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coupling compression heating and heat transfer

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Hi,
I just started working with Comsol, because I want to solve the following problem:
I am compressing a polymer, which results in a compression heating. The adiabatic case can be calculated with the Joule-Thomson-equation: (alpha*T*delta p)/(rho*cp)
I solved this iterative in Matlab for fast compression (adiabatic) and the results are in good agreement with my measurements.
Now I want to combine the compression heating with heat transfer using Comsol. That occurs when the pressure is applied slower. For example, a pressure of 10 bar could be applied in 0.1 or 1 s. The slower the compression, the more time is for heat conduction.
After some tutorials, the heat transfer itself isn't problem. I tried adding a heat source, but even if I would calculate Q in Matlab, I couldn't implement it time-dependent. As the heating itself depends on the temperature (T) and the density (rho) depends on the increase in pressure (delta p), I couldn't find a way to define it as a variable in the global definitions either.
But I am looking for a way to couple it with a time-dependent heat source.

Any suggestions, what I could try to couple my heat transfer with a time-dependent heat source ?

Thanks a lot,
Natalie

2 Replies Last Post 19.12.2015, 04:36 GMT-5
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Hello Natalie Rudolph

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Posted: 1 decade ago 16.10.2010, 20:54 GMT-4
Natalie,

I'm attempting a similar problem, but rather than compressing a polymer, I'm compressing air, which I would like to treat as an ideal gas. Could you tell me how you managed to do the compression heating portion? I can't even get that to work.

Thanks!
Natalie, I'm attempting a similar problem, but rather than compressing a polymer, I'm compressing air, which I would like to treat as an ideal gas. Could you tell me how you managed to do the compression heating portion? I can't even get that to work. Thanks!

Abdulrahman Al Rumaidh

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Posted: 9 years ago 19.12.2015, 04:36 GMT-5
Hi,

One of the conditions for the Joule-Thomson effect to be valid is to NOT to treat the gas as an ideal gas.

Check this useful link:

www.comsol.com/multiphysics/joule-thomson-effect

Regards,
Hi, One of the conditions for the Joule-Thomson effect to be valid is to NOT to treat the gas as an ideal gas. Check this useful link: https://www.comsol.com/multiphysics/joule-thomson-effect Regards,

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