How does dielectric heating actually work?

In summary: So in summary, it is the resonance of the electronic contribution that causes the dielectric heating.
  • #1
Experience111
11
0
Hi everyone,

I'm currently working on a research project about dielectric heating of some materials and I'm trying to understand the physics of this phenomenon before going any further. I'm especially trying to understand the concept of complex dielectric constant and loss factor. I'm completely lost because I keep coming across two contradictory explanations:

  1. The dielectric heating is due to the movement of rotating dipoles (aligning with the alternating electric field) which creates heat
  2. "As the frequency increases further a point is reached where the reorientation polarization fails to follow the applied field and contributes less to the total polarization. The fall of the effective polarization manifests itself as a fall in the [real part of the] dielectric constant and a rise of the loss factor. Energy is now drawn from the system and dissipated as heat into the material"
So on one hand I'm told that it is the movement of the dipoles that causes heat, and on the other hand I'm told that it is the failure of the dipoles to follow the electric field that causes heat which doesn't make much sense to me.

Could somebody be kind enough to help me make sens of it all ? Thank you :)
 
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  • #2
It appears you are basically referring to how "microwave ovens" do their heating. I'm not entirely sure of this, but I believe there is often a resonant frequency of a particular contribution to the dielectric component just before that component drops out. According to Kittel's solid state physics, there are 3 contributions to the dielectric constant: dipolar, ionic, and electronic. On p.411 of his book, he shows a graph of the polarizability as a function of frequency: The dipolar contribution drops off and he shows no resonance in the dropoff, but with the ionic and electronic contributions, there is a sharp temporary increase in the polarizability with frequency, (most likely due to a resonance) before it drops off.
 

Related to How does dielectric heating actually work?

What is dielectric heating?

Dielectric heating is a method of heating a material using an alternating electric field. This is achieved by placing the material between two electrodes and applying a high-frequency alternating current to the electrodes. The material's molecules rotate and collide due to the applied electric field, generating heat in the process.

How does the electric field generate heat?

The electric field causes the molecules in the material to rotate and collide with each other, which creates friction. This friction between molecules produces heat, similar to rubbing your hands together to warm them up.

What materials can be heated using dielectric heating?

Materials that have dipole molecules, such as water, can be heated using dielectric heating. Other materials that have polar molecules or ionic compounds can also be heated using this method.

What are some advantages of dielectric heating?

One advantage is that it can heat materials more evenly compared to other heating methods. Also, there is no direct contact between the material and the heating source, reducing the risk of contamination. Additionally, the heating process is faster and more energy-efficient compared to other methods.

Are there any limitations to dielectric heating?

Yes, there are some limitations. Dielectric heating is only effective for materials that have dipole or polar molecules, so it cannot be used for all types of materials. Also, the heating process is dependent on the material's dielectric properties, so it may not be suitable for materials with low dielectric constants.

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