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Don't be fooled by the DNA 20.

Discussion in 'VV/VW APV Discussion' started by Pazazu, Jun 16, 2013.

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  1. dr g

    dr g Moved On ECF Veteran

    Mar 12, 2012
    Paradise
    just the current-temperature chart. all resistance wire works that way. it's part of the reason our rbas work the way they do
     
  2. Mad Scientist

    Mad Scientist Ultra Member Verified Member ECF Veteran

    May 11, 2013
    Smokestack, PA, USA
    I think this is getting circular. The chart takes into account and is calculated based on heat transfer to quiet air. Quiet air is not a great conductor of heat. Quiet air does not have a relevant boiling point and will not act to limit the temperature of a coil heating in it. I take it you are saying that none of that is relevant? If so, then we do disagree.

    The only reason I keep asking about this is just trying to conceptualize and predict what will make a wick coil assembly do what I want it to do without a huge amount of experimentation. I guess the experimentation is unavoidable lol.
     
  3. rayboy55

    rayboy55 Senior Member Verified Member ECF Veteran

    Feb 11, 2012
    Quebec Canada
    I think we went off topic loll !!!!
     
  4. dr g

    dr g Moved On ECF Veteran

    Mar 12, 2012
    Paradise
    As I mentioned in my first post about this, heat transfer between the wick and coil is part of the vapor production equation. But the fact that it takes less current to heat up a smaller wire is basic electronics. That's what we're discussing here.

    The heat transfer and boiling point limitation is not relevant to the general concept of the relationship between wire size, temperature and current. If you are hung up on my use of "temperature" per se, consider "heat energy" instead perhaps. The temperature numbers in air are just a reflection of the increasing amount, illustrative for these purposes. In the end what causes a burnt hit usually is the drying out of the wick and the inability of it to replenish due to the increasing temperature of the coil. Smaller, hotter coils obviously will reach this point in a different way than wider coils.

    As for experimentation, you will of course have to do some but understanding the effect of different variables is key to directing that experimentation.
     
  5. Mad Scientist

    Mad Scientist Ultra Member Verified Member ECF Veteran

    May 11, 2013
    Smokestack, PA, USA
    I hate to keep beating this horse (but I feel compelled lol). What I'm driving at is that any given wire coupled with heat transfer to juice behaves to some degree like a thicker wire in free air, right up to the point where the juice boils off and then it's burnt juice city. It actually behaves "better" than in free air (guess it depends on what's considered better) because it can't get any hotter than the boiling point of the juice, no matter the diameter of the wire -- except to the point where the juice boils off because the heat energy applied to the wick at any given spot is more than it can replenish with juice, or the heat energy applied at any given spot exceeds the wick /coil assembly's ability to transfer heat efficiently from coil to wick.

    Does thinner wire get hotter in quiet air because it has less surface area and therefore can't transfer it's energy to the air as efficiently as a thicker wire with more surface area, or is there something else going on? My "seat of the pants" and a desire to obey the law of conservation of energy tells me that it's not something else. A given wattage should deliver the same total heat energy, no? (Same total energy to the air, or in our case, the wet wick)
     
  6. dr g

    dr g Moved On ECF Veteran

    Mar 12, 2012
    Paradise
    Please see my edit, I clarified the issue a bit. To wit:

    No a given wattage does not emit the same total heat energy. Note that there is no conservation between power in and heat out. Some of the power goes through the circuit. Heat is the "byproduct" of current flow and technically it is "wasted" power in the circuit. Conservation is between heat + the power that makes it through the wire.

    Lower resistance technically means more efficiency, so less heat per watt. This is why low res coils kill batteries faster and why we have to pump up the power to get low res coils to produce.
     
  7. StrappedKaos

    StrappedKaos Moved On ECF Veteran

    May 16, 2013
    Raleigh,NC
    1.1 Jiggawatts.......ARGHHAHAHAHA IT'S ALIVE!
    510 Connection wired to my Memphis Amp down to 0.01 ohms! :evil:
    Ok so back to the thread, I got carried away....
     
  8. Mad Scientist

    Mad Scientist Ultra Member Verified Member ECF Veteran

    May 11, 2013
    Smokestack, PA, USA
    I'm still not sure I'm getting it. Assuming no losses in the rest of the circuit, all of the energy has to make it to the coil, the point of highest resistance in the circuit. Resistance is what results in heat. A true zero resistance circuit would heat only the inards of the battery, the highest resistance in the circuit.

    Losses in the reality based less than ideal circuit of a real mech and coil will result in heat at those connections and thus energy lost. But if the coil resistance drops lower than other losses, it won't be the coil getting the hottest or possibly hot at all. There is conservation of energy in the circuit, but the heat is distributed among each loss; that is the "power that makes it through the circuit." Thus, you are right that there is less heat per watt in a lower resistance coil, but I believe it is because more of the heat energy is lost in other small, yet relatively significant, resistances in the circuit, no?
     
  9. Grogfish

    Grogfish Full Member Verified Member

    From my understanding of electricity it is atoms pushing each other along a path. When that path is reduced they are pushing on each other with more force to get through that path which in turn creates heat. So the smaller path from higher gauge wire creates more heat.
     
  10. Mad Scientist

    Mad Scientist Ultra Member Verified Member ECF Veteran

    May 11, 2013
    Smokestack, PA, USA
    That is basically a useful analogy but it is the electrons, not atoms. You are spot on that resistance will result in heat. One question bouncing around is will identical resistance result in identical heat at a fixed current, factoring out the resistors' abilities to transfer that heat away from themselves. So, will a, say, 1 ohm coil made of 30AWG wire generate more total heat than a 1 ohm coil made of 32AWG wire at a fixed voltage and thus fixed current (and obviously the 30AWG coil will be longer). I say same total heat output. The thinner wire may get to a hotter temperature because it can't transfer it's heat away from itself as efficiently as the thicker, and clearly the shorter, thinner wire coil has much less surface area, but energy is energy and the total heat energy should be the same.

    So it makes maybe more sense, by total heat energy what I'm getting at is that if you placed each of the hypothetical coils in separate, say, 5cc volumes of water, the temperature rise over time in each little tub of water would be identical.
     
  11. StrappedKaos

    StrappedKaos Moved On ECF Veteran

    May 16, 2013
    Raleigh,NC
    I do have a question....

    So I am reading this bulk of knowledge and I think even if off topic this is a wonderful discussion, My question is regarding something I have done in the stereo market or have come to wonder and maybe this will answer those questions and some on the vape side.
    If I wire a coil be it for a sub woofer or for a RBA and it is say 1 ohm as opposed to a 4 ohm setup, am I correct in assuming that because I lowered the ohms it is more efficent? If it is then when I wire a set of 15in subs to 1ohm as opposed to say 4 ohms My amp is working much harder but yet it is more efficently using the power so thats why it does not get as hot as say running at 4 ohms(contrary to what most beleave) it also means my subs are not getting as hot because again using that current more efficently correct? So if what I am saying is persumably correct does that mean that running lower ohms on a RBA is more stable on a thermal aspect? DOes that mean it should last longer and be a better coil than a 3 ohm set up theoretically? Am I headed in right direction and can someone that has more knowledge on this subject help to understand this enigma? dont mind my horrible spelling please, THanks in advance. Strapped
     
  12. dr g

    dr g Moved On ECF Veteran

    Mar 12, 2012
    Paradise
    Same total heat output, yes, however the volume and surface area of the 32AWG coil will be far smaller than the 30AWG, so the heat emitted per size unit of that coil will be higher. That is not the result of heat transfer, that is inherent to electrical physics. Heat transfer considerations come after that.

    In general yes, you are on the right track. A wide-gauge low-ohm coil will generally be more durable than a thin-gauge high-ohm coil. However there are other aspects to that equation, such as the actual wire temperature reached, the effect of the load on the current flow (regulated vs unregulated), wick efficiency, etc.
     
  13. Mad Scientist

    Mad Scientist Ultra Member Verified Member ECF Veteran

    May 11, 2013
    Smokestack, PA, USA
    If you ignore heat transfer as to "come after that," the basic electrical physics of increasing the temperature of a wire, any wire, is (I^2)R or more specifically, Q=(I^2)R, i.e., Joule's First Law. Not to be flip, but what basic electrical physics are you on about? Once we move on to heat per unit of area, we have to consider heat transfer. Ignoring heat transfer would have any current carrying wire tend toward infinite temperature over time. We know that's not what happens.
     
  14. dr g

    dr g Moved On ECF Veteran

    Mar 12, 2012
    Paradise
    "Once we move on to heat per unit of area, we have to consider heat transfer." Yes, after the basic fact of more heat per unit of area.

    I don't know what's hanging you up. Same amount of heat, much smaller surface. To think that would not be consequential fails even common sense.

    I don't know if it will help you but in a properly functioning atomizer the coil is not completely and continuously immersed, if you do that you will not get atomization.
     
  15. Mad Scientist

    Mad Scientist Ultra Member Verified Member ECF Veteran

    May 11, 2013
    Smokestack, PA, USA
    It's because when the smaller area is well coupled with the heat absorption of a wet wick, it no longer behaves like just a smaller area. So it doesn't seem real helpful to push heat transfer aside for later Yup, the temperature of a point can be measured hotter in quiet air. If you close coupled it with a theoretical infinite heat sink, it's temperature wouldn't change at all. A wet wick is in between there somewhere ... Not real useful lol.

    Add to that the fact that a well coupled wet wick will behave much like an infinite heat sink at the liquid boiling point (until the liquid evaporates and isnt relaced) and you have a system that depends entirely on heat transfer and can ignore your smaller surface area, except and only to the extent that surface area is relevant to the coupling. So we go another circle -- it's the total heat and the thermal coupling with the wet wick we likely really want to initially look at. Then on to other issues, lol.
     
  16. dr g

    dr g Moved On ECF Veteran

    Mar 12, 2012
    Paradise
    The wire itself is emitting a higher heat intensity (heat per area unit) from its surface if it is smaller. Before ANY heat transfer considerations. Heat transfer may actually mask that, that could be where you are getting hung up.

    Submerging the coils in the same volume of liquid effectively normalizes the volume/surface area. But that's not what happens in our atomizers unless maybe they are flooded, which is not how they work.
     
  17. Mad Scientist

    Mad Scientist Ultra Member Verified Member ECF Veteran

    May 11, 2013
    Smokestack, PA, USA
    I'm not getting hung up and what you call "masking" is the area of the physics of it that I'm interested in. What happens in our atomizers is precisely what happens when a coil is immersed in a liquid (albeit a small volume of it) with the differences being much of what is not optimal. Flooding is simply more liquid than we want for the total heat we have, not some different animal. I'm still mulling and modeling but initially it appears that a wet wick and coil behaves like a coil immersed in a high viscosity liquid (or maybe it's more like immersion in a liquid with a low boiling point -- still mulling and modeling lol).

    Where you are hung up is thinking that the coil is emitting some measureable heat "intensity" before heat transfer is considered and thus magically emits more in some imaginary initial state before any of its energy is instantaneously absorbed by the wet wick. What's really happening is the juice in the wet wick is absorbing the heat generated and the factors that influence how it absorbs are the relevant ones. Yes, I admit energy per unit of surface is one of those factors, but only one, because, again, with good coupling, the coil / wick assembly will tend toward behaving monolithicly.

    This discussion has been useful, thanks for that, as I now see what's important to focus on.

    IMHO, you can throw the quiet air chart in the trash because while it might be appealing to use to try to explain what is happening and why by oversimplifying what's really going on, it does not even scratch the surface of what is in actuality really going on and thus what is involved in designing better wick / coil assemblies.

    Thanks again. :)
     
  18. dr g

    dr g Moved On ECF Veteran

    Mar 12, 2012
    Paradise
    Well, in practice, it behaves as I have described because in a functioning atomizer you don't get good enough coupling to equalize coils of differing wire diameters. The wire diameter makes a big difference in exactly the way I described. You are deliberately trying to downplay the effect for some reason or another. But the effect is real and very significant. The still air chart helps illustrate the effect by exaggerating it, the concept remains the same with a liquid before phase change ("responsiveness"). If you measured localized temperature of the wire you would find it higher in the thinner wire at all points in the curve up till phase change, as heat transfer does not happen instantaneously and homogenously. If you were running a power high enough to starve the wicks, the thinner coil would reach that point sooner than the thicker coil, assuming similar wicking.

    You are asserting that, given the same resistance, two coils of different wire diameters should run identically. All I can say to that is, try it yourself. You'll find out really quick you're wrong.

    Ironically, I believe it's the phase change, the thing that makes you think you're right, that makes you wrong.
     
  19. dr g

    dr g Moved On ECF Veteran

    Mar 12, 2012
    Paradise
  20. tomzgreat

    tomzgreat Ultra Member Verified Member ECF Veteran

    Jun 5, 2009
    Chino California
    HI All,

    Below is a post that demonstrates, Low Gauge and High Gauge at the same Ohm level.

    The results are exaggerated but do illustrate quickness in heating up of Low Gauge vs High Gauge.
     
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