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Registered Member #3637
Joined: Fri Jan 21 2011, 11:07PM
Location: Buffalo, NY
Posts: 1068
You basically mean, create one plate on the outside of the tube, then have any voltage between the two travel through the vacuum? It sounds like it would work, but I don't know if it would, since they require contact between the two metals. I don't know if it's the contact, or the actual flow of electrons between the two that causes the Peltier effect.
Registered Member #2901
Joined: Thu Jun 03 2010, 01:25PM
Location:
Posts: 837
Well voltage doesn't travel, but electrons ... specifically the hottest electrons, it's the selective removal of the hottest electrons (which most easily emit from the hot surface) which causes the cooling.
In practice actually getting electrons to emit from the surface at room temperature or lower is not trivial though.
Registered Member #2901
Joined: Thu Jun 03 2010, 01:25PM
Location:
Posts: 837
Transporting the heat isn't really an issue for sub-ambient cooling ... a heat pump can simply put the evaporator directly on the heat source, a peltier likewise.
Registered Member #2901
Joined: Thu Jun 03 2010, 01:25PM
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Posts: 837
It's a triode structure, but not on the same scale.
You want the grid to be pretty close (sub micron) to the cathode to keep voltages down, some electrons are always going to go to the grid ... the higher the voltage the worse the efficiency. Also you want small tips (micron scale) preferably coated with something like calcium on the cathode to increase the electric field and electron emission and constrain the electron flow (so less hits the grid).
You'd need photolithography kit to make that ... so that limits the people who can make it to people like Jeri Ellsworth and people with access to commercial/academic clean rooms.
Registered Member #1643
Joined: Mon Aug 18 2008, 06:10PM
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Posts: 1039
Sucks, I never had the cooling or something for my peltier, I had the current and the voltage, but never got it to frost, my large 4" wide peltier. Even tried a mega 7x11x3 inch anodized heatsink.
Nice job though, I imagine you can run it with the frost on it, since snow is hard to conduct even at 2000V MOT power
Registered Member #509
Joined: Sat Feb 10 2007, 07:02AM
Location:
Posts: 329
Pinky's Brain wrote ...
It's a triode structure, but not on the same scale.
You want the grid to be pretty close (sub micron) to the cathode to keep voltages down, some electrons are always going to go to the grid ... the higher the voltage the worse the efficiency. Also you want small tips (micron scale) preferably coated with something like calcium on the cathode to increase the electric field and electron emission and constrain the electron flow (so less hits the grid).
You'd need photolithography kit to make that ... so that limits the people who can make it to people like Jeri Ellsworth and people with access to commercial/academic clean rooms.
whole lotta excitement way back when, but nothing new as far as I know of :-/
Registered Member #2901
Joined: Thu Jun 03 2010, 01:25PM
Location:
Posts: 837
That's a diode, the problem with the diode structure is that the cathode/anode gap has to be tiny (on the order of 10 nm) to get a strong enough electric field to rip electrons from the cathode without giving them too much energy when they get to the anode (at least at room temperature or below, if the temperature at the cathode is high enough to make thermionic emission possible without field enhancement things become a lot simpler ... high temperature thermionic coolers are old hat).
This has made actually manufacturing these devices rather hard (the spacers will be far far larger than the actual gap, they have to be to have any kind of thermal insulation).
PS. damn, not the first to think of using a triode :
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Extreme MOSFET cooling
