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Sub-Ohm... what's the point?

Published by State O' Flux in the blog State's Stuff. Views: 1454

A few days ago, this post popped up... with my answer to follow.

Although you provide no detail regarding your net resistance and wire gauge used... everything you need to be successful at higher wattages can be found in Ohm's law formulas, the Steam Engine coil modeling program... and an understanding of "heat flux". Heat flux is a number representative of coil radiant heat, expressed in milliwatts per millimeter squared.

I'll offer one example, which will apply to all comparisons, regardless of the variables, save for the constant of heat flux.

If you have a 32 gauge single coil at 1.8Ω, 8 watts is plenty for producing a "nicely warm" heat flux of 317 mW/mm².
To reduce that temperature, all one needs to do is lower the wattage, and/or increase the resistance value.

Why the hell is sub-ohm so damn popular?

To put it bluntly, sub-ohm or "high-performance vaping" is so damn popular because of increased coil surface area and higher heat values.

The net coil surface area of the above build/wattage is 23.95 mm². Flavor and vapor concentration, for a given heat flux, are commensurate with surface area.

With sub-ohm, it's not so much the amount of heat you can produce (although in some instances, it's advantageous), but rather the increase in net coil surface area, along with the amount of wick exposed to that surface area.

If our net surface area is twice that (or more) of the previous 32 gauge build... it would stand to reason that for the same heat flux, you'll produce twice the flavor concentration and vapor volume and/or density.

Is it a true 2:1 or more ratio? Not exactly. There are assorted losses, but depending on the juice PG/VG ratios used, along with a few other physical and electrical variables... empirical observations indicate that it's not too far off.

To obtain an 317 mW/mm²+/- heat flux from say, 40 watts, one of many optional possibilities would be... a 27 gauge, dual parallel coil build of 0.4Ω net resistance - producing a 313 mW/mm² heat flux.

In this example, the juice vaporization potential more than doubles from our previous 1.8Ω build - with a net surface area of 61.55 mm² - an additional 37.6 mm² of net coil surface area.

Use Steam Engine to run any set of comparable high & low resistance numbers you wish. To obtain a valid surface area comparison, adjust wire gauge, parallel coil count, net resistance and wattage, with the goal of obtaining relatively constant HF values... try to stay in a 10 mW/mm² plus/minus window.

That's All Folks! :D

(If you have any questions, please PM me. If the question and response merit sharing with others, they will be added to this article. Thanks)
FilthyPazuzu and Ryedan like this.
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