Heat transfer coefficient in Code-Aster

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15 years 3 weeks ago #2671 by tsachi
Replied by tsachi on topic Re:downloading caelinux
it works now.
Thanks

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11 years 5 months ago - 11 years 5 months ago #6473 by Alex

Johannes Erben wrote: Hello,
- Is there a implementation of a heat transfer coefficient in Code-Aster that describes the heat transfer from solid to liquid/gas (unit: W/(m^2 K)).


Oh my, just the same as my problem. Could anyone, please help me with the answer or any example how to get heat flow value in Code-Aster W/(m^2 K).

Unfortunately links from the second post are dead.
Last edit: 11 years 5 months ago by Alex.

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11 years 5 months ago #6474 by Alex
I've already made some progress with that problem thanks to Kai Velten book. He says:
The ‘‘imposed flux’’ option of the wizard can be used to impose boundary conditions involving a heat flow across the boundary...

But the main question remains: hot to get the numbers of the boundary heat flow?

Please, help, anyone!

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11 years 5 months ago - 11 years 5 months ago #6475 by kwou
Hoi


for what it is worth:

sthing=AFFE_CHAR_THER(MODELE=FemQuad,
FLUX_REP=_F(GROUP_MA='Face_1',
FLUN=100.0,),
RAYONNEMENT=_F(GROUP_MA='Face_2',
SIGMA=5.67e-08,
EPSILON=0.8,
TEMP_EXT=20.0,),
ECHANGE=_F(GROUP_MA='Face_2',
COEF_H=5.0,
TEMP_EXT=20.0,),);


Lval=DEFI_FONCTION(NOM_PARA='TEMP',NOM_RESU='LAMBDA',VALE=(-200.0,180.0,
10000.0,180.0,
),);

RHOval=DEFI_FONCTION(NOM_PARA='TEMP',NOM_RESU='RHO_CP',VALE=(-200.0,2400000.0,
10000.0,2400000.0,
),);


alum=DEFI_MATERIAU(THER_NL=_F(LAMBDA=Lval
RHO_CP=RHOval,),);

I **think** I got/stole/obtained this from Johannes.

Have a further look at U4.44.02, chapter 3.
An example/verification is given in V4.05.300 (see chapter 1.1 for drawing), referring to ..../astest/TPLP300 (also attached):

....
MATER=DEFI_MATERIAU( THER=_F( LAMBDA = 52.,RHO_CP = 1.) )
....
CHTH=AFFE_CHAR_THER( MODELE=MOTH,
TEMP_IMPO=_F( GROUP_NO = 'NO_TIMP', TEMP = 100.),
ECHANGE=_F( GROUP_MA = 'MA_CONV', COEF_H = 750.,
TEMP_EXT = 0.) )
....

Temp=100 means a temperature imposed on group_no='no_timp´
coef_h= 750 [W/m2/k] is convection coefficient to temp_ext=0 for group_ma='ma_conv'
lambda =52 [W/m/K]

Interest: structural mechanics, solar energy (picture at 'my location' shows too little pv panels)

--
kind regards - kees
Attachments:
Last edit: 11 years 5 months ago by kwou.

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11 years 5 months ago #6476 by Alex

keeswouters wrote: Hoi
for what it is worth:

Thanks a million for the answer! But first of all I wanted to tell that I'm a total noob, so I actually didn't get a thing that you've written down for me.
My profession is HVAC (heating, ventilation and air-conditioning) engineering. And I'm trying to use Salome / Aster to calculate heat transfer in an exterior wall or an envelope of the building in order to find out the resistance to heat transfer. So I need to know heat flow rate per square meter. All my knowledge now is just some video examples, so I'm terribly sorry if my questions will sound too stupid.
I will list my misunderstandings below:
1) For instance, In which file should I put a code that you’ve given me? That one that you’ve *got/stole/obtained this from Johannes*.
2) How this code of yours will effect in calculations or how or where I should look for the heat flow values I’m looking for?
3) I also don’t have an idea what to do with that code from TPLP300.comm? I mean where to put it?
Actually I’m already happy that someone at least answered me. Maybe you could help me out with some simple example which I could open in Salome as it is? Because now it’s like an ocean for me.

P.S. I also have another BIG question that might kill all the need in Salome:
As I’ve seen in Thermal analysis examples you can specify only one value for lambda coefficient (coefficient of heat conductivity) for all the geometric figures you have in your file. And then you specify different temperatures for the figures. But in my case I’ve got temperature on the outer surface but every figure can have different lambda. Is that possible to do in Salome / Code-Aster?

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11 years 5 months ago #6479 by Marco
Hi, to solve your problem you can't use salome wizard, all the command you want to use in salome will be contained in a example.comm file , wizard create an example.comm file in the working folder, to compile in a easy way the example.comm file you can use efficace in salome (button on the righ tside of the toolbar) and choose the example.comm file create by wizard.
Once compiled (using efficace) your .comm file come back in salome/aster choos ad new case and select your .comm file.
Efficace is very user friendly and follow you step by step in compiling aster command file (take in to account that all aster documentation could be found www.code-aster.org/V2/doc/v10/en/?lang=en)
the command you interested would be something like this:

LOADING=AFFE_CHAR_THER(MODELE=MODEL,
ECHANGE=(_F(GROUP_MA='imp',
COEF_H=2000,
TEMP_EXT=437,),)

to give different lambda (constant in temperature?) you have to define different solid in geometry environment or different solid_group, in first case you have to create a compound

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