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heat transfer

Posted: Sun Aug 20, 2017 6:21 pm
by monirh
Hey guys,

To start off it’s great to be on this forum and it’s going to be good talking to all you guys, also I had no idea where to post this so if it is in the wrong area let me know and I will move it.

what mode of heat transfer would be the most in the case of a fusor, between the plasma and outer environment? searching through the earlier post i could find not much reference to radiation heat transfer...wouldnt the temperature gradient is large enough for this to be significant.

Thanks

Re: heat transfer

Posted: Sun Aug 20, 2017 10:45 pm
by ian_krase
The grid is the part that gets heated the most -- you need to use a high melting point metal. Stainless works, tungsten is better (but hard to work with). The grid radiates heat to the chamber of the fusor, which also gets heated by plasma (but to a lesser extent relative to its size, so it doesn't get very hot).

Grids can be melted (this is sometimes a limiting factor on fusor current) and often glow red-hot. I was easily able to make the grid in my small demo fusor glow red.


The fusor chamber then dissipates heat to the air. A couple of particularly high powered fusors have water-cooled grids and/or outer chambers.


It's good to be able to heat the outer chamber of your fusor somewhat, because this helps with cleaning/degassing as you pump down, but too much and you start destroying O-rings, viewports, feedthroughs, etc, and anything that isn't sealed with Conflats.

Re: heat transfer

Posted: Mon Aug 21, 2017 4:57 pm
by Richard Hull
You mentioned radiation. What type? Nuclear? If nuclear, due to the particual radiation from the fusion process, (fusion energy), there is none!

Fusion energy.........

There is no fusion energy that you can collect per se. All of the real heat energy within the fusor assembly is due to net loss from the fusion process. Energy that is wasted. This is mostly due to ion bombardment, electron bombardment and failed neutrals slamming into the shell or body of the fusion chamber.

You will place over 400 watts into the fusor from the wall outlet via internal electrical demands and perhaps another 400 watts in the pumps and instrumentation to obtain and maintain the fusor's vacuum and monitor fusion.

The energy out of the fusor solely due to fusion is on the order of less that one microwatt. Thus, the net energy loss is about a billion to one. ( A billion times more energy is needed to do fusion than the actual fusion energy which is produced.)

Heat energy.........

As a heat engine, the fusor is a simple space heater that gets all of its interior and exterior heat from the wall outlet with all the attendent loss and efficiency of a common home space heater. (which is typically very high in efficiency)

Synopsis.........

There is no way, under any posssible circumstance or any application of artifice, that a fusor can produce net fusion energy that is....

1. collectable
2. convertable to usable energy, be it heat or electrical in form.
3. beome a useful source of nuclear energy

The best to be hoped for is that you can show that fusion is actually taking place. If you go the long haul route and boost the input, it can become a useful source of neutrons for simple activation and other amateur scientist experimentation projects. 95% of all successful fusioneers here never reached significant activation levels.

Richard Hull