Timeline for If air is a bad conductor, how does fire heat up a room?
Current License: CC BY-SA 4.0
12 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| S Jun 30, 2021 at 19:32 | history | suggested | Ben | CC BY-SA 4.0 |
typo: you -> your, grammar: belonging to -> at
|
| Jun 30, 2021 at 19:03 | review | Suggested edits | |||
| S Jun 30, 2021 at 19:32 | |||||
| Jun 30, 2021 at 17:32 | comment | added | 5th decile | This is not some mere detail as some contributors here seem to suggest: if the radiation is not in thermal equilibrium, Wien's displacement law is not necessarily valid to relate frequency of dominant radiation to temperature. Also, the power from the outgoing radiation doesn't simply follow the Planck $T^4$-law nor is it specifically proportional to some surface area of the fire. I think that point is very recognisable: upon refueling a fire it can suddenly radiate much more intensely without that its surface area has grown significantly. | |
| Jun 30, 2021 at 17:13 | comment | added | 5th decile | I did some googling and my conviction has turned farther away from the "campfire -> mainly blackbody spectrum" hypothesis: ProfRob's answer here physics.stackexchange.com/questions/648273/… and the reference paper in his answer seems to settle the question: chemistry is (as expected) a dominant factor in the colors of a woodland fire. | |
| Jun 29, 2021 at 9:59 | comment | added | AnoE | I find it very confusing why there is so much talk about black body radiation here. The term is "(thermal) electromagnetic radiation". Black body is a tiny part of that, and a theoretical construct at that. Since OP is obviously quite new to thinking in these terms, I would find it much more useful to introduce them to the concept of electromagnetic radiation in general (i.e., that the same thing that we perceive as light, or which allows us to transmit radio signals, also is a direct energy transport mechanism if intensity becomes higher). | |
| Jun 29, 2021 at 0:03 | comment | added | gardenhead | Could just replace "blackbody radiation" with "thermal radiation" to avoid having to worry about whether a fire (or the room for that matter) actually produces a black-body spectrum. | |
| Jun 28, 2021 at 20:54 | comment | added | JimmyJames | In my experience, fire produces more radiant heat once it goes to coals. For example, if you want to cook on a camp fire, you should wait until it burns down. At that point, would the radiant heat still primarily be from hot gases or could the hot coals (carbon) also be radiating at that point? | |
| Jun 28, 2021 at 14:38 | comment | added | my2cts | @ThibautDemaerel Perhaps you assume that the chemical reactions are radiative, but they are not. They produce hot gasses, which emit black body radiation. | |
| Jun 28, 2021 at 14:10 | comment | added | 5th decile | Do you have any evidence that a bonfire emits a black-body spectrum? This is not to be expected since this radiation comes from a irreversible chemical reaction, i.e. the bonfire is far from thermal equilibrium. Mechanically, the radiation is not allowed to scatter or interact sufficiently with the environment before hitting your eye. | |
| Jun 28, 2021 at 9:14 | history | edited | my2cts | CC BY-SA 4.0 |
added 19 characters in body
|
| Jun 28, 2021 at 9:08 | comment | added | Poseidaan | I think it would be better to use Kelvin in this answer. Otherwise the scaling with $T^4$ might be misinterpreted. The ratio of power emitted by fire compared to air is approximately $\left(\frac{800 K}{300 K}\right)^4 \approx 50$, not $\left(\frac{600 C}{20 C}\right)^4 \approx 800000$. | |
| Jun 27, 2021 at 17:46 | history | answered | my2cts | CC BY-SA 4.0 |