Andreaerdna
If God is the answer, then the question is wrong
Dominant at what?[/QUOTE said:
oups, I did a mess with quote
Thermal Radiation Discussion
- Thread starter natural farmer
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oups, I did a mess with quote
i have seen this comment several times now but i sure don't understand this ... i set my Nichrome wire heater to 385f, say, and a draw can change ambient air into 385F air ... this is with a heater having 2.0099 sq in of surface area, not counting the heat reservoir at the bottom of the oven tube - (a unique feature i might add and definitely in the patent application).
i just chalk it up to designer's choice.
one other comment ... it's the trichomes we're trying to heat up, not the herb. wax does conduct heat, i guess, since it melts.
Andreaerdna
If God is the answer, then the question is wrong
I agree 100%. Dominate in a particular design feature in the vaporization process is how to categorize vapes.
- Conduction Vape: When herb is touching hot oven walls we can safely call it conduction. Though the heat is also moving through the load in other ways than just conduction. Conduction is the transfer of heat through a solid (or fluid) to another solid. Metal is a great example of a conductor and can transfer a great deal of heat because of the free electrons within metals that vibrate very fast. When heat is applied these electrons vibrate so fast they cause the atoms to vibrate which produces heat.
- Beyond that we seem to be getting into endless mental masturbation just like my post above.
that being said there is NO CONDUCTION possible between a hot metal and a vegetal in contact with it. even between two metal bar side by side, it must be the same body in order to "share" atomic vibrations and conduct heat.
conduction is the way heat flow, spread INSIDE A BODY, is the explanation why while torching the tip of a nail we can be burned keeping the other side of the nail, far away from direct radiation of the flame. but it is the heat radiation from the evenly hot nail burning us, not heat conduction. is it clear enough, my english isn't always clear
hot metal heat by radiation and ONLY by radiation the vegetal touching it which at his time start getting evenly heated by conduction inside it (a lot slower than metal) and this second step happens also in "pure convection vape". the difference, maybe, is that radiation is slow heat carrier (as OF said) and continue cooking while not hitting and convection has often massive heat transfer and cook only on demand keeping a fresher taste.
Andreaerdna
If God is the answer, then the question is wrong
I agree only vacuum does not conduct heat but heat conduction isn't heat transfert. they seems alike but they are not synonymous in physics.
there is a definition I take from wiki that explains what does means heat conduction and it is not related to more than a body, conduction is confined in the body where it takes place, to spread out of a body heat need convection or radiation.
there is a definition I take from wiki that explains what does means heat conduction and it is not related to more than a body, conduction is confined in the body where it takes place, to spread out of a body heat need convection or radiation.
This thread needs a bump.
Keywords: IR radiation, thermal conduction, forced convection, natural convection, thermal conductivity list, list2
Keywords: IR radiation, thermal conduction, forced convection, natural convection, thermal conductivity list, list2
Great demonstration, and explanation 
Perfect vape for the job too 
Good info there...Andreaerdna
If God is the answer, then the question is wrong
I have no problem with that.
There is conduction insides each fragment of material, heated by radiation (that how conduction heat). The same with convection: heated air heat the external of each fragment and then conduction happens (that explain how a whole nugg can be vaped in enano or other 100% or near convection device like hammer or vaponic but not as well in a radiation device like VM or MFLB - I mean convective heated air is more effective and sourround better the nugg than radiation (shadows).
Difference between radiative VM and convetive Enano or Lotus is the heat source being all around the load (in order to be effective) so preheating of the bowl start to cook material before hitting and after (that explain faster degradation of grassy taste) while with convective you get all the vaporized material you produce
OF
Well-Known Member
OK, folks, I've just been pointed back to this thread by the above post. The discussion there started as 'how did we manage to do what you can't do (get near immediate vapor from a cold Vapman' post by Rene (the maker), he said very light load, very dry were the keys. I responded 'this makes sense, less herb to heat means less time to transfer the needed energy to make 400F or so with some of it. By conduction. That got me called out on 'you know it's really radiation'. For the record I believe VM to be a basically a conduction vape, basically no radiation when making vapor, because radiation only works if the source (hot part) is much hotter than the load (our herb). If you follow the above link for that posted above you'll find my listing a post where the maker (Rene) confirmed this point. No matter how much you might think otherwise, no radiation heat transfer (not to be confused with heat 'radiating out' from it's source.
http://fuckcombustion.com/threads/vapman.94/page-83#post-737930
The vaulted 'oven proof' above fails because I'll maintain the glowing red part is this temperature difference. Cool the heater off and the food slows down then stops cooking? Since, in this analogy, the hottest part of the oven is only a few degrees hotter than the holiday turkey, how many hours per pound do you figure by radiation?
I understand this is a very tough concept for many of us. As adults we learn calculus by understanding algebra which we learn by understanding 'addition, subtraction, multiplication and division' after we lean number systems after we learn to count. That's not meant as a slight on anyone, only pointing that truly understanding Thermodynamics needs a strong base in physics for most if not all of us. This means entropy and enthalpy raising their ugly heads in order to get a grasp on what 'heat transfer' means.
I'm confident I'm on solid ground, in fact I used to get paid to try my best to teach this sorta stuff. But I'm retired now, and nobody's paying me anymore and I really came here to talk vapes and help folks if I can......and in a small corner of portables at that. I also think Rene's agreeing with my 'radiation is only useful if there's a very large temperature difference' shows he went to the same sort of schools, took the same sort of classes and came to the same understanding.......even if in some bazar language I can't begin to understand.
Regards,
OF
Andreaerdna
If God is the answer, then the question is wrong
Sorry for my poor language skills. This is my 3rd language and not my best for definition..
That being said: what do you mean by "heat radiating out from its source" other than heat tranfert by radiation?
To by-pass my poor language skills take a look to the explanation at atomic level given by english wiki, simplified version:
Start citation
In the atomic theory solids, liquids and gases are made of tiny particles called "atoms". The temperature of the material measures how fast the atoms are moving and the heat measures the total amount of energy due to the vibration of the atoms.
You might imagine conduction to take place when one part of a material is heated. The atoms in this part vibrate faster and are more likely to hit their neighbours. When collisions take place, the energy is passed on to the neighbouring atoms allowing the energy to travel through the solid. (Rather like the way energy passes along a set of tumbling dominos).
The atomic picture also helps explain why conduction is more important in solids: in solids the atoms are close together and unable to move around. In liquids and gases the particles can move past each other, so the collisions are less common.
End of citation
For the little info: nor entropy or enthalpy are needed to be introduced to explain or understand what heat conduction or radiation is, unless you want to complicate it with big words..
Best to you
OF
Well-Known Member
Not to worry, I think you're getting through and I'm certainly not ready to try any other language.......
There are several definitions of 'radiate'. The sort Rene is talking is 'spreading outward (like spokes of a wheel). Spreading out. "Radius" plays into this. "Radiation" as used in Thermodynamics means 'to transfer energy by electromagnetic particles (specifically a photon in our case) rather than direct interaction between 'atomic fields' as described in the stuff you cite. That discussion does not include radiation at all, right?
BTW there are several issues there too (like the domino analogy......) but that's not important now.
Enthalpy and entropy are important because they drive the flow of heat energy. Heat, unlike many things, has no counter. There is no real cold, same as there is no real dark in a practical world. There is only more or less hot (above absolute zero of course). To understand how IR works we need to discuss how it works both ways, but only has net effect if there is a randomness of energy distribution.
I fear I may have wondered too far, hard to stay on tract without seeing the other fellow to see when his eyes glaze over...... What you quote above is part of a start, but we're not anywhere nearer in terms of radiation heating yet I think.
BTW, in a fun way there really are only two routes to heat transfer. Convection is a subset of conduction where the heat is conducted to a fluid (in this case air and other gasses are fluids like liquids but that's a topic for another day) which then moves mechanically in the system and then conducts the heat to somewhere else. That too can wait until later?
Another point that might help is atoms never touch (except in accelerators and some reactors). "Solid matter" is really anything but. It's almost exclusively space between atomic particles. Electrons blow through thousands of atoms of thickness with only a few kV drive. LOTS of holes, not much substance. Conduction heating takes place because of electromagnetic action between nearby electrons (from the outside any atom is a cloud of negative electrons masking what's inside. "Vibrations" (really oscillations) couple from one to the next. Radiation is different. There the E/M energy is converted by Einstein's famous mc2 equation to a "quantum" (a discrete step, in our case a photon) and leaves the mass colder. That photon is like a charged battery, it carries it's 'charge' any distance needed then gives it up to the surface it hits increasing the heat (vibrations) there in it's death. To make it even more fun with words, normally photons radiate out (spread in all directions) so we then have to introduce distance as a factor in formulas to describe radiation transfer (along with emissivity, delta, and surface areas).
In the end it all fits, but it's not an easy game to sit in on mid play.
Over.
OF
Andreaerdna
If God is the answer, then the question is wrong
Not easy to see the line with you, between seriuos and facetious...sometimes
For sure you do like to digress.
Anyway, to close this thread: do we finally agree thermal radiation explain how load is heated (mainly) in so called conduction vapes or do you stand behind the use of conduction as alternative of convection?
Best to you
i guess i'm still confused ... a frying pan is conduction, a toaster is thermal radiation and a hot-air popcorn popper is convection. so a conduction vape (e.g. PAX) is like the frying pan, a conduction vaporizer, like the original soldering iron/globe vaporizers. ime you gotta pack that PAX down tight to get decent vapor (like what i am used to getting).
OF
Well-Known Member
No, we definitely do not agree there. While convection and conduction are much alike, radiation is entirely different and involves the creation and destruction of a sub atomic particle, specifically a photon. It's a "quantum mechanics" thing that can only take place in discrete steps, unlike conduction and convection.
They are quite different from both a physics and engineering POV. And IMO.
Or so they taught me when I went to school all those years ago.
Works for me. But then I'm confused too......but I came in that way.......
I love the 'kitchen breakdown'.......now I think I need a snack.......
Thanks for that.
OF
Andreaerdna
If God is the answer, then the question is wrong
An empty hot frying pan is heating sourround it through thermal radiation, with a lower temperature than toaster wires but closer (to meal) and wider heat source. If you put oil and something to heat (or eat) in your frying pan, significative heat conduction is responsible of cooking your fries or steak, same if you put your toaster in oil (only mentally, not for real) that because differently from air, oil is far better heat conductor. If you put some fluffy thermal insulator in your frying pan and no oil, the main way to describe heat tranfer is through thermal radiation (at least 99,5% of material is separated from the pan or the bowl by air).
If you encapsulate in some futuristic way your load in some heat conductor (no air between heater and heated) than you have the first well named conduction vape, using only some thermal radiation. A frying vape?
As Of knows you can have heat transfert by thermal radiation with 0-nada-zero conduction or convection, but you cannot have heat transfert through conduction between two solids without some thermal radiation too.
Never used a pax but i think as everything, unless you choke air path, more vaporizables gives more vaporized..even if not in the more fast or efficient way
Dining time btw :-)
@OF I do not really know what you refer to when you make dinstinction between physics and engineering POV? do engineer use differents laws than physics ones?
OF
Well-Known Member
NO!!! I don't know that at all, in fact quite the opposite. Please don't put words in my mouth. Conduction heating without radiation happens all the time. NO PHOTONS, NO RADIATION. Period.
Yes, I do know the difference. One is theory the other application in broad terms. They share common ground but it's a big mistake to assume Engineers are experts on physics, or that Physicists can be counted on to build a bridge. For instance they both take steel hardening (Material Science) from two different POVs. One is focused on grain boundaries, participates, dislocations and other fine points of structure, the other in making a better steel part. They tend to the 'heat and beat' end of things.
I've been thinking a bit about the toaster idea HD suggests. The toast comes out warm, say 150F? The element is glowing hot, well over 1500? Heat is radiated to the toast for the most part (no conduction, very little convection). Now lower the heater in your mind. What happens? Takes longer to toast since the temperature difference is less? As we get lower lower radiation fails us more and more it takes longer and longer until it never does toast and all we get is stale bread instead. Or bagel in my case earlier this morning. It toasted precisely because the source was very much hotter so that more photons hit the bagel than left it......it got hotter.
Therefore, to get back to the VM case at hand where the temperature of the pan is no hotter than the load when it's making vapor there can be no radiation left at that point, right?
OF
the physicist reads the recipe ... the engineer cooks the meal.
Andreaerdna
If God is the answer, then the question is wrong
I try to be more divulgative: your bread in toaster has normally zero conduction, near to zero convection (unless wires are on the bottom of toaster?), but if you put a tiny glass between wires and bread you can have easily your bread heated by solely thermal radiation, you can burn easy your bread in your home one, so quite powerful if you think how thin wires are comparing to bread and how far they are comparing to load in VM or MFLB
Other case scenario:
When you heat vapman on heating station heat pass to bowl through thermal radiation too, this because the real contact area accounting for conduction is 100 to 1000 smaller than what you see AT BEST (if they have no imperfection of course) so both thermal radiation an conduction happens there, a good engineer can easily split both contribution to heat transfert but my guess maybe wrong thermal radiation take care of most of heat transfert.
I would like to challenge you to tell us a practical exemple of heat transfert by conduction between two solids (in contact obviously) that not implies thermal radiation.
Kindly
OF
Well-Known Member
Love it! It might be an 'inside joke' but looking out it's priceless. Whoever came up with it understood and deserves some sort of award.
Thanks for the laugh, I needed one long about now.
No, no, no. It heats on the station by conduction. The parts are nearly the same temperature when in contact and heating. Try making vapor with it if you keep the VM just out of contact with the post. If IR was real, it'd still work. But it doesn't???
A practical example of basically pure conduction would be any welded metal connection.
OF
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okay, the egg in the frying pan is cooked mostly (99%) by conduction, not radiant heat, although there certainly would be some radiant heat (black box radiation effect) ... now suspend that egg above the pan surface (i would use sonic levitation, if available) and the cooking would be pure radiant heat - like the toaster.
Andreaerdna
If God is the answer, then the question is wrong
let's sais two metal flat coins welded toghether through lead or else, in a way that both surfaces are without empties spaces..ok?
Then if there is conduction from one side hotter than the other, there must be IR heat transfert by definition. Unless you melted metals making one out of two.. If and when thermal radiation end conduction end at same time and vice versa. There cannot be heat conduction between 2 contigouus bodies without thermal radiation, but you can have heat transfert by thermal radiation only.
OF
Well-Known Member
Only by your definition. The rest of us are using a different one. IR needs photons. I'm saying that a lot, it doesn't seem to get through.......
Heat flow is dynamic, hence the "Dynamics" part of the title. Any such flow is driven by differences in temperature. Just as there's a pressure drop on a garden hose when you open the nozzle or in an electric wire when it's carrying current.
Let's take a conduction example, your computer? The semiconductors generate heat with current flow (Watts is Volts times Amps). That heat is conducted to the body of the part, which gets warm, and the heatsink surface the 'die' (silicon chip) is bonded to for efficient transfer of heat (by conduction). Then to 'heat sink compound' to improve transfer by better contact. It blocks IR BTW, it's quite opaque. It couples it conductively again to the heat sink where conduction continues to the surface of the fins. It then transfers, again by conduction, to the air being moved by the fan and convection takes it out of the system. Not a spec of IR anywhere. Engineers 'run the numbers' on this all the time, every Watt (or calorie) is accounted for.
You can 'see' the photons of real IR. FLIR scopes do this. It focuses like other light in glass lenses. Your phone camera most likely 'sees it' as well. Try looking at it with your handy TV IR remote control, you can see the light in the control flash. We have plenty of instruments to find Infrared Radiation and quantify it very exactingly. If it happened like you believe it would no doubt be well known and researched???
IR is just not a significant transfer mode in VM.
OF
Andreaerdna
If God is the answer, then the question is wrong
Heat transfert through thermal radiation happens between anything at different temperature, that is the definition. Also, if you have heat transfert by conduction there must be a delta t° so IR heat transfert. Deal with it, you don't like it - understand it but it exist despite it and is quite everywhere, you are an IR stove, can you immagine it?
Ps wich is the interest of a welding stuff that improves heat conduction while shielding heat radiation?
OF
Well-Known Member
OK, look, please show me some reference on this new found definition? TIA
Maybe you're not understanding the idea of net transfer of energy? Yes, you radiate IR as does everything above absolute zero (according to emissivity number involved and surface area). You also receive IR energy in accordance to your absorption number (same as emissivity in fact) and exposure. Input minus output tells you if you're heating or cooling. The enthalpy and entropy thing again. How the heat in the system is distributed. You only heat by IR if there is a net coming in. It's dynamic, not static. You can just as easily be cooled by emitting more than you absorb, that's you using IR to heat the world.
Please don't insult me further by saying things like "Deal with it, you don't like it - understand it but it exist despite it". It doesn't sit well when I think I'm right and making sense and you're not. I believe I do in fact understand this good stuff, and will do so unless you have examples you can reference or get some support from our fellow Members. Keep it civil or this discussion can be one sided. At this point casual readers will know I don't agree with you and why. I don't really need to convince you to get what I want.....'keeping it real' on FC.
The advantage of welding in heat transfer is near perfect contact. Conduction heat energy is transferred by interactions of the fields of adjacent atoms (as you quoted above) it has noting to do with IR, there is no photons involved, no radiation. I'm repeating myself yet again.......
OF
nopartofme
Over the falls, in a barrel
@Andreaerdna, this might help. I think you might be using definition #2 here. Definition #1 is the correct one when used in the phrase "thermal radiation".
In the sense of definition #2, to radiate means to spread. Heat is clearly spreading in conduction vaporizers and so it seems logical to use the words radiate/radiation, but those terms carry a different meaning (definition #1) when used to describe the transfer of heat.
Google Knowledge Graph said:
In the sense of definition #2, to radiate means to spread. Heat is clearly spreading in conduction vaporizers and so it seems logical to use the words radiate/radiation, but those terms carry a different meaning (definition #1) when used to describe the transfer of heat.
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