Note: This discussion is about an older version of the COMSOL Multiphysics^{®} software. The information provided may be out of date.

**Discussion Closed** This discussion was created more than 6 months ago and has been closed. To start a new discussion with a link back to this one, click here.

## Strange behaviour of Microwaves Heating

Posted Nov 26, 2011, 5:43 AM EST RF & Microwave Engineering, Heat Transfer & Phase Change, Results & Visualization, Studies & Solvers Version 4.0a 3 Replies

Dear all,

I am trying to heat the water layer with microwaves heating. The layer of water is trapped between two thick layers of oil.

When I place the microwaves source directly in front of the layer of water and heat it, it shows some temperature distribution as shown in figure attached.Although this temperature distribution does not seem to be right as according to my perception , water is a good absorber of microwaves and it should absorb most of the energy as a result of which temperature of water should rise significantly. But the found is a very small temperature distribution. Is anyone familiar with such trends and the expected results???

But the real problem comes in when I relocate my source above or below the water layer, it gives me error as follows:

Undefined value found.

- Detail: Undefined value found in the stiffness matrix.

There are 1160 equations giving NaN/Inf in the matrix rows for the variable mod1.E10

at coordinates: (0.0016633,0.00180792), (0.00332659,0.00361583), (0.00382242,0), (0.00714901,0.00361583), (0.00764484,0), ...

There are 290 equations giving NaN/Inf in the matrix rows for the variable mod1.E20

at coordinates: (0.00548572,0.00180792), (0.0016633,0.00514125), (0.00469918,0.00847458), (0.0085216,0.00514125), (0.0191354,0.00333333), ...

There are 290 equations giving NaN/Inf in the matrix rows for the variable mod1.E21

at coordinates: (0.00548572,0.00180792), (0.0016633,0.00514125), (0.00469918,0.00847458), (0.0085216,0.00514125), (0.0191354,0.00333333), ...

There are 871 equations giving NaN/Inf in the matrix rows for the variable mod1.Ez

at coordinates: (0,0), (0.0114673,0), (0.00573363,0), (0.00249494,0.00271187), (0.00498989,0.00542375), ...

and similarly for the degrees of freedom, NaN/Inf in the matrix columns

I am surprised with the trend as if it is working fine with the source at one location, it should not have any problem for relocation of the source. It could give us unexpected temperature distribution but heating effect should be there at least.

What you people think about it?

Thanks for any suggestions, comments or discussions etc...

I am trying to heat the water layer with microwaves heating. The layer of water is trapped between two thick layers of oil.

When I place the microwaves source directly in front of the layer of water and heat it, it shows some temperature distribution as shown in figure attached.Although this temperature distribution does not seem to be right as according to my perception , water is a good absorber of microwaves and it should absorb most of the energy as a result of which temperature of water should rise significantly. But the found is a very small temperature distribution. Is anyone familiar with such trends and the expected results???

But the real problem comes in when I relocate my source above or below the water layer, it gives me error as follows:

Undefined value found.

- Detail: Undefined value found in the stiffness matrix.

There are 1160 equations giving NaN/Inf in the matrix rows for the variable mod1.E10

at coordinates: (0.0016633,0.00180792), (0.00332659,0.00361583), (0.00382242,0), (0.00714901,0.00361583), (0.00764484,0), ...

There are 290 equations giving NaN/Inf in the matrix rows for the variable mod1.E20

at coordinates: (0.00548572,0.00180792), (0.0016633,0.00514125), (0.00469918,0.00847458), (0.0085216,0.00514125), (0.0191354,0.00333333), ...

There are 290 equations giving NaN/Inf in the matrix rows for the variable mod1.E21

at coordinates: (0.00548572,0.00180792), (0.0016633,0.00514125), (0.00469918,0.00847458), (0.0085216,0.00514125), (0.0191354,0.00333333), ...

There are 871 equations giving NaN/Inf in the matrix rows for the variable mod1.Ez

at coordinates: (0,0), (0.0114673,0), (0.00573363,0), (0.00249494,0.00271187), (0.00498989,0.00542375), ...

and similarly for the degrees of freedom, NaN/Inf in the matrix columns

I am surprised with the trend as if it is working fine with the source at one location, it should not have any problem for relocation of the source. It could give us unexpected temperature distribution but heating effect should be there at least.

What you people think about it?

Thanks for any suggestions, comments or discussions etc...

3 Replies Last Post Nov 26, 2011, 9:24 AM EST