the incredibly simple, cheap, sturdy friction heater.

[jadaro2600]

I think a better solution may be to use an outer pan assembly, and an inner flap assembly where the flaps are made of sheet metal and centrifugal force causes them to contact the outer pan.  Oil may then be used to lubricate the system, filled, the outer pan would radiate heat and the oil would retain it.  A fan operating in the high setting would cause maximum contact, medium would be minimal and low would be none, in low setting, the fan would be radiating pre-existing heat.  other settings would be used to generate and radiate heat.

[ATT]

I think a better solution may be to use...an inner flap assembly where the flaps are made of sheet metal and centrifugal force causes them to contact the outer pan.

I think heat generation through paddle agitation was demonstrated before either Frenelle/Pickens or cavitation as used by Hydrodynamics Inc.

The question, in all three cases, is which of these requires the least energy input for a given amount of heat output.

Just from observation, the paddle method looks like it would require more power due to the increased surface area that is in contact with the fluid medium.

That isn't to say it would necessarily be less efficient, it might produce more heat because of that increased surface contact, too.

An A-B test using the same container-dimensions and each of the three internal agitation methods might show the most effective combination.

Again, just by way of observation, wouldn't increasing the RPM also subject the paddles shown in your diagram to more resistence from the working fluid, thereby keeping them from expanding tword rim of the container they're spinning in?

You might be able to test this by attaching sheet-metal pieces to a drill bit and spinning them (using a -BATTERY- drill-motor) in a container of water, which is much less viscous than oil, just to see what the effect would be with a load on the paddles.

(Be careful! If using water, DON'T try this with a mains-connected AC drill-motor!)

Then too, once you get the fluid spinning, it might not present the same impediment to your flaps as when you first started the spin.

I'm guessing you'd have some vortices coming off the ends of your flaps as they rotated, too, so that might also keep you from expanding out all the way.

You have a good idea to try though.
.

[Foggy-Notion]

The most efficient method is the smooth bore 1/8" oil gap,
you could spin it all night with gears and a hanging weight.
A wider diameter will work at speeds as low as 70 RPM.

[jadaro2600]

The most efficient method is the smooth bore 1/8" oil gap,
you could spin it all night with gears and a hanging weight.
A wider diameter will work at speeds as low as 70 RPM.

Wouldnd't it be easier to just bore wholes in it like a cavitation heater... you could even use sheet metals and a ball-ended stamp to create indentations.  Come to think of it, I have the tools to do this, I might as well try it.  I could make the rotor out of sheet metal and fill it with plaster, the stuff seems strong enough.

[Doug1]

Fog
  Stainless steel dog watering bowls with a plate to fill the extra gap in the bottom because it will be more then 1/8th gap in the bottom. A bearing from a roller blade wheel or skate board wheel for the center. May need holes in the bottom if the oil slings out of the two bowls to let it circulate back between the two bowls. If it proves to be worth playing with further make the bowls counter rotate to increase speed between the two bowls with out using a faster motor.
   One central shaft can turn a counter shaft if the counter shaft is  sml tube fit over the central shaft with a friction wheel to a short axle with another friction wheel touching the outer shaft for the opposite bowl.
   Dog bowls are cheap and easy to work with. Some of them are pretty large. Chances are you can put that together with out much more then some pocket change a crying child and a pissed off dog.