Titanium wire, vaping and safety

[retird]

If you look at the reference TCR curve under "Custom" in EScribe I think you will see that the curve compares to the Ni200 TCR as shown in Steam Engine...thus just a reference..... probably good to know so somebody won't mistake it for a Ti TCR....thx for letting me just inject this into you guy's very interesting thread....

 

[druckle]

Because I'm interested in Titanium I entered the Steam Engine data in Escribe for Profile 2 from day one. Later as a part of playing with the software I did a "restore defaults" command. When I looked at the values for RST in profile 2 I did not realize that the data weren't exactly like that for my previous Steam Engine curve. The only point is not to make the mistake of assuming anything as I did.

Duane

 

[tchavei]

Correct. Ti is not mentioned. Profile 2 has data but no name. At first glance the data look like the Steam Engine data. It's only the 800F point that is different so it's easy to assume that the data reflect that required for Titanium.

Duane

Maybe that curve is a remanescent of vaping dry stuff that makes you laugh experiences? [emoji14]

Regards
Tony

Sent from my keyboard through my phone or something like that.

 

[druckle]

Maybe that curve is a remanescent of vaping dry stuff that makes you laugh experiences? [emoji14]

Regards
Tony

Sent from my keyboard through my phone or something like that.

I did seem to have a craving for Oreo cookies after vaping.

Duane

 

[awsum140]

I hate built-in "gotchas" like that.

 

[AtmizrOpin]

26 gauge Ti, 8 wraps. TCR VALUE (nickel purity adjustment) set to 50. Great vape.

 

[roxynoodle]

Hmm, I just built another ti atty for my new sx mini m today and that one is working great, too.

I've been running between 405°-430°F.

 

[WideO]

FWIW, with the Mini M and the new firmware, I am setting the Ti1 temps about 30°F higher than the exact same atty/build/juice/power level with NI200 to get the exact same performance/taste. Not very scientific I know, but I don't think I'm wrong. (for numbers: 450°F instead of my usual 420°F at 23J). I obviously don't mind as it's a really great vape, but I guess there's still some work left to be done with the different wires and TCR's, as 420°F with Ti1 in this case is slightly aneamic (bounces against the temp limit too much) and 450°F "just right".

 

[Yozhik]

FWIW, with the Mini M and the new firmware, I am setting the Ti1 temps about 30°F higher than the exact same atty/build/juice/power level with NI200 to get the exact same performance/taste. Not very scientific I know, but I don't think I'm wrong. (for numbers: 450°F instead of my usual 420°F at 23J). I obviously don't mind as it's a really great vape, but I guess there's still some work left to be done with the different wires and TCR's, as 420°F with Ti1 in this case is slightly aneamic (bounces against the temp limit too much) and 450°F "just right".

I'm not an expert in this area, but it may be that due to the difference in materials that Ti needs to be at a higher temperature to achieve the same result. The specific heat of Ti is .54 kJ/kg K, while the specific heat of Ni is .44 kJ/kg K. So the first thing I'd expect based on that is that I will need more energy to heat Ti to the right temperature than Ni. The second thing I'd assume is relevant is thermal conductivity, which for Ti is 19 W/m°C and for Ni is 62 W/m°C. As one can see, Ni is 3 times better at conducting heat than Ti, which may mean that Ni is more efficient at putting heat into the e-liquid for vaporization. So this, and perhaps other differences in material properties (e.g., skin depth due to PFM), might be why Ti needs to be used at different temperatures and Joules settings than Nickel.

Again, I'm not an expert on this, so I could be wrong, but if the different settings are required, this is my educated guess as to why.

 

[vapealone]

I'm not an expert in this area, but it may be that due to the difference in materials that Ti needs to be at a higher temperature to achieve the same result. The specific heat of Ti is .54 kJ/kg K, while the specific heat of Ni is .44 kJ/kg K. So the first thing I'd expect based on that is that I will need more energy to heat Ti to the right temperature than Ni. The second thing I'd assume is relevant is thermal conductivity, which for Ti is 19 W/m°C and for Ni is 62 W/m°C. As one can see, Ni is 3 times better at conducting heat than Ti, which may mean that Ni is more efficient at putting heat into the e-liquid for vaporization. So this, and perhaps other differences in material properties (e.g., skin depth due to PFM), might be why Ti needs to be used at different temperatures and Joules settings than Nickel.

Again, I'm not an expert on this, so I could be wrong, but if the different settings are required, this is my educated guess as to why.

Interesting.
But we may need to consider density as well to make the equation even more interesting (Density of Ni200 is two times higher than Ti1 isn't it? If yes, specific heat of a TI wire is actually lower than same gauge/length Ni, right?)

Besides I have carried out a stupidly inappropriate experience myself: running the very same Kanthal/Ni hybrid coil both on Ni and Ti settings on the beta.
In theory, TCR/TFR should be very Ti-ish of the coil I have used and indeed it worked (and still working) as supposed on Ni mode but on TI the universe broke I had to set temp settings extremely high to get anything out of it. And again: very same material very same setup and way off temp offsets.
So for now, I stick with Ni mode .

Ps: we are always referring to Ti TFR curve however I guess that quite a few of this curves are actually simply lines like Steam-engine's one. Ok, technically it is still a curve with zero curvature. Either way, using constant TCR as an approximation means a simple equation should give an acceptably accurate temp value

 

[Yozhik]

Interesting.
But we may need to consider density as well to make the equation even more interesting (Density of Ni200 is two times higher than Ti1 isn't it? If yes, specific heat of a TI wire is actually lower than same gauge/length Ni, right?)

Besides I have carried out a stupidly inappropriate experience myself: running the very same Kanthal/Ni hybrid coil both on Ni and Ti settings on the beta.
In theory, TCR/TFR should be very Ti-ish of the coil I have used and indeed it worked (and still working) as supposed on Ni mode but on TI the universe broke I had to set temp settings extremely high to get anything out of it. And again: very same material very same setup and way off temp offsets.
So for now, I stick with Ni mode .

Ps: we are always referring to Ti TFR curve however I guess that quite a few of this curves are actually simply lines like Steam-engine's one. Ok, technically it is still a curve with zero curvature. Either way, using constant TCR as an approximation means a simple equation should give an acceptably accurate temp value

Yep, didn't consider density. Though between specific heat and thermal conductivity, I'd assume the later to be more relevant. Maybe in a 26 gauge coil the difference in heat transfer from the core of the coil to its surface causes a difference. However, maybe the coil is so thin that it doesn't matter as much. I also believe the skin depth of Titanium is much higher than Nickel, so if that's a factor in where heat is generated (e.g., the skin or more to the core), that could be relevant to heat transfer.

The main thing is that the method currently used relies on measuring resistance of a wire to assume it has reached a certain temperature. If issues like skin depth and heat transfer are relevant, for which I lack the expertise to determine, that could mean the assumption that temperature is same across the plane orthogonal to the wire is false, even though the wire is at the desired resistance.

 

[druckle]

Yep, didn't consider density. Though between specific heat and thermal conductivity, I'd assume the later to be more relevant. Maybe in a 26 gauge coil the difference in heat transfer from the core of the coil to its surface causes a difference. However, maybe the coil is so thin that it doesn't matter as much. I also believe the skin depth of Titanium is much higher than Nickel, so if that's a factor in where heat is generated (e.g., the skin or more to the core), that could be relevant to heat transfer.

The main thing is that the method currently used relies on measuring resistance of a wire to assume it has reached a certain temperature. If issues like skin depth and heat transfer are relevant, for which I lack the expertise to determine, that could mean the assumption that temperature is same across the plane orthogonal to the wire is false, even though the wire is at the desired resistance.

Aren't skin effects primarily an issue with high frequency? Since we are dealing with DC is the skin effect an issue?

 

[Yozhik]

Aren't skin effects primarily an issue with high frequency? Since we are dealing with DC is the skin effect an issue?

Any modulated signal has both DC and AC components. With something like PFM, there's going to be stronger AC components than if you do just amplitude modulation. If it is a factor, than the benefit is faster heating to the skin of the conductor (which is why AC is often the preferred method for temperature control in other applications), but I don't know if it is a factor or not. Thus, I'm just pointing out that it could be a factor, until someone determines otherwise.

 

[vapealone]

Yep, didn't consider density. Though between specific heat and thermal conductivity, I'd assume the later to be more relevant. Maybe in a 26 gauge coil the difference in heat transfer from the core of the coil to its surface causes a difference. However, maybe the coil is so thin that it doesn't matter as much. I also believe the skin depth of Titanium is much higher than Nickel, so if that's a factor in where heat is generated (e.g., the skin or more to the core), that could be relevant to heat transfer.

The main thing is that the method currently used relies on measuring resistance of a wire to assume it has reached a certain temperature. If issues like skin depth and heat transfer are relevant, for which I lack the expertise to determine, that could mean the assumption that temperature is same across the plane orthogonal to the wire is false, even though the wire is at the desired resistance.

Now you are loosing me. Again
But at least I know that temperature is not even the same across the whole length. Likely temp variance on the cross section just makes it more funny. And we didn't even considered the fact that our coils are cooled differently (I.e. mainly by liquid on one side and mainly by evaporation on the other and who knows in-between).

And it leads me thinking that Yihi either trying to overthink Ti or simply picked a wrong TCR/TFR curve. As in my case (i.e. same coil, same TFR at given temp) calculated (and relative) temp shouldn't be that off unless they are trying to compensate for Ti as material somehow and/or using wrong data.
Especially considering that Ti is reported working as supposed on virtually any Ni mods.

Anyway, it doesn't bother me much. I don't know the relevant attributes/properties of my liquids either, nor the simple temp changes along the length of my coil. It is just interesting

 

[tchavei]

I just had a brain stroke. Thank you guys. [emoji14]

Regards
Tony

Sent from my keyboard through my phone or something like that.

 

[Yozhik]

I just had a brain stroke. Thank you guys. [emoji14]

Dang it, I was hoping you would have the answers.

 

[awsum140]

I'll throw in a few cents regarding skin effect. Skin effect, to my recollection from electronics and ham radio, doesn't become much of a factor until the frequency gets over 100MHz. I have no idea what the sampling rates are for PWM chips, but I seriously doubt that it's much over 10 or 20 KHz. Even if there's a ton of harmonics, they would be at such a low power level if they got into the 100MHz and up range, it wouldn't noticeably effect power/heat.

 

[tchavei]

Naa. If Duane hasn't then certainly not me.

Only thing I can add is that our coils are so small and thin, the temperature difference between the core and outer skin is probably negligible or even non existent after a few nano seconds.

We are powering these tiny coils at up to 200w. With that amount of electrons flowing, I don't think any possible Ti inefficiency will become apparent.

Regards
Tony

Sent from my keyboard through my phone or something like that.

 

[Yozhik]

So I did some more research. Skin depth is a function of relative permeability, which for conductors like gold, copper, silver, etc. is around a value of 1. Pure Nickel though has a much higher relative permeability of 600. The diameter of 28 gauge is 321 μm. At 100 Hz, the skin depth is 537.4 μm (so it's not an issue). At 1 kHz, it's 169.9 μm (we're close to the crossover point). At 10 kHz, the skin depth is 53.7 μm. At 20 kHz, the skin depth is 38 μm.

So somewhere slightly above 1 kHz, skin depth becomes a factor in nickel coils. How important of a factor, don't know.

Titanium is like gold or copper, so it has a relative permeability around 1. This means skin depth will be of concern only beyond any frequency we care about. That being said, if the skin depth was a substantial factor for tuning the temperature control algorithm for nickel, that same algorithm may not be optimal for titanium.

 

[Yozhik]

As anecdotal evidence regarding skin depth, someone was complaining about the SXM causing his Kayfun's to heat up. He wasn't using the gold spring upgrade, so I suggested he take it out and that resolved the problem (he reversed the AFC or whatever so it was a direct connection). Stainless steel, which I assume was the original type of spring used by the Kayfun, has a relative permeability higher than that of pure nickel (due to the iron in it), so it's more sensitive to the effects of skin depth and consequently faster heating.