Coil size

[Fuzzy Bruce]

Question for the experienced rebuilder

If two coils are the same resistance, say 1.4 ohms, one using 30 g and the other using 28g, will there be a difference in the quality of the vape in a KFA style atty at between 10-15 watts? Both being about the same ID.

 

[Fishee]

I think it's gonna be a different vape because you're gonna be dealing with a different surface area.
Even though the ID is the same and the ohms the same.
More surface area, more liquid on coil, more vapor from coil.

 

[State O' Flux]

Using Steam Engine... at 15 watts, with 5mm tails and 1.4Ω as constants:

28 gauge, at 78.2mm long will be good, with a heat flux of 190 mW / mm².
30 gauge, at 49.2mm long will have a quite a bit warmer heat flux of 381 mW / mm².

At 20 watts, 28 gauge will be on the somewhat warm side at 254 mW / mm², while 27 gauge (98.6mm long) at 179 mW / mm² would be back in the commonly preferred range.

Heat flux is an indication of peak coil temp. I tend to build in the 180 to 280 range, although I have dipped down to as low as 140... as I don't mind a bit of heat dwell time or 'lag'.

With surface area... it can be axial - long coils with lots of wraps... and it can also be circumferential - shorter coils, where the surface area is derived from a larger diameter. I seldom go below 1.5mm... although for some applications, particularly for use with ceramic rod wicks in an RDA... I've gone as large as 3.5mm ID. The resulting coils are of course shorter... given a common desired resistance value.

 

[Fuzzy Bruce]

Thanks. So, when building efficient coils, the heat flux should be as important as the desired ohms and on Steam engine, this info can be found using the advanced tab.

I now feel like I am taking tiny little baby steps instead of crawling around blind.

 

[State O' Flux]

Thanks. So, when building efficient coils, the heat flux should be as important as the desired ohms and on Steam engine, this info can be found using the advanced tab.

I choose desired resistance first, Bruce... because it's what ever you want it to be - then the wire gauge that provides the best composition of surface area/heat flux/heat dwell time (capacity)... for that resistance.
I'm a bit of a surface area hound, so although I gave an optimal range in post #3, I'll tolerate a slightly out of range coil to get surface area... either with the wrap count or diameter needed to fit the physical environment.

Don't forget the wattage adjustment (an easy "oh shit!") appropriate for the desired resistance.

Sometimes every element is perfect... and other times you have to fudge one to get another. A bit in the red or blue zones isn't a deal breaker... if you know what to expect and can accept the shortcomings.

 

[Fuzzy Bruce]

Thanks, I guess it is time to play with the steam engine site and take notes.

 

[State O' Flux]

Yep... Dampmaskin has added so many features since he went live in February that, if you're working with it for the first time... I suppose it might take awhile to familiarize yourself with all the "bells and whistles".

 

[UncleRJ]

 

[State O' Flux]

But only until the cells burn out... then it's smooth sailin'.

 

[UncleRJ]

But only until the cells burn out... then it's smooth sailin'.

Then I have been sailing SMOOTH for quite a while now

 

[Chris'sClouds]

Whats a good heat capacity for a box mod and RTA?

 

[martnargh]

Depends on which box mod and which rta. More important question is how much heat YOU and your battery can handle.

Sent from my SM-N920T using Tapatalk

 

[HondaDavidson]

Whats a good heat capacity for a box mod and RTA?

What kind of vape do you like? I like a warmish flavorful vape and vape at less than 25 watts with a tightish, but not MTL only draw. I tend to target builds to a Flux of 150-200 and capacity below 30, per coil. I use Mechanical mods so most of my build start at a heat flux in the 190-215 range with a fresh battery that will not drop much below the 150 mark when the battery is drained. If i was using a regulated mod, my guess I would probably build higher capacity and lower fluxed coils, because I would be able to BOOST the wattage to get the heat I want.

Like with the Heat flux there is no perfect number. Heat capacity is how much heat the coil can hold and transmit.. So it becomes a balance of flux and capacity. The higher the capacity the more heat the coil can transmit, also the more capacity the longer the coil will take to get hot and cool back down.

 

[Debbiej]

I think it's gonna be a different vape because you're gonna be dealing with a different surface area.
Even though the ID is the same and the ohms the same.
More surface area, more liquid on coil, more vapor from coil.

Your bug on the screen got me. I kept trying to squish it

 

[saytar]

Then I have been sailing SMOOTH for quite a while now

Me too.......................

 

[saytar]

I think it's gonna be a different vape because you're gonna be dealing with a different surface area.
Even though the ID is the same and the ohms the same.
More surface area, more liquid on coil, more vapor from coil.

Squash that damn bug! He tried to bite me....