:40

Re: How to define heat flux
or... in the stardesign solver parameters you have an option of connecting a file with additional data. so write a text file with starcd commands defining your heat flux boundary and just give there a path to it if you really need to solve it in stardesign. I did it once for an excercise and it is working. good luck.

Coriolius October 5, 2004 05:43

Re: How to define heat flux
Thanks for the advices

Coriolius October 6, 2004 11:17

Re: How to define heat flux
Now, I have created the domain by boolean operation in STAR-DESIGN and create the boundary that will be given a constant heat flux. I can get the surface number of these surface (NOT meshed yet) eg. surface no. 19, 20, 22, 25 etc. The heat flux is 7000 W/m2

Can you list a demonstration example of the additional pre-prpcessing input file that would describe that boundary conditions?

new-user October 7, 2004 04:35

Re: How to define heat flux
rdef,29,wall,standard nosl,stand,9, 0,0,0,1,0 flux,20.6235

so the boundary number is 29 and I applied the flux of 20.6235 W/m2, but I cannot swear that it corresponds to your stardesign surface number. just check it on something very simple...

to see the explanation of the command rdef, type help rdef in the prostar output window.

hope it helps

Coriolius October 8, 2004 22:05

Re: How to define heat flux
Thanks. The command line also work for my situation. But another annoyong problem arise.

Please read the new thread "Outflow conditions causing ERROR #064"

Coriolius October 11, 2004 05:44

Re: How to define heat flux
I have made a class of boundary and several regions need to be assigned to this kind of boundary.

Let's call it "HEATER" and region# 12, 13, 14, 18, 20 should be assigned to it

If I want to assign a heat flux value to this kind of boundary at one time, what command can we use? Could we use the RDEF command?

Is it possible to create a variable which contains the values of these region number, and then use the variable as input to the RDEF command?

new-user October 11, 2004 08:59

Re: How to define heat flux
Hi Coriolius,

I think that you should define your boundary using so called table (but I guess there are some limitations on the length of such a table) or the user suboutine to change your boundary values over time. for the details consult the prostar user guide.

for exchange ;-) : do you know what is the 'pseudotransient' state??? does it mean that we discretise the time independent equations and put inside time as a parameter???

Coriolius October 13, 2004 01:36

Re: How to define heat flux
The only source of information about Pesudo-transient method is from their METHODOLOGY manual. But I can only find description about the algorithms such as SIMPLE, PISO, SIMPISO etc. But there is no further detail about the subject on qseudo-transient.

Sorry, can't help you.

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