Interesting reads!
Sorry I've been away... the move of my home and shop has been real hectic!
A few thoughts since I've been away... sorry, this will be a long one!
First, Titanium is not inert,
@SamuraiSam. Titanium immediately oxidizes in air. This oxide layer is what gives titanium its corrosion/oxidation resistance. Same for aluminum, stainless steel...etc...
This is why titanium is not considered a noble metal like gold.
But essentially it does act like one once that oxide layer is formed. So... close enough!
Nichrome also acts the same way, producing an oxide layer that protects the metal from oxidation, even at extremely high temperatures. This is why it's such a popular heating element material.
This oxide is Chromium (III) Oxide. Widely considered as safe, with a long history of use. Super hard (8-8.5 on the Mohs scale), extremely scratch resistant.
There is another metal that gets its corrosion/oxidation resistance from a thin layer of Chromium (III) Oxide, and that's stainless steel.
Both SS and Nichrome form a protective layer of the exact same oxide.
I always look towards industry when sourcing materials. You don't see stainless being used in industrial applications as a heating wire. Why? Because we have base alloys specifically designed to perform much better in high temperature environments. Stainless just won't last.
In a wide cross section, I think stainless steel will hold up fine for our relatively low temperature purposes, and indeed people do sing its praises for taste. But It's a mystery to me where those taste differences come from. Perhaps it only exists when the metal is un-oxidized, submerged in liquid. Perhaps the liquid composition is chemically reacting to the un-oxidized surface. Or perhaps it has more to do with metal suppliers... variances in composition from one source to another...
This vape world is still young.. and the nuances of what impacts the experience are still to be explored.
In any case, I am exploring a heater designed with very thin ribbon/sheet. The same thickness as a AWG 39 wire. Nichrome behaves very nicely at this thickness, very strong stuff, will survive the heat just fine. But I am worried about stainless. I fear that hot spots will develop over a short period of use.
In choosing my heater material, I went with an industry standard, one that has shown to perform exceptionally under extremely high temperatures with a long life span. I also believe my application is a tad different.. because the metal is allowed to form a chromium oxide layer, there should be no base metal to interact with the air stream.
BUT.... taste..user experience...all this will come into play. And the beauty here is that if you don't like Nichrome (or have an allergy), you can swap in a stainless coil (If I can get stainless to work...that is).
Anyhow.. back to task.
I am on a heater module that I'm very happy with now. Perfectly even heat from wall to wall, no stir, very quick heat up/heat down. Under load It draws about 6 - 6.5 amps. I would rate this at a medium power HM.
I have added a design element. A metal screen between the heater and the chamber. This is both a heat diffuser screen, and keeps material from falling down onto the heating element. Works nicely.
Special Topic Talk!
This is going to get a bit fuzzy/hypothetical....
I am starting to get a feel for what this vape IS. And it's been clear that the ability to swap heater modules is essentially acting as a form of mechanical regulation.
Sure I
could offer a single, high powered HM, to cover all bases... just click the fire button ON/OFF, and control draw speed to regulate temperature... but..
Can we reach the performance levels of a regulated device, with a mechanical circuit? Lets discuss.
What IS heat regulation.. anyhow.. What are the goals. Well..easy.. it's to aid in soaking a chamber of herbs with a stream of heated air at a set temperature, regardless of the other variables involved.
All things being equal (airway geometry, heater surface area, bowl size, etc..), what are the
ever-changing variables that only control heat output from the heater?
Power into Heater, ambient air temp, air speed. That's about it.
Electronic regulation obviously does a great job of smoothing out those last two variables... it doesn't care what the ambient temperature is.. or the air speed. By constantly changing the power into the heater, the desired end goal is achieved.
But what if there was another way.
In my experience, ambient air temp is a relatively small variable. It's more of a seasonal change, less of an ongoing changing variable. So lets disregard it for now.
Regulation gives you the luxury of keeping the fire button ON, taking a draw, and getting perfect heat. This is what I am after. IMO, fire button ON/OFF time is a tricky way to control heat. It's not user friendly, and it certainly sucks in group settings where no one has any experience.
The fire button ON/OFF regulation techniques should be reserved for experienced users, imo. Not knocking them, not at all, it does give the user a sense of great power... and riding that line can be very enjoyable!
But again.. I am after what I call the equilibrium.
When energy into heater roughly matches the energy going out of said heater (in the form of heat), that is the equilibrium.
If you had a fan at a set speed, moving air through a heater receiving a constant power, heat output should remain perfectly constant.
We need that equilibrium to occur at the users comfortable draw speed, at the users desired temperature.
This is where swappable HM's come into play.
Lets say you enjoy a medium draw speed. You also enjoy a medium/high vaporization temperature.
So you want a HM that will reach that medium/high vaporization temperature, at a medium draw speed. If you keep the draw speed constant, you can keep the fire button ON for as long as you like, the temperature will remain fairly constant.
For those who like hard inhales, or use water tools, you may want to swap in a higher powered heater designed to reach equilibrium at a fast air speed.
With the current medium powered heater, it feels custom fit to me. I just keep the fire button ON, and draw at a perfectly comfortable rate that is easy for me to keep constant. If I decrease my inhale rate I can feel the temperature climbing (and becoming harder to control), if I increase inhale rate, I can feel temperature decreasing.
So.. all this to say that my focus has shifted somewhat... I think that the heater module itself is essentially an infinitely adjustable variable resistor.
Obviously achieving the same level of performance is unrealistic.. since electronic regulation (newer TC) has the advantage of being able to overcome changing variables, like voltage drop, ambient temp, draw speed...
But.. I think we can come close.. and it'll be different.. a new way of looking at regulation.
Okay I'll stop rambling now, haha.
p.s. - Voltage drop, ah yes, can't forget about voltage drop. Yes, it's a variable that needs to be compensated for in other areas, mainly draw speed. You can also swap in a new HM once your battery is under a certain voltage, to gain back the power you lost.
Whoops I meant the mistvape touch, my bad! It's not the first time I've mixed those two up.
