TENSE ABOUT SMALL COILS

[Templar1191]

Smaller coils or bigger coils? This is the question

I was playing CSGO and my mind began to wander. I had been experiencing better performance from narrower diameter coils. I could not imagine why. Surely a 3mm diameter coil would out perform a 1.5mm coil across the board because you can soak it more.

Totally wrong. Why? surface tension. When you have water in a bottle or bucket, or just water drops, they form certain curves around the face/edge of the surface they are in or on. Water drops, because of surface tension. Lake skating insects. The surface is under tension to find the most stable arrangement of molecules.

This meniscus as it is known is almost independent of the size of the bulk body. Eg, the meniscus or curvature of the water with the wall at the water line will be the same as the curvature in a small glass of water.

Thus, while a larger coil can soak more, the meniscus/surface tension radius of the narrower coil will hold more fluid around the coils because the coil "cylinder" is of much smaller radius.

TL;DR narrower coil diameters reduce the storage capacity for RDA's, but actually keep the wick and coils cleaner for longer by keeping more fluid in contact with the coil.

 

[Boden]

While lyrical, you may want to reexamine the physics involved.

 

[Templar1191]

If you have a better theory lets hear it

 

[Boden]

If you have a better theory lets hear it

About what?

How the pg/vg ratio changes the surface tension and boiling point of juice?

How temperature of a liquid effects the molecular tension?

How smaller coils generally run hotter because they have less area than a larger diameter coil of the same width?

How smaller coils have a lower drag coefficient so the side of the coil away from the air port doesn't overheat and cook juice on the coil?

I'm happy to help, I'm just not sure what you are referring to.

 

[SLIPPY_EEL]

There are way to many variables involved to state that one is better than the other, you have:-
Atty size
Airhole size
Length of pull
Power
Wire + contact/non-contact?
Wick + not everyone wicks the same
Juice %
Then you have opinions like for eg on a certain atty Boden thinks 4mm id coils are best and i say its 2.5mm.

 

[Boden]

There are way to many variables involved to state that one is better than the other, you have:-
Atty size
Airhole size
Length of pull
Power
Wire + contact/non-contact?
Wick + not everyone wicks the same
Juice %
Then you have opinions like for eg on a certain atty Boden thinks 4mm id coils are best and i say its 2.5mm.

I have no preference for coil size. I build to the atty. Mostly 2.3-2.7mm. The wide 4mm Radiator is a comp coil built for really high power applications.

 

[mightymen]

I use to do 2.5 - 2.75 mm coils until one day I noticed improved flavor and wicking with 2.0 mm coils. Since then I only do 2.00mm. The reason I always did 2.5 - 2.75 mm coils, always thought more was better but in my case not so.

The only disadvantage I've found when making 2.0 mm coils more turns are needed which increases the length.

 

[Boden]

I use to do 2.5 - 2.75 mm coils until one day I noticed improved flavor and wicking with 2.0 mm coils. Since then I only do 2.00mm. The reason I always did 2.5 - 2.75 mm coils, always thought more was better but in my case not so.

The only disadvantage I've found when making 2.0 mm coils more turns are needed which increases the length.

I have a general guideline that the width of a coil should not be much greater than 2x the ID. When I've gone to 3x the ID the middle of the coil can't feed fast enough and can burn through the cotton.

So a 2mm ID X 4-5mm wide coil is about the limit for that ID. 4mm being on the safe side.

If I need to build a coil that is 8mm wide I'll make the ID 3.5-4mm. Etc.

 

[mightymen]

I have a general guideline that the width of a coil should not be much greater than 2x the ID. When I've gone to 3x the ID the middle of the coil can't feed fast enough and can burn through the cotton.

So a 2mm ID X 4-5mm wide coil is about the limit for that ID. 4mm being on the safe side.

If I need to build a coil that is 8mm wide I'll make the ID 3.5-4mm. Etc.

Temperature control when set right is not suppose to burn cotton. That's one of the advantages of using TC - eliminates dry hits. I do not get burnt cotton or dry hits in TC.

 

[Boden]

Temperature control when set right is not suppose to burn cotton. That's one of the advantages of using TC - eliminates dry hits. I do not get burnt cotton or dry hits in TC.

True, but even with TC I like to keep the center of the coil well supplied.

 

[mightymen]

True, but even with TC I like to keep the center of the coil well supplied.

In other words your willing to burn you're cotton - if am understanding you right?

IMO: The trick is keeping the cotton wet enough so the temperature dissipates evenly across the coil from center to outside. Am no expert.

 

[Templar1191]

Alright Mr Chemist, get those guns out, lets do this.

How the pg/vg ratio changes the surface tension and boiling point of juice?
How is this relevant?If we take the same fluid and put it on a 1.5mm and 3mm coil, this doesnt matter. How is the boiling point relevant either; im talking about keeping the coil as moist as possible. Does the size of the coil effect the boiling point? Not if the juices are the same

How temperature of a liquid effects the molecular tension?
Molecular tension? What is molecular tension? You mean strength of intermolecular attraction and interaction, right? Obviously the viscosity and contact angles will change with temperature, but that's not the question here. The question is...
Is surface tension, viscosity or intermolecular attraction a function of the size of the "container" at coil diameters larger than 1mm? The answer is no, for reasons outlined in my first post.

How smaller coils generally run hotter because they have less area than a larger diameter coil of the same width?
Oh hreally? Tell me, if I get a 50cm or 500cm pan, fill both with de-I water and bring it to the boil at standard pressure, is the smaller one going to run hotter or cooler while it has water in it?
I think you mean they'll heat up faster because they have a disproportionately smaller volume to when compared to a larger coil, eg
1.5mm diam 8mm long coil is 14mm cubed and 41mm^2 surface area. 3mm 8mm long coil is 56mm cubed and 90mm^2. The volume does not increase linearly with coil diameter. However, the surface area is approximately proportional to diameter. So the only thing that should be effected is the thermal mass and the amount of fluid that can be held in the coil. Also not relevant here.

How smaller coils have a lower drag coefficient so the side of the coil away from the air port doesn't overheat and cook juice on the coil?
We cant comment on this without testing it. If you had any education in fluid dynamics you would know this.
L̶e̶t̶s̶ ̶d̶o̶ ̶a̶ ̶q̶u̶i̶c̶k̶ ̶c̶a̶l̶c̶u̶l̶a̶t̶i̶o̶n̶ ̶t̶o̶ ̶a̶p̶p̶r̶o̶x̶i̶m̶a̶t̶e̶ ̶w̶h̶a̶t̶ ̶f̶l̶o̶w̶ ̶r̶e̶g̶i̶m̶e̶ ̶w̶e̶ ̶a̶r̶e̶ ̶i̶n̶ ̶t̶h̶o̶u̶g̶h̶.̶ ̶
Oh wait, I dont have a flow meter small enough to fit on my RDA's and tidal volume is completely arbitrary when huffing e-cigs.
Did you know that boundary layer thickness on objects in flow streams does not scale linearly with object size?
I'm not going to dig super far into this, but drag coefficient is sufficiently static with solid spheres that it is ok for drag force calculations to use the same C_d for a 5cm sphere vs a 10cm sphere.
But to further shut down this argument, tell me why a 20 micron sized sphere of aluminium can remain airborne for magnitudes longer than a 1cm diameter aluminium shot. PS its not because of brownian motion.

Smaller coils will have the same drag coefficient as larger coils, or will be larger. In this case, I doubt the drag coefficient makes any difference at 1.5 vs 3mm but I cannot be certain without testing it.

I'm happy to help, I'm just not sure what you are referring to.
If you were truly here to help, you would have just said your second post first, instead of walking into the thread just to say someone is wrong. Back to Le Reddit with your stale meme DP
In the mean time, I'll be under my bridge.

 

[Templar1191]

Does anyone here know the thermal conductivity of PG/VG soaked cotton/rayon? No?
Ok heres another question, will the thermal resistance (resistance to heat transfer) be significantly greater on a 1.5mm vs 3mm coil?

Ok, how about the mass transfer rate via diffusion through the wetted cellulose? Will this be a rate limiting step when it comes to keeping the metal coil coated with sufficient fluid?

Your cellulose shouldnt be burning. I never burn my cellulose because I keep everything filled up or wet. What will be happening though, is that your high VG fluid will be reacting with oxygen and decomposing above 200C. It will probably be happening above 100C too, but the rate of reaction between 100-200C will obviously be lower than 200-300C. Flavouring esters, I would guess they will also be susceptible to oxidation and reaction. I have no GC MS results to back this up though.

Here's something I didnt look into properly before. Is the trend for dynamic viscosity of VG different to that of PG with respect to temp? Eg, will the viscosity wrt temperature curve be different for 50/50 vs 70/30 VG/PG? I had a look but what few charts I could find didnt seem to match up to any degree. Glycerol and PG have very similar exponential type curves for dyn. visc. wrt temp.

Boden you should read some of my other posts and educate yourself. I'm always happy to help.

 

[sonicbomb]

You don't need a degree in physics or chemical engineering to get a good vape, but it might help. I'll get my popcorn if there's going to be a science-off

 

[SLIPPY_EEL]

The great flavour that everyone witnesses with smaller 'id' coils is due to the ability of the coil being able to vaporize not just the the juice sat in the layer around the core of the wick but being able to vaporize the Whole wick inside the coil.

 

[Templar1191]

All i need is a small loan of 1 million dollar

 

[Templar1191]

I believe there may be greater fractionation with larger coils. This is very annoying as all my tanks are running 3mm inside diameter coils with 6-8 wraps on each. I think this is affecting flavour badly.

Theyre all claptons too.grr

What i mean by fractionation is separation of vapours based on boiling point and volatility. So i think larger coil will encourage more pg and nicotine while dulling the flavour.

On the other hand it does mean less fouling of fluid and longer wick life. Hmm