🧵 Carnot efficiency is a tax
Anonymous at Mon, 20 May 2024 17:52:45 UTC No. 16184778
This contraption should keep both radiators in thermal equilibrium.
Both radiators emit same power of light. Light concentrator intensifies the 112kW of light beam from the low temp radiator with an area of 1m^2, down to an area of 0.0625m^2. Light from the high temp radiator makes the return trip (reversable paths), going from 0.0625m^2 diluted over 1m^2. The light concentrator ensures both radiators are in equilibrium:
112kW is emited from both radiators, there is 224kW flux of light passing through the light tube. Both radiators emit and receive 112kW to and from their partner. There can be no change in either radiators temperature.
The key element of this set up is the "light concentration. Assume briefly such a thing could be made, would the rest of it work?
Anonymous at Mon, 20 May 2024 18:16:11 UTC No. 16184805
>>16184778
If you assume that it would work then it works yes
Anonymous at Mon, 20 May 2024 18:31:51 UTC No. 16184831
I don't understand what is the purpose of this device. I can keep bacon and icecream in thermal equilibrium and?
Anonymous at Mon, 20 May 2024 19:18:04 UTC No. 16184920
>>16184805
How would I go about making a "light concentrator" in practice?
Suppose we use a big magnifying glass to intensify the light from the larger cold radiator onto the small one.
However, people have raised objections on "light concentrators" due to " conservation of etendue"
https://en.wikipedia.org/wiki/Etend
Supposedly you can't concentrate light into a spot brighter than it's source using a lens. I don't understand how this could be the case, as I can imagine a series of mirrors or optical cables which subvert this problem.
If anyone could explain if this "conservation of etendue" would stop me using optical cables/mirrors to focus the light that would be appreciated.
The next objection usually raised after finding no objections to using optical cables to focus the light is destructive interference magically cancelling out the perfect amount of light to prevent the OP picture being true.
Anonymous at Mon, 20 May 2024 19:26:11 UTC No. 16184932
>>16184831
Assuming a "light collector" could be built, exploiting this effect to extract more than Carnot efficiency allows for.
The OP picture shows the system in paradoxical equilibrium. If you increased the temperatrue of the cold side radiator, it would start emitting slightly more than 112kW of light.
An imbalance of radiation is formed, as the hot side radiator is still emitting 112kW, but receiving 112+n kW of light, so it starts to heat up.
By connecting a heat engine between both radiators, heat from the hot side radiator flows through the heat engine to the cold side radiator generating work.
Sorry I'm not explaining it well.
The only relevant thing I see is this "light concentrator". If one could be built, I don't see why this wouldn't work.
I'm not making free energy, only converting with 100% efficiency what's put into the system
Anonymous at Mon, 20 May 2024 19:51:24 UTC No. 16184973
>>16184920
It's got nothing to do with brightness. With your purpose in mind one can express this like such: You can not heat an object using radiation to a higher temperature than the source of the radiation itself, regardless of how much you focus the radiation. This should be fairly self evident. A photon will not be able to add energy to an object hot enough to emit such photon. Idk why its always the people most unedicated in a certain field that come up with the most outlandish concepts on /sci/.
Anonymous at Mon, 20 May 2024 20:25:25 UTC No. 16185017
>>16184973
>You can not heat an object using radiation to a higher temperature than the source of the radiation itself
Ah, but how can lasers heat up objects to temps far greater than their own.
>A photon will not be able to add energy to an object hot enough to emit such photon.
I think what you're saying here is that for a given temp, a black body will radiate a particular frequency of light, or band of spectrum of light.
The issue there is that very tiny amounts of high frequency light are emitted by lower temperature BBs.
Anonymous at Mon, 20 May 2024 20:27:26 UTC No. 16185021
>>16184973
Putting it another way, the thing that dictates the temperature a black body will be heated to by incident light is either:
The intensity of the light. (what I understand to be so)
Or special quality of the light. (frequency?)
Anonymous at Mon, 20 May 2024 22:57:08 UTC No. 16185238
>>16184973
Anyone got a better answer than this? He's just stating OP diagram wouldn't work because it wouldn't.
Anonymous at Mon, 20 May 2024 23:11:42 UTC No. 16185259
>>16184973
>It's got nothing to do with brightness. With your purpose in mind one can express this like such: You can not heat an object using radiation to a higher temperature than the source of the radiation itself.
Off the bat that's wrong.
You can melt wax and boil water with powerful antenna radio wave sources.
>>16184973
>A photon will not be able to add energy to an object hot enough to emit such photon. Idk why its always the people most unedicated in a certain field that come up with the most outlandish concepts on /sci/.
Speak for yourself anon.
It's almost as if you've never heard of microwaves. Emitted by black bodies at 1 Kelvin yet capable of melting glass and metals at 1500 Kelvin.
Anonymous at Mon, 20 May 2024 23:16:21 UTC No. 16185266
>>16184932
>I'm not making free energy, only converting with 100% efficiency what's put into the system
Which isn't possible. It's a pointless question and proposition. I don't know why you're even mentioning it.
Anonymous at Tue, 21 May 2024 01:10:15 UTC No. 16185404
>>16185266
>Which isn't possible.
Why not given this system? Problem with 2nd thermo law is people say "X doesn't work because of the 2nd law". When they should be saying "X doesn't work due to Y, hence the 2nd law is observed".
TLDR why won't my machine work?
Similar sounding problem (long since solved) is "the Ellipse paradox":
this paper goes over why it's not a problem
https://www.researchgate.net/public