Vaporization of Metals: Electric Current & Boiling Points

[axi0m]

If one were to take a powerful source of electricity, such as a bank of high-voltage electrolytic capacitors, and short the source across a thin length of metal wire, the wire would "vaporize."

My question, is what is actually happening to this wire? If it were a very thin strand of aluminum, for example, being that aluminum's boiling point is 4,566 degrees F, would the wire actually be transitioning from a solid to a gas, thus giving off a large volume of aluminum gas, or vapor?

 

[Mapes]

Aluminum gas and aluminum liquid, I would think. Aluminum liquid is electrically conductive, so for an instant there would be a strand of liquid continuing to heat from the applied current. Once this strand was broken up via boiling, though, there would be no driving force for continued heating.

 

[axi0m]

The objective of the experiment is to propel a projectile via pressurization. It seems that water is very effective at these types of things, hence its use in steam locomotives and nuclear power plants for converting heat to work. Being that it turns to gas at a lower temperature than the conductive metal itself, it seems that the best method to create a high pressure would be would be to pass as much current as possible through a metal that has as high of a boiling point as possible, thus providing the highest amount of heat to the water.

For the first experiment, then, I will try different configurations of tungsten wire through a chamber of water. The power source is currently 10 6800uF 450V electrolytic capacitors.

 

[Mapes]

Do you need to provide multiple bursts (an in an inkjet head, for example), or is this a one-time effect?

You may be interested in the maximum power theorem, which says the maximum power will be transferred to the water when the immersed conductor has the same resistance as the rest of the circuit combined.

 

[axi0m]

It will be a single event. Thank you for bringing that to my attention. I wonder which allows me to provide the highest kinetic energy to the projectile, the load resistance that provides the greatest power or the load resistance that provides the greatest efficiency?

 

[Mapes]

Well, if you define efficiency as kinetic energy per unit input power, for example, it would likely be the same thing.