Does physics forbid such a device; a heat destroyer

Deeviant

Multiple times I have asked you if you simply meant that an object loses energy due to black-body radiation, and you have never said "yes that is what I meant", this threw my off course. With further reading, I now understand how you are using the term, and I agree is used correctly and that there is "thermal contact" between objects and space, but I am still completely baffled by your responses. A space ship is obviously always in thermal contact with space, it happens by default, and in the case, is to not nearly sufficient rate of heat loss, hence the whole idea of the thought experiment in which to create a process that has a faster rate of heat loss. Really, the term "thermal contact", though accurate, is really not helpful at all; speaking directly to black-body radiation rather that "thermal contact" immediately elicits the exact mechanism and even leads to easy finding of the exact mathematical description of the phenomenon (i.e. Planck's law of black-body radiation).

I think the main problem that I have digesting the rather consistent feedback from you guys is that objects already do what I what I want to accomplish here(albeit I want to accelerate the process somehow within the rules the universe has laid out): all objects turn their heat into electromagnetic energy and cast it out into space. It is trivially easy to see then, that converting heat(or whatever you would like to call it) into electromagnetic energy(in this case with 100% efficiency with no outside energy) does not break any laws of physics, this happens everyday; as you read this you are literally using converted heat energy that was converted into electromagnetic energy from the sun. So the cooling of an object by converting it's heat energy into electromagnetic energy without using additional energy is not against the laws of physics, it just isn't, if it was, we wouldn't be here right now.

TobyC

Deep space isn't a perfect vacuum, I think I read somewhere that even in inter-galactic space there is about one hydrogen atom per cubic metre, and it therefore has a temperature associated with it from that.

Then of course it also has quite a bit of radiation in it, cosmic microwave background and light from stars, and you can associate a temperature to that as well, which should end up being the same temperature that the hydrogen gas is at. If you could get a machine which transferred heat from a system to the hydrogen gas for example, then that would be a way of cooling anything down to whatever the temperature of deep space is without having to put any energy in.

TobyC

It's true that the energy we use comes from the sun, but it isn't converted from heat to work at no cost. The sun's radiation is at a higher temperature than the Earth, and that is what allows the conversion to happen, you always need a cooler reservoir if you want to convert heat to work, and your post made it sound like you wanted to build your machine without a cooler reservoir.

It now sounds like you want to place your machine on a spaceship in deep space, I didn't realise that before, in which case it is much easier to see how you could put things in contact with space to cool them down. In fact, that will happen anyway. If you have a spaceship in inter-galactic space, I imagine the problem will not be cooling stuff down, but rather keeping yourself warm. If you are within the solar system though you have to be more careful because then radiation from the sun is at quite a high temperature and your ship will absorb that.

No, it is really against the law of physics, it just is. You have to be careful what you mean by electromagnetic energy though, electromagnetic energy can still be heat energy, as people have pointed out. But either way, you still can't do it for free. If the electromagnetic energy you're getting out is in the form of heat then you can do it but there needs to be a colder reservoir to dump the electromagnetic heat energy in. And if you want all of the electromagnetic energy in a form you can get work from, like the form that could power a computer, then you just can't do it at all.

Some of the language here is getting confusing but I'll try to be clear what I am saying: "It is impossible to build a refrigerator that does not need to be powered".

DaleSpam

It is not just radiating blackbody radiation to space, it is also receiving blackbody radiation from space. That is why the phrase "thermal contact" is used rather than "losing energy due to blackbody radiation". It misses the other half of the physics (besides being wordy).

In any case, I was very clear even back in post 10 that the mechanism of heat transfer was via radiation. If you had spent less time telling me that I was wrong and making me repeat and re-justify my statements then maybe you would have cleared up your confusion faster. You act as though I have been the impediment to communication when, in fact, it is your continued desire to correct me and tell me what I am doing wrong that slows communication by making me waste time defending my statements rather than helping you learn. This post is another great example.

Deeviant

The 2.7k is inconsequential, it might as well be absolute zero for the purposes of a mechanism trying to dump the heat from a fusion reactor, it's a rounding error; it is pedantic.

I still would like to know why if I take what is being said in this thread to heart, I would have to conclude my very existence is barred by physics. I asked if it was possible to convert heat energy into some other form, without using any additional energy and further more if such a mechanism could be used to cool an object; the resounding answer is: no it violates physics. If it violates physics, why does it happen today, right now, in a absolutely massive scale?

Muphrid

Just what is it that you think converts heat energy into another form without taking energy to do so?

TobyC

You can remove heat from a system (and possibly convert it to some other useful form) but then one of two things has to happen:

1) You put more energy in by doing work to power it (like how a fridge works).

2) You have a colder reservoir handy to dump some heat in (like how putting an ice pack on something, or a car engine, or a fusion reactor works).

If the surroundings of a car were the same temperature as its engine then it couldn't work.

Nothing going on in the universe today violates this rule as far as we know. What examples were you thinking of?

DaleSpam

Nobody ever said that. We said that you could do that, it is called a heat engine, it requires a cold reservoir, and the efficiency is limited by the Carnot efficiency limit. Heat engines don't violate physics and they happen on an absolutely massive scale.

Deeviant

Single reservoir: The Sun, which has for the purposes of this example a "single temperature". The sun's heat is converted directly into em radiation , the photon travels from then sun to the earth then strikes a solar panel knocking an electron into the conduction band and creating current, the current does some work. No outside sources of energy were used. No laws were violated. The heat energy was converted directly into another type of energy, and in this cause, did do work.

TobyC

The solar panel is at a lower temperature than the sun, that's why it works. The solar panel is the second reservoir. If the solar panel was at the same temperature as the sun it wouldn't work. In any example you come up with you'll find there is always some object in there which has a lower temperature than what you're extracting heat from, and that is crucial, unless you want to put energy in to power it.

The solar panel isn't actually essential in that particular example, heat is being removed from the sun as radiation whether the solar panel is there or not, just not as useful work, it stays as heat. In that case though the second reservoir is space, filled with hydrogen and an EM field at a very low temperature.

Whovian

Yes, but (I think) this relies on the solar panel being "cooler" than the Sun.

DaleSpam

You do realize that the solar panel is colder than the sun, the hot sun transfers thermal energy to the cold panels, and the efficiency is much lower than the Carnot limit, right? This is a great example of a heat engine.

Deeviant

First of all, let me thank everybody here for providing valuable insight and taking time to contribute to this thread, I do very much appreciate it.


And now I will jump back into it,

Even if such a process followed Carnot efficiency laws, it has absolutely no bearing on the first question: can heat be converted into another form of energy and thus be effectively purge heat from a system without some proportional outside energy being used.

So, the original question is can an object be cooled by converting it's heat into another form of energy, without the need to spend energy for the conversion, and can this be done to cool it down to some lower limit. The consensus was that it could not; that it was against the rules of physics, except that this is exactly what an object does all by itself when left by it's own accord in space: a object will convert all of it's internal energy into electromagnetic energy, cooling itself off to some lower limit(in this case stasis with the background radiation).

So I guess the question as it currently stands is not: can thermal energy be removed from an object without expending energy, as this is a foregone conclusion via black-body; but if physics really does some bar it from somehow artificially increasing the rate in which this happens. One trivial way to do this is to simply increase the surface area of object, but is that the only way.

Drakkith

I don't think the issue is in converting heat to EM energy, it is converting that EM energy to work that is the issue.

DaleSpam

No, the consensus was that converting heat to another form of energy is what a heat engine does, that it requires thermal contact with a cold reservoir (like deep space), the lower limit is the temperature of the cold reservoir, and that the efficiency is limited by the Carnot efficiency.

Where do you think anyone has said otherwise?

Deeviant

In thermodynamics, a heat engine is a system that performs the conversion of heat or thermal energy to mechanical work

A heat engine coverts thermal energy to mechanical work. It is simply wrong to continue to insist anything to do with thermal energy is a heat engine. Especially since in this case ending up with usable work is not at all required. Even if we did want to do work, who cares, the primary concern is to dump the heat and whatever work we get out of it is icing on the cake. I repeat, the question here is how quickly and efficiently does physics allow us to remove heat from an object. Nature has already provided us with a perfect example via black-body radiation, but does physics bar anything faster and more efficient.

As far as you're question, it is has been stated earlier in this thread that in order to pull heat out of mass, one must expend outside energy, this is false. Another claim was that pulling heat out of an object and converting into electromagnetic energy violates entropy laws, this is also false, black-body radiation does this already. Other statements insist that Carnot efficiency has something to do with the fundamental question I posed(I admit even I mentioned it in my OP), but as this discussion has progressed, it is now obvious that Carnot efficiency has nothing to do with it.

The question is, is a theoretical method to convert heat into EM in a method similar to black body radiation but faster.

Drakkith

There is no machine that can take thermal energy and convert it into another form of energy without losses. A simple object emitting black body radiation is not a machine.

Sure. You can use energy and pump the heat from one location to another, with the end location being hotter than the source. Otherwise I don't believe you can make it any faster without expending energy.