Jones, eventually you can adjust the shape and type of the fuel until it becomes conductive enough and has sufficient area to capture the time changing field and absorb power. The Russian team that uses an inductive heating technique described by MFMP pressed their fuel into pellets that have the right area and resistivity to work with their RF generator. In that case the normal heating resistor coil is not needed.
I have not studied the standard cooking drivers but would be surprised to find that they would work efficiently into a object with a small surface area. You would be wise to construct a drive coil that has an inner area that comes closer to matching the fuel pellet. That way much of the magnetic flux inside the main coil is linked to the pellet. A tighter coupling would allow the reflected resistive component due to the fuel losses to appear larger in the main drive loop. RF current flowing within the main loop would induce power into the reflected resistance from the pellet and if the unloaded 'Q' of the main loop inductor is large enough, most of the input power ends up in the pellet and not as losses within the drive system. You can use resonating capacitors to cancel the input inductive component if you are skilled in the RF field. With careful matching of this type, you can come up with an overall system that efficiently converts the DC input power into pellet heating. But, it takes very careful and skillful design to make it happen. Dave -----Original Message----- From: Jones Beene <[email protected]> To: vortex-l <[email protected]> Sent: Fri, Mar 20, 2015 12:20 pm Subject: RE: [Vo]:Am I the only one.. Dave Ø Jones, even at 40 kHz it is going to be extremely difficult to get enough current to flow inside a coil of wire. Remember, they normally drive the expansive sheet of resistive metal that has an effective resistance that is much less than an ohm. The coils that we are using is in the vicinity of 10 ohms. Yes, that is true but don’t forget that the tube fill mix can be made conductive as well. This is the reason I suggested to Jack to use Fe3O4 instead of Fe2O3 as the bulk fill (or support material) with an inductor setup. The former is 6 orders of magnitude more electrically conductive than the later. So, you have a magnetic field that enters a much larger area of resistive metal when a pan is placed upon the unit than with the small coil. Then, the length of wire used in the coil has a large series resistance whereas the pan is more of a parallel resistance and much less in total value. Both of these effects are working against you. I agree but Fe3O4 is highly conductive - although we do not know what happens at elevated temperature in the presence of reducing compounds, but as long as it is not further oxidized, Fe3O4 should be in the few Ohm range, no? Not to mention acting as a transformer coil, to an extent. Jones
