General > General Technical Chat
What happened to RF cooking?
Marco:
I wonder if I overestimate how high the voltages have to be, meat is salty water as far as the signal is concerned, which has a very high dielectric constant. So it will pull all the potential towards itself. A single kV might be enough.
NiHaoMike:
--- Quote from: Marco on June 17, 2023, 12:23:22 am ---I wonder if I overestimate how high the voltages have to be, meat is salty water as far as the signal is concerned, which has a very high dielectric constant. So it will pull all the potential towards itself. A single kV might be enough.
--- End quote ---
Big Clive had great success with a mere 240V applied using electrodes. A bit too intense, actually.
If you use capacitive coupling instead, you'll just have to calculate the reactance the capacitance would add.
Marco:
Oops, I turned it around ... the high k dielectric will cause a large capacitance, which will have the least voltage across. So back to 10s of kV to put a couple 100 Watt into a steak.
The sidewalls in an oven are a bit of a bother as well. Industrial heaters can just have a giant air cavity and tell people to stay away, the cavity in an oven is shielded. You'd make the inner chamber slotted obviously, but all the capacitance to ground (the shield) will bunch the voltage in the middle, without adding yet more capacitance to even it out. All that capacitance is going to draw circulating current, annoying for both efficiency and the driver.
KaneTW:
I'd gladly spend ~2-3k on an oven that can actually uniformly (i.e. not just the surface, and not the spots that regular microwave cause) heat food.
tom66:
--- Quote from: KaneTW on June 17, 2023, 11:38:22 pm ---I'd gladly spend ~2-3k on an oven that can actually uniformly (i.e. not just the surface, and not the spots that regular microwave cause) heat food.
--- End quote ---
For microwaves, you want one with an RF stirrer. Panasonic make a number of "inexpensive" consumer ovens with this function, e.g.
https://www.panasonic.com/uk/consumer/home-appliances/microwaves/combination-microwaves/nn-df386bpq.html
We have a similar one at work. It's weird not having a turntable to put things on. But you can put something in it at any position and it's even throughout.
I was looking at this one for our kitchen but unfortunately the oven function requires a lot of space behind the oven to be kept clear, so wouldn't work where we wanted it.
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