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Hi

the Boolean expression"*(t[1/s]<=900)" is equal to 1 so long t<=900 seconds and is =0 from t>900 seconds. But this BC condition has a step and the BC is not derivable, I precognise to use a "step()" operator to have a smooth transition, and then to set your time series to force 2-3 steps around th etransition at 900 seconds, and do not forget to set the solver time stepping (lower level sub-sub... node) to intermediate or strict and not "free"

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Good luck
Ivar

Hello;

Thank very mutch for your request;

Can you explain me how to represent a heating time of 30 min and a cooling time of 180 min in COMSOL "heat transfer module" time-dependent.

Thank you in advance;
Have a great day;

Hi

1) apply a heat source with a Q value Q0*(t<=900) is one way
2) apply a hea source with Q=Q0*stp1(t) with stp1 operator defined as 1 for t<= 900 and 0 above
3) apply two time series in sequence, one for 0<=t<=900 (+ store solution) and a second for t>= 900 sec and adapt the BC's accordingly (solve settings to enable/disable the different BC's

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Good luck
Ivar

Thank you very mutch;

I have understood from you that if i want to do 15min of heating time i can use Q0*(t<=900);
Now, i want to understand what am i going to do for cooling time (of 60min for example);

Thank at advance for you for you help;

Hi

Q0*(t<900) is equal to Q0 so long t< 900 and equal to "0" no heating for t>900

So you ahve stopped heating, now you could add beforehand a convecting cooling noode for all entities (I replied to a similar model question last week I beleive, (check the Forum withj a search) this will also cool when heating, but in most models I would say this is true.

But there are a faire chance that COMSOL will exclude the entitiy (BC surface) from the cooling for which you have defined the heat source, as these BC are not additive.

Then you need to use two time solvers (one for 0<t<900, and one for t>900) and the conditional BC enable/disable functinality in the dolver node (>= v4.3a), to avoid that COMSOL overwrites the results, you must add manually a "store solution node in the dolver sequence between the two time stepping solver study nodes

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Good luck
Ivar

Good Morning;


I want to install livelink for excel, but i can't install it;
Please try to help me;

How to install live link for excel 2010?



Thak you very mutch at advance