A question about fusion

originally posted by: Rethaya
I guess having a reactor in space might make dealing with any cooling issues easier. We could just redirect the waste heat that we don't need for power to the dark-side of the reactor, somehow.

Actually, it makes cooling issues harder by far. In space, you can only dump the heat by radiation.

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originally posted by: MerkabaMeditation
if we used a pool of water like traditional nuclear sites to contain the energy then would the water not evaporate immediately at these extreme temperatures?
-MM

Answer: don't confuse temperature with heat. It's tough for the layman, though.

originally posted by: Bedlam

originally posted by: MerkabaMeditation
if we used a pool of water like traditional nuclear sites to contain the energy then would the water not evaporate immediately at these extreme temperatures?
-MM

Answer: don't confuse temperature with heat. It's tough for the layman, though.

Frankely, I find your "answer" insulting as you insinuate that us "laymen" would not understand the difference between temperature with heat as you would and that is your answer; you would look much better if you attempted to explain the difference instead of coming with such an elitist answer. And, who said that I'm "confused"? You seem to suppose that I would not understand the difference between temperature and heat and that your "answer" (which is just a statement using two quite insulting words "confused" and "layman") should suffice based on some kind of merit which I suppose is your ATS score(?).

Well, here is a follow-up question from a "layman" to someone as intellectually superior as yourself ; if you place a red hot iron into a bucket of water it almost explodes and that iron is less than 1,000 degrees, so I'm guessing that 4 million degrees would completely evaporate any water in an instance. Is this little layman wrong?

-MM

originally posted by: MerkabaMeditation

originally posted by: Bedlam

originally posted by: MerkabaMeditation
if we used a pool of water like traditional nuclear sites to contain the energy then would the water not evaporate immediately at these extreme temperatures?
-MM

Answer: don't confuse temperature with heat. It's tough for the layman, though.

Frankely, I find your "answer" insulting as you insinuate that us "laymen" would not understand the difference between temperature with heat as you would and that is your answer;

No, it's that laymen may often have imprecise notions. That's OK, and he was letting people be aware of that.

you would look much better if you attempted to explain the difference instead of coming with such an elitist answer.

lmgtfy.com...

a reply to: mbkennel

A "Let me Google that for you" link, how very immature.

-MM

originally posted by: MerkabaMeditation

Well, here is a follow-up question from a "layman" to someone as intellectually superior as yourself ; if you place a red hot iron into a bucket of water it almost explodes and that iron is less than 1,000 degrees, so I'm guessing that 4 million degrees would completely evaporate any water in an instance. Is this little layman wrong?

-MM

It depends on the difference between temperature and heat.


What happens depends on how much iron there is there, which relates to the difference between temperature and heat. A few femtograms, at 4 million degrees isn't going to boil all the water in a bucket, but a kilogram would.

www.spitzer.caltech.edu...

originally posted by: Rethaya

originally posted by: Maverick7
Where we're making the mistake is trying to build it on Earth (beyond a model), and finding containment a major issue.

I guess having a reactor in space might make dealing with any cooling issues easier. We could just redirect the waste heat that we don't need for power to the dark-side of the reactor, somehow.

Now which side would that be? And if there were such a thing, what happens to it after you redirect the waste heat to it?

originally posted by: MerkabaMeditation

You seem to suppose that I would not understand the difference between temperature and heat...

Well, that assumption is based on your OP, frankly.

Without copypasta, can you tell me the difference? It's the answer to your question.

Most people that do not study science DO confuse temperature and heat, the way they confuse power and energy, or speed and acceleration.

originally posted by: MerkabaMeditation
Well, here is a follow-up question from a "layman" to someone as intellectually superior as yourself ; if you place a red hot iron into a bucket of water it almost explodes and that iron is less than 1,000 degrees, so I'm guessing that 4 million degrees would completely evaporate any water in an instance. Is this little layman wrong?

-MM

Even in THAT question, you're conflating heat and temperature.

When you sort that out, you will answer your own question, and understand my response.

How about this...which contains more heat, a white hot needle, or a bathtub full of lukewarm water?

originally posted by: MerkabaMeditation
... you would look much better if you attempted to explain the difference instead of coming with such an elitist answer.

...should suffice based on some kind of merit which I suppose is your ATS score(?).

If you consider "elitist" and "some kind of merit" to be "took second semester freshman physics" then I suppose I'm guilty as charged. At least I *think* it was second semester. Might have been first.

Seriously, though, confusing temperature and heat is the reason you are having issues with this. A lot of people do, though.

Thinking about it some more, the smallest 'sun' we would be able to ignite would be about 0.07-08 solar masses. So you create one, find one and tow it there, or IDK, ignite one of the gas giants by adding mass?

It would have to be probably 10x the distance of the Moon, 2-3 million miles out. Surround it with a set of dyson spheres, or advanced concentric solar panels ( ( o ) ), so that the entire output is captured then transmitted somehow to be used on Earth as electric power. Same way solar power is, but maybe find a wireless method? Tunneling (lol)?

Then you'd not be dealing with size issues, containment, or accidents. That 'system' would have enough gravity to support fusion but not so much it would affect tides, or perturb orbits.

Something to consider.

Interesting replies. If course, I knew about magnetic containment fields/tokamaks but never questioned how they would use the heat generated to boil the water and run the turbines.

I guess they still have at least 10 years to figure it out.

originally posted by: Bedlam

originally posted by: MerkabaMeditation
... you would look much better if you attempted to explain the difference instead of coming with such an elitist answer.

...should suffice based on some kind of merit which I suppose is your ATS score(?).

If you consider "elitist" and "some kind of merit" to be "took second semester freshman physics" then I suppose I'm guilty as charged. At least I *think* it was second semester. Might have been first.

Seriously, though, confusing temperature and heat is the reason you are having issues with this. A lot of people do, though.

Yes. It's a common confusion. I was trying to explain to my wife why its not cold in space..but she wasn't getting it.

a reply to: Bedlam

At 4 million degrees even metals evaporate - regardless if there is 1 gram or 1 kilo. My question is regarding how can we extract any kind of energy from 4 million degrees when all elements that it touches instantly evaporates.

-MM

a reply to: MerkabaMeditation

My question is regarding how can we extract any kind of energy from 4 million degrees when all elements that it touches instantly evaporates.

That's going to depend on the quantity of heat (BTUs for example), not the quality (temperature).

I hear a pistol shrimp creates a bubble in the water that implodes, releasing energy at the temperature of the Sun. Note the oceans haven't boiled away. High temp but small amount of heat.

originally posted by: MerkabaMeditation
a reply to: Bedlam

At 4 million degrees even metals evaporate - regardless if there is 1 gram or 1 kilo.

-MM

Heat. Temperature. They are not the same thing.

Enthalpy = mst
a reply to: MerkabaMeditation

a reply to: MerkabaMeditation
MM, I will try to give a better and more detailed explanation to your confusion (see, made a pun!)

The density of plasma is the key. See with fusion you use really light particles instead of fission where you use heavy particles. This is akin to the novelty plasma globes. They heat up to thousand of degrees but the density is so low that when you rub your fingers over the surface you do not get burned. Same with a plasma TV.

Back in fusion reactor world, the temps are around 100 million degrees Celsius for Deuterium-Tritium fusion. These two gasses combine under magnetic pressure. Remember the old equation PV = T?? P is pressure, V is volume, and T is temp. When you have a controlled Volume the only variables that can change are P and T (V = T/P). As you use super-cooled magnets to apply pressure, the temperature rises but not enough. So you add heat to the system (microwaves are typical) to create the conditions for fusion. All of this in a magnetically confined gas/plasma that is not touching the containment vessel.

The gasses fuse together to create Helium and a super energetic neutrino. At fusion temps tens of thousands of neutrinos go zipping all over the place per second. Inside your fusion device you have a lithium blanket. This blanket "absorbs" the neutrino creating another tritium particle. The neutrino also vibrates the blanket (i.e., it adds heat). This process also imparts a little radiation to the blanket and containment vessel. The blanket heats up. Around the blanket is the containment vessel that you rinse with water (or glycol or any heat tolerant liquid) as a coolant which in turn heats up because the heat "moves" from the blanket toward the cooler substance (surrounding coolant) trying to reach equilibrium. But this liquid coolant does not stay put it is shot off to a heat exchange unit.

See, if you ever made beer you would get this idea. After boiling the wort (the sugars that come from grains that you feed to yeast to make beer) with all the hops added you cool the boiling liquid using a heat-exchange unit. In the case of wort, you can use a copper coil pipe submerged in the wort and run cold water through it. The 2nd law of thermodynamics takes over and cools your unfermented beer while hot water leaves the drain hose and down the drain--or buckets to wash your car, floor, or any other greener use. This is pretty quick. You can cool 5 gallons of wort with just a normal garden hose and immersion coil in less than 10 minutes--from boiling.

In the case of the fusion device, the heated water from the heat-exchange unit is used to turn a turbine. The now cooled liquid coolant (it "exchanged" its heat with the water) is recirculated back to the fusion device to be re-used.

Here is a good link with pictures that will explain the word salad above. Source: Science - How Stuff Works Link:How stuff work: fusion reactor pg. 4

So now what? You have a fusion device with super-cooled magnets, more tritium being magnetically confined with the plasma, and helium gas. You draw away the helium using charged plates that the plasma ignores. Now you simply dump a little more deuterium in and hit it with a microwave thus adding heat to the system. Rinse and repeat. And you do that until you use up your lithium blanket or the containment vessel is irradiated. Then you swap those out, test, cool, and start back up.

See no touching of the plasma is done. No metal plates that might burn up. Etc.

A nice little trick to remember about "heat vs temperature" is this. When you are standing there with the door open to the outside does your mum yell, "what! Close the door! Are you trying to heat up the outdoors" or "What! Close the door! Are you trying to temperature up the outdoors"?

Does that help?

[ETA: Hope I didn't muss it up with the 2nd law of TD! Hope the beer story helps out too!]