What parameters influence the coil temp?

[zoiDman]

It just Dawned on me what the Problem with a Material is if its Resistance doesn't Change much over the Working Voltage Range with respect to Heat.

Since Resistance Doesn't Change Much when the Coil Wire is at Room Temp or Angry Red, the Board doesn't have anything much to Measure. All the Resistances are Relatively the Same. From a Weak Hit up to Breathing Burnt Marshmallow Smoke.

Got It.

 

[beckdg]

It just Dawned on me what the Problem with a Material is if its Resistance doesn't Change much over the Working Voltage Range with respect to Heat.

Since Resistance Doesn't Change Much when the Coil Wire is at Room Temp or Angry Red, the Board doesn't have anything much to Measure. All the Resistances are Relatively the Same. From a Weak Hit up to Breathing Burnt Marshmallow Smoke.

Got It.

And slight batch inconsistencies could potentially wreak havoc when beginning with such a low coefficient in an alloy. Your China wire might get to 900 deg while your EU wire is spot on. Or vise versa.

 

[rusirius]

Couple of points I want to touch on and reaffirm here...

First, as mentioned, the reason they use nickel is because of it's temperature coefficient of resistivity. That's just a really fancy way of saying "what percentage the resistance increases as temperature rises". In other words, with nickel, the resistance of the wire itself changes a LOT more drastically as it's temperature rises than does kanthal. Because of this, it means it's easier to measure with more accuracy... Let's say you're trying to measure the temperature of a piece of rope by measuring it's change in length. You know it's length at 70 degrees and want to "stop heating the room" when it reaches 200 degrees.... One type of rope changes 1mm in length for every 100 degrees change in temperature... The other type of rope changes 10mm for every 20 degrees.... Which type of rope would you use? It's going to be far less accurate and far harder to measure when the change is very small... But with the other rope, because it changes so much more as the temperature climbs it's much much easier to get pretty close to that 200 degree mark...

Now as for the "temperature of the coils" this seems to be a very common misconception. One that I've addressed in another post a few times.

Here's the thing you have to understand...

Go try to burn a pot of water.... Burn the water in it.... Now while some of you might be saying, "I'm sure my wife could" The truth is... You can't... It doesn't matter if you put it on a little portable stove top or on a smelting furnace... The water will ONLY ever reach 212 degrees (at sea level). The only thing putting more "power" does, is cause it to boil more rapidly. Why? Because once the water reaches it's boiling point, it turns to vapor.... That vapor carries the excess heat away... The more "energy" you put into the water, the faster it turns into vapor...

The same thing applies to our e-cigs... The mixture of our PG and VG form an azeotrope with a given boiling point. Whatever that boiling point is, assuming there is enough power being put into the coil to generate the heat necessary to vaporize the liquid, is what the temperature of the coil will be. Because any energy in excess of this will simply vaporize juice faster. Just as adding more heat to a pot of boiling water will simply make it boil faster. The temperature of the coil will remain the same.
This is why the more power (wattage) we run, the more vapor we get.

That is all assuming the wicking can keep the coil saturated. If the coil is not fed juice fast enough to keep up, then it will dry out and at that point temperature will skyrocket.

 

[Alien Traveler]

Go try to burn a pot of water.... Burn the water in it.... Now while some of you might be saying, "I'm sure my wife could" The truth is... You can't... It doesn't matter if you put it on a little portable stove top or on a smelting furnace... The water will ONLY ever reach 212 degrees (at sea level). The only thing putting more "power" does, is cause it to boil more rapidly. Why? Because once the water reaches it's boiling point, it turns to vapor.... That vapor carries the excess heat away... The more "energy" you put into the water, the faster it turns into vapor...

The same thing applies to our e-cigs... The mixture of our PG and VG form an azeotrope with a given boiling point. Whatever that boiling point is, assuming there is enough power being put into the coil to generate the heat necessary to vaporize the liquid, is what the temperature of the coil will be. Because any energy in excess of this will simply vaporize juice faster. Just as adding more heat to a pot of boiling water will simply make it boil faster. The temperature of the coil will remain the same.
This is why the more power (wattage) we run, the more vapor we get.

Not exactly. System “wire-wick-liquid” is not in state of balance, so non-equilibrium thermodynamics should be applied (which I barely remember). Coil (wire) could be hotter than boiling point. If it is overheated it will be surrounded by vapor, which will limit direct contact with liquid.

As for azeotropes … Every azeotropic mixure has its very specific concentrations. For example for system alcohol-water azeotropic solution is 96% alcohol and 4% water (every moonshiner should know it). Only at that concentrations vapor will have the same proportions of alcohol/water as liquid have.

Juice in no way is azeotropic solution. I think juice vapor has about the same composition as juice itself only because the coil is well overheated and vaporize all ingredients fast enough independently of their boiling point. But it is only my theory, I am not an expert at all in non-equilibrium thermodynamics.