Radio frequency heating apparatus

In summary, the conversation discusses the topic of radio frequency heating and the speaker's need for links or suggestions on how to make a radio frequency heating apparatus for their specific purpose. They clarify that they need heating by radio waves and not microwaves, and explain that they are trying to heat a reaction mixture using waves with a smaller wavelength, similar to radio therapy for heating malignant tissues. They mention using commercial microwave reactors but have not come across longer wavelength radio wave reactors. The speaker also discusses the use of an RF generator and the need for frequency determination and proper shielding. The conversation ends with a request for help in building an RF generator for their purpose.
  • #1
vaibhava
10
0
Can anyone help me/suggest some links to make a radio frequency heating apparatus?
I need to carry out radio frequency heating (heating by radio waves) of some reactant samples.
Please help..
 
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  • #2
a microwave oven comes to mind :)

Dave
 
  • #3
Yeah that is pretty convenient! But I don't want heating by microwaves. I need radio wave heating. Can you help me out on that?
 
  • #4
vaibhava said:
Yeah that is pretty convenient! But I don't want heating by microwaves. I need radio wave heating. Can you help me out on that?

microwaves IS radio wave heating

maybe you had better explain what you are trying to achieve

cheers
Dave
 
  • #5
davenn said:
microwaves IS radio wave heating

maybe you had better explain what you are trying to achieve

cheers
Dave

Oh ok. Microwaves have a little higher frequency than radio waves. I need to heat my reaction mixture using waves with a smaller wavelength. Its something like radio therapy to heat malignant tissues.
 
  • #6
vaibhava said:
Oh ok. Microwaves have a little higher frequency than radio waves. I need to heat my reaction mixture using waves with a smaller wavelength. Its something like radio therapy to heat malignant tissues.

Sorry my bad. I meant a little smaller frequency.
 
  • #7
Oh ok. Microwaves have a little higher frequency than radio waves. I need to heat my reaction mixture using waves with a smaller wavelength. Its something like radio therapy to heat malignant tissues

Microwaves are just one section of a very wide radio frequency spectrum.
You mean longer wavelength :) Smaller wavelength is even higher microwave radio.

ok medical radiotherapy is not a field of electronics I am familiar with. Have had various treatments in that area tho :(

what specifically are you trying to heat. does the heating speed up the reaction ?
is it a very confined area that need to be heated up so as not to heat up other surrounding material ?

Do you know of any specific commercial equip that uses the same principal ?

Dave
 
  • #8
davenn said:
Microwaves are just one section of a very wide radio frequency spectrum.
You mean longer wavelength :) Smaller wavelength is even higher microwave radio.

ok medical radiotherapy is not a field of electronics I am familiar with. Have had various treatments in that area tho :(

what specifically are you trying to heat. does the heating speed up the reaction ?
is it a very confined area that need to be heated up so as not to heat up other surrounding material ?

Do you know of any specific commercial equip that uses the same principal ?

Dave

I hope your treatment went well :)
I am trying to carry out a reaction by irradiating reaction mixture with radio waves. It speeds up the reaction to a great extent as dipoles in the sample try to align with the alternating electric field, hence producing heat.
I know of commercial microwave reactors. Haven't come across longer wavelength radio wave reactors. One place I saw that RF heating was attained by keeping reaction mixture between two electrodes connected to a RF generator. I am not able to figure out what an RF generator is.
 
  • #9
A RF generator is basically a transmitter, tho in this case for your use, its transmitted energy is probably kept relatively confined ..within a chamber of some sort. In the same way the a microwave oven operates. I guess your real problem is knowing what frequency is needed for your system... that I can't help you with. But once you know that, I and others on this forum will be able to offer suggestions on how to build the generator (transmitter).

The reason that 2.45GHz is used in microwave ovens is because water molecules resonate well at that freq. That resonance (vibration) is what causes the heating ... ie... the hi speed motion of the water molecules within the food.

cheers
Dave
 
  • #10
ok I am off to bed, getting late here in my country and I have to work tomorro :)

maybe some others will chime in with added suggestions, whilst I sleep

good nite
Dave
 
  • #11
davenn said:
ok I am off to bed, getting late here in my country and I have to work tomorro :)

maybe some others will chime in with added suggestions, whilst I sleep

good nite
Dave

oh ok. I will try to determine the frequency which will serve best for my purpose. And then get back to you.

Thanks a lot!
Good night :)
 
  • #12
davenn said:
The reason that 2.45GHz is used in microwave ovens is because water molecules resonate well at that freq.

From Wikipedia: http://en.wikipedia.org/wiki/Microwave_oven
"Microwave heating is sometimes explained as a resonance of water molecules, but this is incorrect: such resonance only occurs in water vapor at much higher frequencies, at about 20 GHz."

While just about any frequency will work, the higher the frequency the more efficient it will probably be. The location where your sample is heated should be RF shielded and the door should be interlocked with the power to the unit to prevent RF exposure to workers. If you are not an expert in RF, you should find someone who is because if you are not careful, you could get RF burns.
 
  • #13
I will have to determine the best frequency for my purpose by actually conducting the experiment. I think an optimum frequency between 10-100 MHz should work for me.
Can you help me make an RF generator for that?

I will take caution in shielding the waves by enclosing the reaction mixture and the electrodes in a cavity..
 
  • #14
You can apparently still buy DIATHERMY machines, although they are expensive.

These used to be an oscillator on about 27 MHz using large transmitting vacuum tubes.

If the shielding was not good, the devices could radiate a very rough signal and cause interference. Since they had power supplies that were not even filtered, the signal was very rough.

You may be able to find circuits for these, although building one to meet current regulations would be a big challenge.
 
  • #15
I tried to find about various diathermy apparatus and found them too costly for my work.
So I want to build an RF generator that could serve my purpose of RF heating.
Can you please help me on how to make it?
Or if you could give me some links where I can get the required help?
 
  • #16
This is not a trivial project. How much experience do you have with building RF transmitters?

I once worked with an RF dryer that ran at 5000 volts at 1 amp on 27 MHz. The radio tube was the size of a soccer ball. The oscillator was tuned plate, tuned grid (TPTG) and as soon as the oscillator began oscillating the grid was detuned to prevent the tube from overheating. The oscillation was detected with a photocell against a small florescent tube that wasn't connected to anything. If the oscillation was lost for any reason, the power was immediately killed.

Why do you want to use RF heating instead of much simpler electric or radiant infrared heating?
 
  • #17
Due to not much demand of low capacity RF heating system, is quite expensive to get RF system whereas 500 W of mcirowave oven with magntron one can buy readily in $30.

Designing comlete RF generator for small capacity is not worth of your effort. I would suggest you to buy 500 W RF generator (best place to start is ebay). If not avaialbe then new one will cost you $6000. Instead of going for automatic netowrk analyzer and connecting with 50 ohm coaxial cable to the parallel plate eletrodes, you can use a set of variable capiator and inductor. You can cotnact me for further help on design. I have assembled such unit for our reseach purpose.
 

FAQ: Radio frequency heating apparatus

What is a radio frequency heating apparatus?

A radio frequency heating apparatus is a device that uses electromagnetic waves in the radio frequency range to generate heat in materials. It is commonly used in industrial settings for processes such as drying, curing, and welding.

How does a radio frequency heating apparatus work?

A radio frequency heating apparatus works by creating an electric field between two electrodes, typically in the form of metal plates. This electric field causes polar molecules in the material being heated to rotate, which produces heat. The heat is generated throughout the material, rather than just on the surface, making it a more efficient heating method.

What types of materials can be heated with a radio frequency heating apparatus?

A radio frequency heating apparatus can be used to heat a wide range of materials, including plastics, rubber, textiles, wood, and food products. The material must have polar molecules in order for the radio frequency waves to generate heat.

What are the advantages of using a radio frequency heating apparatus?

There are several advantages to using a radio frequency heating apparatus. It is a fast and efficient heating method, with the ability to heat materials evenly throughout. It also allows for precise control of temperature and can be easily integrated into automated production processes. Additionally, it does not require preheating or contact with a heating element, reducing the risk of damage to the material.

Are there any safety considerations when using a radio frequency heating apparatus?

As with any type of industrial equipment, there are safety considerations to keep in mind when using a radio frequency heating apparatus. It is important to follow all safety protocols and guidelines, including wearing protective gear and ensuring proper grounding of the apparatus. Additionally, only trained and qualified personnel should operate the apparatus.

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