Peter Davey Heater

[storre]

I suppose this is somewhat related to electrolysis though not exactly. On page 20 of this pdf (or search the pdf for "The Peter Davey Heater") they show a very fast liquid heater that uses the frequency of the mains (in this case 50Hz in NZ) to vibrate 2 bells (that naturally resonate at 50Hz due to their size). The distance between the bells is important also and the doc only describes it as a trial and error process by using the time it takes to heat water and gradually adjusting the distance between the bells. Says it uses cavitation and is said to have a COP of 20!

Using 2 bells tuned to the same frequency seems an effective way to adjust the distance between the bells to find the sweet spot. Especially if the bells are more of a flat sphere.

Haven't been able to find any more specific plans but with some trial and error it doesn't seem to difficult to reproduce. I've seen video of it working and it boils the water in seconds using very little energy since there is not a direct connection between the neutral and main.

[gyulasun]

The direct connection is made by the water itself and only a correct current meter can tell you how much input power is actually used from the mains!  Tap water usually conducts electric current quite well (think of hair drier accidents in bathrooms!)

[gyulasun]

doubled, sorry

[storre]

Shouldn't you be able to read the resistance across the bells once they are in water or whatever liquid? Since this works with any liquid and different liquids conduct more or less then the energy consumed would coincide with the conductivity of the liquid. It might not even work on something like salt water. Especially with 220v. It seems the key to how this functions is matching the oscillation of the bells with the frequency of the mains or some octave of it and also control the space between the vibrating bells to create a type of cavitation effect. Maybe similar to how a water hammer works? I think a better shape than a bell would be a cone shape since you could vary the distance between the bells uniformly with 2 of the same exact size and frequency.

[gyulasun]

Shouldn't you be able to read the resistance across the bells once they are in water or whatever liquid? Since this works with any liquid and different liquids conduct more or less then the energy consumed would coincide with the conductivity of the liquid. It might not even work on something like salt water. Especially with 220v. It seems the key to how this functions is matching the oscillation of the bells with the frequency of the mains or some octave of it and also control the space between the vibrating bells to create a type of cavitation effect. Maybe similar to how a water hammer works? I think a better shape than a bell would be a cone shape since you could vary the distance between the bells uniformly with 2 of the same exact size and frequency.

Hi,

Yes I measured with a multimeter the electric resistance of a glass of normal tap water just out of curiosity and found values from 4-5kOhms to 20-30kOhms depending on how deeply I merged the measuring tips.   Obviously the surface area of the possible bells are bigger than the tips so the conductance improves and also the distance between them counts. And surely the conductance of the hot water also better than the cold one.  I agree on your cone shape (or the like) variants could be better.
I found a link with ongoing replication attempts:
http://www.energeticforum.com/renewable-energy/1414-daveys-water-heater.html

and here is another link in French with some efficiency calculations, though no exact resonance tuning was done:
http://freenrg.info/Sonettes_Davey/calcul_sonette.html   (and see the html pages here http://freenrg.info/Sonettes_Davey/ )

rgds,  Gyula