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undesired temperature profile
Posted Jul 16, 2012, 5:09 a.m. EDT Heat Transfer & Phase Change, Parameters, Variables, & Functions, Studies & Solvers Version 4.3 8 Replies
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Hello,
I am trying to control temperature at the center of the model with time. For that I am applying a current (across the terminals) that would be controlled by following the temperature-time profile(using P.I.D) fixed at the center.
I would like to ask, the temp I set as a function of time:
let say, I want temp to raise as 100*t for 6 min.
and then keep it at 600 K for another 4 min.
So do i need to compute the solution for (6+4)min or 600 sec.?????
And what if i simulate it for lesser time, i mean, for 450 sec or so. Could comsol calibrate also the temp for the rest 150 sec by itself?????
The question is, does comsol know about all the above stuff?? How does it work??
Moreover, the problem is, it is not following exactly the temperature I have set.
Please help me out!! I am attaching a file for your ready reference.
(PS: the model i am working in is a 2D model)
*thanks in advance
I am trying to control temperature at the center of the model with time. For that I am applying a current (across the terminals) that would be controlled by following the temperature-time profile(using P.I.D) fixed at the center.
I would like to ask, the temp I set as a function of time:
let say, I want temp to raise as 100*t for 6 min.
and then keep it at 600 K for another 4 min.
So do i need to compute the solution for (6+4)min or 600 sec.?????
And what if i simulate it for lesser time, i mean, for 450 sec or so. Could comsol calibrate also the temp for the rest 150 sec by itself?????
The question is, does comsol know about all the above stuff?? How does it work??
Moreover, the problem is, it is not following exactly the temperature I have set.
Please help me out!! I am attaching a file for your ready reference.
(PS: the model i am working in is a 2D model)
*thanks in advance
Attachments:
8 Replies Last Post Jul 20, 2012, 6:16 a.m. EDT
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Posted:
1 decade ago
Hi
Where do you define your T_cp ?
--
Good luck
Ivar
Where do you define your T_cp ?
--
Good luck
Ivar
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Posted:
1 decade ago
thanks for your reply.. :)
look at the domain probe-1 in the definition node... you can find it there!
look at the domain probe-1 in the definition node... you can find it there!
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Posted:
1 decade ago
Hi
Ah, I have never done it that way ;)
I have always defined a local or global variable with an average operator, probably it works ...
--
Good luck
Ivar
Ah, I have never done it that way ;)
I have always defined a local or global variable with an average operator, probably it works ...
--
Good luck
Ivar
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Posted:
1 decade ago
actually i need that point at the center to follow a temperature profile which i have set for it, (T_set Vs time). And i am using PID algo. for that.
so as per the PID principle, it will calculate the error, difference b/w the temperature what i wanted it to be T_set and the temp what we get after simulation T_cp at the center, and try to minimize it.
How can i define the T_cp globally, because it is the temperature at the middle after getting heated up. we dont know its value? Is there any way to do that? Please let me know...
And I would be grateful to you if you could please help me with the query i asked at the first place, regarding the time for studying the model?
A very kind thanks in advance. :)
so as per the PID principle, it will calculate the error, difference b/w the temperature what i wanted it to be T_set and the temp what we get after simulation T_cp at the center, and try to minimize it.
How can i define the T_cp globally, because it is the temperature at the middle after getting heated up. we dont know its value? Is there any way to do that? Please let me know...
And I would be grateful to you if you could please help me with the query i asked at the first place, regarding the time for studying the model?
A very kind thanks in advance. :)
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Posted:
1 decade ago
Hi
you can always cut your domains with a boundary that intercepts at your desired "point" and then select the point and integrate the value at the poin (point integration on a single point)t, this will give you a Global variable defined at the location of the point
--
Good luck
Ivar
you can always cut your domains with a boundary that intercepts at your desired "point" and then select the point and integrate the value at the poin (point integration on a single point)t, this will give you a Global variable defined at the location of the point
--
Good luck
Ivar
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Posted:
1 decade ago
actually i followed the PID-tutorial model. And they did it that way, and i find it easy, i mean one just need to select the coordinate where you need to study the temp. distribution.
Yours seem to be interesting too. You mean i should draw a line intersecting at the center and then just activate the integration point node and select the intersection point? then what should i do next?how does the comsol know that i want to study the "temperature" at the center?
and suppose i set T_centerpoint, and i want to command the comsol to follow certain temperature-time profile. For that i drew a graph T_set Vs time using piece wise function.
where T_set is
100*t for 0 to 6min--> linearly increasing
600 for 6 to 10 min. -->constant
and study time is from 0 to 600 sec(10 min).
My question is if i set the study time to only 6 minutes or 360 sec. will that temperature be included in the picture? i mean from 6 to 10 min?
and why it is showing negative current value after solving i mean it could have been zero) even if the temperature is positive?
is it just because of the incorrect values of k_proportional, k_integral and k_derivative (three essence of PID)
Did you find any flaw in the model. Are all the boundary conditions correct? please check it. :)
(PS: i set the current at the terminal using PID algorithm.)
And i would be grateful for helping me out. :) :)
Waiting for your reply.
Yours seem to be interesting too. You mean i should draw a line intersecting at the center and then just activate the integration point node and select the intersection point? then what should i do next?how does the comsol know that i want to study the "temperature" at the center?
and suppose i set T_centerpoint, and i want to command the comsol to follow certain temperature-time profile. For that i drew a graph T_set Vs time using piece wise function.
where T_set is
100*t for 0 to 6min--> linearly increasing
600 for 6 to 10 min. -->constant
and study time is from 0 to 600 sec(10 min).
My question is if i set the study time to only 6 minutes or 360 sec. will that temperature be included in the picture? i mean from 6 to 10 min?
and why it is showing negative current value after solving i mean it could have been zero) even if the temperature is positive?
is it just because of the incorrect values of k_proportional, k_integral and k_derivative (three essence of PID)
Did you find any flaw in the model. Are all the boundary conditions correct? please check it. :)
(PS: i set the current at the terminal using PID algorithm.)
And i would be grateful for helping me out. :) :)
Waiting for your reply.
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Posted:
1 decade ago
Hi
you can create a global variable that you use in your equations by using a "Point" integration over a single point.
Understand that the dependent variable T is in fact a field (T(x,y,z,t), but you need a global value myT=T(x=x0,y=y0,z=z0) for that you must define myT = intop1(T) for point integration over the point of interest
Now you can also consider to define a small boundary and take the average temperature over this boundary, your results will be smoother
--
Good luck
Ivar
you can create a global variable that you use in your equations by using a "Point" integration over a single point.
Understand that the dependent variable T is in fact a field (T(x,y,z,t), but you need a global value myT=T(x=x0,y=y0,z=z0) for that you must define myT = intop1(T) for point integration over the point of interest
Now you can also consider to define a small boundary and take the average temperature over this boundary, your results will be smoother
--
Good luck
Ivar
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Posted:
1 decade ago
thanks to your reply. :)
by that you mean like this(please check the model)??
i integrate the point(at the center) and named the variable, to be evaluated, as T_cp.
But now i am encountering problem in meshing domains.
Could you Please tell me what to do next, i need your help.
And also how can i define T_set at the center?
cause i want to calculate (T_set - T_cp) at the center.
Waitng for your reply.
by that you mean like this(please check the model)??
i integrate the point(at the center) and named the variable, to be evaluated, as T_cp.
But now i am encountering problem in meshing domains.
Could you Please tell me what to do next, i need your help.
And also how can i define T_set at the center?
cause i want to calculate (T_set - T_cp) at the center.
Waitng for your reply.
Attachments: