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Pulse input Rectangular Waveguide

Posted Jan 21, 2014, 9:17 p.m. EST 5 Replies

Avinash Gupta
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Hi everyone,

Is it possible in comsol to give a pulse shape input to a port of rectangular waveguide as a power source.? Actually I want to heat a certain material inside a rectangular waveguide for some time (say for 0-10s) and after 10s (say for 10-20s) see its cooling behaviour, that how much the material retain its temperature after turning off the power.?? Just like the microwave oven Problem.

Is there something like this possible in comsol.??
Can someone open the discussion forum and help me.??

Thanks in advacne..
5 Replies Last Post Oct 12, 2016, 7:46 p.m. EDT
Robert Koslover Certified Consultant
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Posted: 1 decade ago Jan 22, 2014, 12:23 p.m. EST
Ten seconds is an eternity on a microwave time scale. From an RF perspective, you might as well solve the heat-input problem using the CW formulation. But even better, for a rectangular waveguide driven by a single mode, you can easily compute the heat dissipation in the waveguide walls analytically (see any good RF or electromagnetics textbook). So, if I were doing your problem, I'd solve only the thermal part of it using Comsol Multiphysics, while using an analytic expression for the RF heating term, as applied to the waveguide walls.
Ten seconds is an eternity on a microwave time scale. From an RF perspective, you might as well solve the heat-input problem using the CW formulation. But even better, for a rectangular waveguide driven by a single mode, you can easily compute the heat dissipation in the waveguide walls analytically (see any good RF or electromagnetics textbook). So, if I were doing your problem, I'd solve only the thermal part of it using Comsol Multiphysics, while using an analytic expression for the RF heating term, as applied to the waveguide walls.
Avinash Gupta
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Posted: 1 decade ago Jan 22, 2014, 11:44 p.m. EST
Thanks for your Answer.

Actually I am new to Comsol.

what I am trying to do is, place a water filled cylinder tube inside a waveguide and apply a piecewise function as input power source to the input port of the waveguide.

My function is

0-5s = 10W
5-10s=0W

What i am trying is, to apply power for just 5s and see the rising temperature (initially 25 degC), and after 5s turning off the power to see how much time water filled tube or pipe will take to reach its initial temperature.??

Is something like this possible.?
Thanks for your Answer. Actually I am new to Comsol. what I am trying to do is, place a water filled cylinder tube inside a waveguide and apply a piecewise function as input power source to the input port of the waveguide. My function is 0-5s = 10W 5-10s=0W What i am trying is, to apply power for just 5s and see the rising temperature (initially 25 degC), and after 5s turning off the power to see how much time water filled tube or pipe will take to reach its initial temperature.?? Is something like this possible.?
Avinash Gupta
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Posted: 1 decade ago Jan 22, 2014, 11:44 p.m. EST
Thanks for your Answer.

Actually I am new to Comsol.

what I am trying to do is, place a water filled cylinder tube inside a waveguide and apply a piecewise function as input power source to the input port of the waveguide.

My function is

0-5s = 10W
5-10s=0W

What i am trying is, to apply power for just 5s and see the rising temperature (initially 25 degC), and after 5s turning off the power to see how much time water filled tube or pipe will take to reach its initial temperature.??

Is something like this possible.?
Thanks for your Answer. Actually I am new to Comsol. what I am trying to do is, place a water filled cylinder tube inside a waveguide and apply a piecewise function as input power source to the input port of the waveguide. My function is 0-5s = 10W 5-10s=0W What i am trying is, to apply power for just 5s and see the rising temperature (initially 25 degC), and after 5s turning off the power to see how much time water filled tube or pipe will take to reach its initial temperature.?? Is something like this possible.?
Robert Koslover Certified Consultant
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Posted: 1 decade ago Jan 26, 2014, 11:00 a.m. EST
OK, that's still similar. First compute the heating-rate of the water with the microwaves in cw (aka, frequency domain) mode. Then use that result to define your volumetric heating condition in a thermal model.
OK, that's still similar. First compute the heating-rate of the water with the microwaves in cw (aka, frequency domain) mode. Then use that result to define your volumetric heating condition in a thermal model.
Chang Liu
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Posted: 8 years ago Oct 12, 2016, 7:46 p.m. EDT
Hi, Avinash:

Now I have the similar situation like yours. How did you solve your question at that time?

Any help is appreciated.

- Chang
Hi, Avinash: Now I have the similar situation like yours. How did you solve your question at that time? Any help is appreciated. - Chang

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