Temperature Dependent Convective BC for Conduction

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Coffer_001
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Re: Temperature Dependent Convective BC for Conduction

Post by Coffer_001 »

Responding to your most recent response where you did your own evaluation, you are solving a different problem that what I need to address. I need to work with specific time dependent experimental data as boundary conditions. You are correct that the heat equation does not respond as fast as the wave equation and we have to temper our expectations.

I agree with you that Convective Heat Transfer Coefficient (hc) and External Temp (Tinf) works well. What is not working (given my execution) is when hc is coupled with an External Temp that is time dependent OR hc and Temp = Variable Time.

Am I making sense? I can reword if necessary. We all communicate differently.

Again I thank you for your tenacity!
Coffer_001
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Re: Temperature Dependent Convective BC for Conduction

Post by Coffer_001 »

You are WONDERFUL! I'll continue to struggle as well, but believe I am at the end of my rope.
kevinarden
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Re: Temperature Dependent Convective BC for Conduction

Post by kevinarden »

In my simple case it behaved well with
Boundary Condition 1
Target Boundaries(4) = 1 2 3 4
Name = "BoundaryCondition 1"
Heat Transfer Coefficient = 1.001
External Temperature = Variable Time
Real
0 120
20 120
40 240
60 120
80 60
100 30
2000 0
End
End
variable1.png
(123.01 KiB) Not downloaded yet
kevinarden
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Re: Temperature Dependent Convective BC for Conduction

Post by kevinarden »

It did not do so well with this input, I would have thought it would get much hotter
External Temperature = Variable Time
Real
0 120
20 120
40 240
60 480
80 500
2000 1200
End
curve2.png
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kevinarden
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Re: Temperature Dependent Convective BC for Conduction

Post by kevinarden »

although this did work
Temperature = Variable Time
Real
0 120
20 120
40 240
60 480
80 500
2000 1200
End
case3.png
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kevinarden
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Re: Temperature Dependent Convective BC for Conduction

Post by kevinarden »

Do many iterations it appears that
External Temperature does not work with variable time
Heat Transfer Coefficient does work with variable time
Temperature boundary works with variable time, but does not care about h,
I guess sine it is a specified temperature it does not look at h.

It would seem that if you want the temperature boundary be a function of time variable with a time varying h, then you have to do that calculation yourself
and apply it as a Temperature = Variable Time
Real
time temp

where temp = External Temp times h, that you have to calculate temp.
If you need to do it during the simulation for some reason you can create your own external function.

Temperature = Variable Time
Real Procedure "MyCode" "MyFunction"
Coffer_001
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Re: Temperature Dependent Convective BC for Conduction

Post by Coffer_001 »

Thanks for investigating and providing your comprehensive assessment!
Rich_B
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Re: Temperature Dependent Convective BC for Conduction

Post by Rich_B »

Hello,

Could you provide more info about this statement:
...work with specific time dependent experimental data...
Is there a journal article that is close to your situation, something in the public view that would help describe your problem?

Or perhaps you could make up some numbers, put them into a spreadsheet table, and then share that with us?

Thanks, Rich.
Coffer_001
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Re: Temperature Dependent Convective BC for Conduction

Post by Coffer_001 »

Hi Rich B:

I have a flat plate that is in an oven. I know the gas temperatures inside the oven and they are given as a function time in the boundary condition 1 listing. I also have temperature sensors on the plate that are separated from the oven temperature by some process aids. Since the gas temperature (Tg) does not equal the plate surface temperature (Ts), I can be sure the convective heat transfer coefficient is not infinity. What I am trying to do is to estimate the hc for various temperature ranges by assuming an hc and iterating until Ts = Tg at that time. I'm trying to solve a basic conduction problem with time dependent convective boundary conditions: hc(Ts-Tg).

Am I communicating clearly? We you like me to explain anything further/different?

Thanks for your interest!
kevinarden
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Re: Temperature Dependent Convective BC for Conduction

Post by kevinarden »

Since External Temperature = Variable Time is not working
and Temperature = Variable Time does not use h
Then if I can make Temperature = Variable time as a function of External Temperature and h
it may over come the problem.
MyCode.F90
(1.2 KiB) Downloaded 31 times
case4.png
(141.75 KiB) Not downloaded yet
The above works numerically but, it is only meaningful if the function is meaningful.
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