The costs of running this huge site are paid for by ads. Please consider registering and becoming a Supporting Member for an ad-free experience. Thanks, ECF team.

Low resistance is a byproduct, not the goal, or... more things to hurt your head.

Published by State O' Flux in the blog State's Stuff. Views: 1016

Low resistance is a byproduct of a (mostly) unrecognized benefit... not the goal.

"It's that damn SoF again... talkin' 'bout that damn heat flux. Get him! - burn him at the stake!".

Don't light the match just yet...

More surface area means more juice is vaporized for a given duration of adequate, applied current.
In the simplest of terms... more surface area equals thicker clouds, more flavor.

Our 'functional goal' is made of two parts. Coil surface area, and a wattage sufficient (or more) to support that surface area with enough radiant heat (heat flux) to vaporize e-liquid.
That low resistance 'number' is the result of increased surface area... and a simpler way to provide a recognizable value than using an actual surface area value. Resistance is the value we all learn up front when we get into vaping. It's engrained... just like wire gauge is an easier way to say 'more' than surface area.

But that's not a completely true statement.

"Damn it SoF... here we go again with these 'maybe' answers".

Surface area doesn't know anything about wire gauge... you can have a thinner wire, and have more surface area than a thicker one. It just takes more length of wire - along with the higher resistance value hitching a ride - to obtain that surface area.

"Hold on now... what the hell did he just say? This is starting to make... not a lot of sense".

That's right... you can have the same surface area (83 mm²) with 30 gauge wire at 1.5Ω as you can with 26 gauge wire at 0.38Ω... again, 83 mm². And these comparisons can occur over and over with other gauges/resistances ... until we actually exceed an atomizers physical space to contain wire.

Lets apply a bit of wattage and see what we get. it takes 34 watts to obtain a HF of 200 mW/mm² +/-... for both builds.

Yep... the same power produces the same temperature for the same wattage... and yet, the wire gauge is different. As I said up front... it's surface area first. Maybe.

"'Maybe... MAYBE'? I vote we burn him now, before he says anything else. OK, I'll bite... Is one better than the other?"

Glad you asked. Yes... the 30 gauge build is a little more efficient than the 26 gauge build, because even though the surface area is the same, the thicker wire has greater mass and density, making it a bit slower to reach functional temperature.
"Time to temperature is 17.5 mJ/K for the 30 gauge vs. 28.4 mJ/K for the 26 gauge... where the lower value is "faster" than the higher one.

"So, why is everyone going to thick wire, if it's less efficient than thin wire?"

This is where surface area and resistance start to share desired characteristics. We could use that 30 gauge wire to make a 0.38 coil, but at a dramatic loss of surface area... and we all know that surface area is a high priority.
To get our surface area back, at the resistance we desire, we need thicker wire.

"But wait... screw desired resistance. Why don't we just run "normal" resistances with thin wire to get the same surface area?"

Again... we run into issues with physical space. For example, lets try and double the above 83 mm² surface area to a nice fat 166mm² +/-. We'll do it with the same wire gauges.

OK... to get 166 mm² of surface area, we need lengths of 133mm for 26 gauge wire and 211mm of 30 gauge wire.
Using a 2.4mm mandrel, the 26 gauge will make a single 13 wrap coil, while the 30 gauge will produce a 23 wrap coil.
For all practical purposes, we need either a bigger atty, a much larger mandrel (and some magic wicking to go with it), splitting the single coil into parallel duals (or more)... and/or thicker wire.

Of those most practical and likely to occur... whata' ya' think? I'm leaning towards the multiple parallel coils and thicker wire... with the byproduct of lower resistance. Did I mention that we need higher wattage power supplies to support all this? No... oh well.

And what direction has vaping taken in the past few years? Oh yeah... right. :rolleyes:

Still want to burn me at the stake?

"Maybe... tomorrow good for you?"
ST Dog likes this.
You need to be logged in to comment
  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.
    Dismiss Notice