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M_Kintsch

RADIATION and time scaling

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Hello,

i have a little question about the possibility of time scaling and the use of the radiation load collector.

I used the factor 10 (1sec in simulation=10sec in real time) to speed up my thermal analysis with radioss.

It works fine wenn i scale thermal conductivity and the heat transfer coefficent (for example convection) by the factor i used for speed up (10).

Is this although possible for the radiation? Because i don't see any way to scale this value in correct way...

 

With best regards

Kintsch

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Hi Kintsch,

This /RADIATION is an imposed load condition. in this load card we have a time function identifier ( fct_IDT ) for the temperature of heat source. Here you can create a required time vs temperature function

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I don't think this will work, a little example:

 

Convection:

 

Q=h_conv*(T_1-T_2)

with time scaling by 10 i just go to the h_conv value and scal it with the same value

h_conv=yy*10

 

Radiation:

Q=e*Boltzman_const*(T_1^4-T_2^4)

e = has to be a value between 0 and 1 .. so i don't have the possibility to scale this value over the emissionfactor

 

With the Time vs Temperature i only can scale an constant value, because T_1 is my sourounding Temperature and it is const. 303,15K.

 

With best regards

Kintsch

 

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okay the Solution of the Problem is realy easy.

 

the emission hast to be a value between 0 and 1, but you can define values greater than 1.

So for example if you want to speed up your thermal calculation by a factor of 10 you just need to scale your emission factor.

e (with out scaling) = 0.6

e (with sclaing by 10) =6.0

 

works absolut fine.

If you want to solve radiation problems use the newest Radioss version (2017.2), with older version i had extrem deviations to the real temperature values!

 

 

With best regards

Kintsch

 

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