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Making a loop in comsol

Posted Feb 21, 2020, 6:05 p.m. EST Heat Transfer & Phase Change, Computational Fluid Dynamics (CFD), Parameters, Variables, & Functions 3 Replies

Bilal Habashi
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Hi,

I wanted to make a loop in COMSOL for the inlet temperature but this temperature would be different in each time step. Step 1: T_in(0s)=10C Step 2: T_in(1s)=T_out(0s)+T_load(1) Step 3: T_in(2s)=T_out(2s)+T_load(2) and so on. The simulation is just a Uloop pipe and and there is an inlet and outlet. The outlet is defined as heat outflow. As I know the outlet temperature is defined as "root.comp1.out1" in comsol.

Thanks.

3 Replies Last Post Feb 24, 2020, 11:06 a.m. EST
Lars Dammann COMSOL Employee

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Posted: 5 years ago Feb 24, 2020, 3:20 a.m. EST

Hi Bilal, you can specify boundary conditions that depend on time, for example you can define T to be 20[degC]+t*1[K/s] to start with 20° at t=0 and then increase the temperature over time. You can also define helper functions to make this easier. Please note that your boundary conditions should be continuous in time. If you have sudden jumps, you may want to use the events interface. This blog shows an example of that: https://www.comsol.de/blogs/implementing-a-thermostat-with-the-events-interface/

Best wishes, Lars

Hi Bilal, you can specify boundary conditions that depend on time, for example you can define T to be `20[degC]+t*1[K/s]` to start with 20° at t=0 and then increase the temperature over time. You can also define helper functions to make this easier. Please note that your boundary conditions should be continuous in time. If you have sudden jumps, you may want to use the events interface. This blog shows an example of that: https://www.comsol.de/blogs/implementing-a-thermostat-with-the-events-interface/ Best wishes, Lars
Lars Gregersen COMSOL Employee

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Posted: 5 years ago Feb 24, 2020, 4:24 a.m. EST

This model

https://www.comsol.com/model/convective-heat-transfer-with-pseudo-periodicity-12057

Should give you an idea of how to do what you describe.

-------------------
Lars Gregersen
Comsol Denmark
This model https://www.comsol.com/model/convective-heat-transfer-with-pseudo-periodicity-12057 Should give you an idea of how to do what you describe.
Bilal Habashi
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Posted: 5 years ago Feb 24, 2020, 11:06 a.m. EST

Thanks for your help. I learned new things from them but these two examples were dealing with different scenarios of mine: 1. for the thermostat there is an on/off point scenario 2. and the convective heat transfer with phseudo periodicty is related to different sections (I used this model before for two pipe in which I could , but for me it is not the boundry condition. it is various inlet temperatures (for a pipe) but the problem is the outlet temperature (heat outflow) of first step is going to be the inlet temperature for the second step.

I really appreciate your help.

Thanks for your help. I learned new things from them but these two examples were dealing with different scenarios of mine: 1. for the thermostat there is an on/off point scenario 2. and the convective heat transfer with phseudo periodicty is related to different sections (I used this model before for two pipe in which I could , but for me it is not the boundry condition. it is various inlet temperatures (for a pipe) but the problem is the outlet temperature (heat outflow) of first step is going to be the inlet temperature for the second step. I really appreciate your help.

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