Jones-- You indicated that ferromagnetic nickel is better for induction devices—i.e., in the part which is heated. Why?
It’s the driving (variable) magnetic field that induces eddy currents in the heated parts (per some of the conversation heretofore in this thread) that is important. It would seem that a good conductor with the right resistance would be what matters most. The hysteresis of ferromagnetic materials would seem to make no difference in a varying magnetic field, unless the local B fields in the heated material affects the transfer of energy other than by the resistance heating of electrons in an eddy current. The time constant of the heated for response to a changing magnetic field may be a key parameter. Bob Cook From: Jones Beene Sent: Monday, June 15, 2015 9:06 AM To: [email protected] Subject: RE: [Vo]:The good, the bad and the ugly From: Daniel Rocha Ø Why not heating it with magnetic induction? Induction makes sense – at least for the entry level experiment, based on these considerations 1) Cost – 1500 watt microwave oven costs $150 – whereas 1800 watt induction cooktop is $75 2) Efficiency – microwave is nominally 75% efficient and cooktop is 84% efficient 3) Ease of access - microwave has door that must remain closed and cooktop is open 4) Coupling of energy – this is the big unknown. Microwaves couple well to hydrogen due to the 21 cm resonance line. Induction couples well to nickel as it is ferromagnetic. In either case, using a kitchen appliance for a power source is not practical if one is convinced that temperature of 1200 C is needed. There is plenty of evidence, going back to the early nineties (Thermacore) that high heat is not required, and decent thermal gain in Ni-H will be seen below the Curie point of nickel – so long as the power source remains efficient.
