I have been wrong about air flow in RDAs all the time...

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EIHYPI

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I decided to grab my tsunami 24 plus from its shoe box because I wanted to learn to build better on it and get a nice vape. I guess I'm a little bored and want to build and vape this rda I always got wrong. My main issue coil placement together with the bottom airflow in mind. Am I supposed to have it that the coil is literally on top of the airflow channels, just not touching?
 
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MortenOen

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I decided to grab my tsunami 24 plus from its shoe box because I wanted to learn to build better on it and get a nice vape. I guess I'm a little bored and want to build and vape this rda I always got wrong. My main issue coil placement together with the bottom airflow in mind. Am I supposed to have it that the coil is literally on top of the airflow channels, just not touching?

Yes, that's the right position. If your coil is very big compared to the air hole, then mount the coil a bit higher, but still straight above the air hole. Distance does not matter for the direction of the flow.

Cheers!
 

DaveP

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MortenOen, I watched the video and found it enlightening. Thanks for posting it.

I'm wondering if there's a strong correlation between air port diameter and coil distance to determine coil height for maximum vapor production. I vape mostly Kayfuns and I've tried raising and lowering coil height, but haven't really determined which is best for vaporizing juice efficiently. Any insight you can provide will be welcome.
 
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MortenOen

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@DaveP
More important than the size of the opening, is the "depth" of it. Thicker walls or tubes will be much more directional. Just "a hole in the wall" will act like a sawed off shotgun, while a tube gives more of a rifle direction and higher speed of the flow. It's about the vector of the molecules for the first few millimeters, then the flow spreads out. The coil should never have smaller diameter than the hole. Distanse from the hole is difficult, as every air port has its own distinct sweet spot. Think more about having space around the coil, at least 1,5mm on all sides, and hit it perpendicular (air from the right side should hit the coil at 3 o'clock). These two demands will tell you the best outer diameter of the coil, and where to put it. If you see gunk on the coil after a day or so, it tells you where the cooling is bad. Then adjust half a mm at a time. Then pump up the watts till the vapor has the temperature you like :)
 

-KT-

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Hi MartinOen,

I have a velocity style deck and put the split coil right over the two bottom holes with a small but reasonable space above the holes.

It's a "single" coil on a two coil deck, so I blocked off the other side. Then I sculpted wicking to fill in all gaps except for an air channel around the coil and up to the drip tip.

Your concept of minimizing turbulence in the atty works. I've tried this with different coils and ohms. I get a lot of flavor and no gurgling or popping, even with the coil and wick absolutely saturated.

Thank you for your hard work and research!
166324c93331816847ded747e59717af.jpg


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MortenOen

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Hi MartinOen,

I have a velocity style deck and put the split coil right over the two bottom holes with a small but reasonable space above the holes.

It's a "single" coil on a two coil deck, so I blocked off the other side. Then I sculpted wicking to fill in all gaps except for an air channel around the coil and up to the drip tip.

Your concept of minimizing turbulence in the atty works. I've tried this with different coils and ohms. I get a lot of flavor and no gurgling or popping, even with the coil and wick absolutely saturated.

Thank you for your hard work and research!
166324c93331816847ded747e59717af.jpg


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That looks just awesome! Perfect!
 

-KT-

Senior Member
Oct 12, 2017
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That looks just awesome! Perfect!

Thank you!

Question:

Is there also a laminar flow effect going on when we vape?

In other words, your research showed conclusively that the Coanda effect can be encouraged by correct coil placement, build, wicking, etc.

But would laminar flow also be a factor? I have not watched all of your videos, so you may have already touched on this. Or perhaps laminar flow is part of Coanda anyway?

My intuition is that we should be aiming for laminar flow as well as Coanda?

I have some layperson knowledge of this stuff because my father was a private pilot and I used to fly with him in his small airplane, and I could literally see how air moved over the wings (when we flew through rain or clouds, mostly).

Much respect,

KT
 
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MortenOen

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Thank you!

Question:

Is there also a laminar flow effect going on when we vape?

In other words, your research showed conclusively that the Coanda effect can be encouraged by correct coil placement, build, wicking, etc.

But would laminar flow also be a factor? I have not watched all of your videos, so you may have already touched on this. Or perhaps laminar flow is part of Coanda anyway?

My intuition is that we should be aiming for laminar flow as well as Coanda?

I have some layperson knowledge of this stuff because my father was a private pilot and I used to fly with him in his small airplane, and I could literally see how air moved over the wings (when we flew through rain or clouds, mostly).

Much respect,

KT

I have pondered this very question, and I made a video on it that has turned out to be, shall we say, controversal :)
It all has to do with speed and thermodynamics. A laminar boundary layer is exelent for lift and flying, a turbulent boundary layer is better for cooling. One would therefore think that clapton coils are better for cooling. But below 25 mph, the speed at which we vape, a turbulent boundary layer leaves the coil like the wake from a boat, while the laminar boundary layer around a plain wire/ flat wire follows the Coanda effect. If you have half an hour, this will explain it:
 

-KT-

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Oct 12, 2017
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I have pondered this very question, and I made a video on it that has turned out to be, shall we say, controversal :)
It all has to do with speed and thermodynamics. A laminar boundary layer is exelent for lift and flying, a turbulent boundary layer is better for cooling. One would therefore think that clapton coils are better for cooling. But below 25 mph, the speed at which we vape, a turbulent boundary layer leaves the coil like the wake from a boat, while the laminar boundary layer around a plain wire/ flat wire follows the Coanda effect. If you have half an hour, this will explain it:


Interesting!

I agree that a lot of this stuff has not been studied at the lower air velocities typical of vaping. It might be interesting to experiment with velocity?

Here is a way to measure:

http://a.co/9jYdKbw

As you know, you can increase velocity (using the same vacuum) by making the side holes in the box, smaller.

It's possible that when people cloud-chase, for example - that they are doing fairly high velocity draws?

If I had to guess (LOL, since I pretty much have to guess) - I would guess that the "v-shaped wake" that you saw with the stapled clapton mockup would revert to more of a coanda-type flow - but only at (much?) higher velocities. I don't know the correct terminology, but I think the air has to be flowing fast enough to cause a fairly significant area of low pressure behind the coil. This low-pressure area would pull the "v" back behind the coil.

Also - now that I am thinking about things I know nothing about (and I do that often) - it occurred to me that even though we might be "intaking" air at 25mph - the actual flow velocity into the coil could be orders of magnitude higher in velocity. This is because we are intaking through an 8mm or 5mm hole - but the vent intake holes in the decks are much smaller.

Here is a way to estimate:

Calculator: Air Flow Rate through an Orifice | TLV - A Steam Specialist Company (International)

It totally can't do math! So the following formula is greek to me.

Screen Shot 2017-11-15 at 16.14.22.png


ETA - I just realized the above still only figures out rate. I think velocity can be determined from rate, but I don't know the math.

Laws of compressed air
 
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MortenOen

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Interesting!

I agree that a lot of this stuff has not been studied at the lower air velocities typical of vaping. It might be interesting to experiment with velocity?

Here is a way to measure:

http://a.co/9jYdKbw

As you know, you can increase velocity (using the same vacuum) by making the side holes in the box, smaller.

It's possible that when people cloud-chase, for example - that they are doing fairly high velocity draws?

If I had to guess (LOL, since I pretty much have to guess) - I would guess that the "v-shaped wake" that you saw with the stapled clapton mockup would revert to more of a coanda-type flow - but only at (much?) higher velocities. I don't know the correct terminology, but I think the air has to be flowing fast enough to cause a fairly significant area of low pressure behind the coil. This low-pressure area would pull the "v" back behind the coil.

Also - now that I am thinking about things I know nothing about (and I do that often) - it occurred to me that even though we might be "intaking" air at 25mph - the actual flow velocity into the coil could be orders of magnitude higher in velocity. This is because we are intaking through an 8mm or 5mm hole - but the vent intake holes in the decks are much smaller.

Here is a way to estimate:

Calculator: Air Flow Rate through an Orifice | TLV - A Steam Specialist Company (International)

It totally can't do math! So the following formula is greek to me.

View attachment 700473

ETA - I just realized the above still only figures out rate. I think velocity can be determined from rate, but I don't know the math.

Laws of compressed air

You are very right in your logic. Study the aerodynamics of tennsiballs, baseballs and golfballs. At speeds of 55-300 mph, a golfball has much less drag than a similar ball without dimples. Above 300 mph, the smooth ball is much better than the dimpled golfball. All the science I have read says that BELOW 55 mph, dimples or not, does not matter for the sparation points. The air goes all the way around because of Coanda effect. I'll bet they never put golfballs in wind tunnels at 20 mph. My research has proven that at slow speeds, a cylinder with a trip wire causes separation immediatly.

I agree that I know nothing about the velocity that actually is hitting the coil, it's total guesstimation. But seeing that you have separation points even with just slightly uneven coil, suggests that the speeds in an RDA-like environment is very slow. You could argue that it's actually fast, but the coil with trip wire proves that the speed in the chamber and around the coil is indeed slow.

I have experimented with different openings, but speed when you inhale is limited to the low presure you can create with your lungs. No matter how hard I inhale through straws, it always goes 4-6 seconds before my lungs are full. If I could fill my lungs in an instant, the speed would indeed increase dramatically, but I think our muscles are the limiting factor here (diaphragm and inter costal).

Like you I don't understand anything of the formula. But then again, the Coanda effect is known only through experiments, not proven with theoretical physics. That is what I have been told. So seeing is beliving :) This stuff is getting far too serious for me....
 

-KT-

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Oct 12, 2017
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You are very right in your logic. Study the aerodynamics of tennsiballs, baseballs and golfballs. At speeds of 55-300 mph, a golfball has much less drag than a similar ball without dimples. Above 300 mph, the smooth ball is much better than the dimpled golfball. All the science I have read says that BELOW 55 mph, dimples or not, does not matter for the sparation points. The air goes all the way around because of Coanda effect. I'll bet they never put golfballs in wind tunnels at 20 mph. My research has proven that at slow speeds, a cylinder with a trip wire causes separation immediatly.

I agree that I know nothing about the velocity that actually is hitting the coil, it's total guesstimation. But seeing that you have separation points even with just slightly uneven coil, suggests that the speeds in an RDA-like environment is very slow. You could argue that it's actually fast, but the coil with trip wire proves that the speed in the chamber and around the coil is indeed slow.

I have experimented with different openings, but speed when you inhale is limited to the low presure you can create with your lungs. No matter how hard I inhale through straws, it always goes 4-6 seconds before my lungs are full. If I could fill my lungs in an instant, the speed would indeed increase dramatically, but I think our muscles are the limiting factor here (diaphragm and inter costal).

Like you I don't understand anything of the formula. But then again, the Coanda effect is known only through experiments, not proven with theoretical physics. That is what I have been told. So seeing is beliving :) This stuff is getting far too serious for me....
Agreed on all of the above.

I am wondering if heat is a factor as well?

That is, even with the "rough coils" not showing the dimpled golf ball effect - perhaps the heated vapor is creating a quasi slippery air layer (and thus mimicking a smoother surface?)

I don't recall the name for this effect, but it's seen when one drops a little water in a hot fry pan. For an instant before evaporation, the water floats on a slippery layer of super-heated steam.



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Just Me

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I don't recall the name for this effect, but it's seen when one drops a little water in a hot fry pan. For an instant before evaporation, the water floats on a slippery layer of super-heated steam.

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Leidenfrost effect is what you're describing about the water droplets dancing in a hot pan. That's a cooking thing. I don't really know if that applies with vaping. (Insert "shoulder shrug" or "clueless" smiley here.)
 

-KT-

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Oct 12, 2017
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Leidenfrost effect is what you're describing about the water droplets dancing in a hot pan. That's a cooking thing. I don't really know if that applies with vaping. (Insert "shoulder shrug" or "clueless" smiley here.)
Thank you.

Yes - agreed.

I'm totally intrigued by theories as to why a complex coil might work better than a simple coil. I know that there is more surface area, and like Oen, I expected to see better aerodynamics.

But if the aerodynamics are worse at at least room temperature, perhaps the coil heat itself is having an effect?

I'm shrugging my shoulders too, LOL.

ETA - just scanned this:

https://www.google.com/url?sa=t&sou...WCDcQFghAMAM&usg=AOvVaw0f4HlIcK-pMab6BTAHNGWF


It appears possible that the leidenfrost effect itself may be allowing small droplets of vapor to move around on the coil?
37d9e1124878c1b065cd14f1001e9b00.jpg


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Just Me

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Thank you.

Yes - agreed.

I'm totally intrigued by theories as to why a complex coil might work better than a simple coil. I know that there is more surface area, and like Oen, I expected to see better aerodynamics.

But if the aerodynamics are worse at at least room temperature, perhaps the coil heat itself is having an effect?

I'm shrugging my shoulders too, LOL.

ETA - just scanned this:

https://www.google.com/url?sa=t&source=web&rct=j&url=https://www.pmmh.espci.fr/fr/gouttes/Publications_files/Aerodynamic%20Leidenfrost.pdf&ved=0ahUKEwjmoZX2k8LXAhVmwYMKHdzWCDcQFghAMAM&usg=AOvVaw0f4HlIcK-pMab6BTAHNGWF


It appears possible that the leidenfrost effect itself may be allowing small droplets of vapor to move around on the coil?
37d9e1124878c1b065cd14f1001e9b00.jpg


Sent from my R1 HD using Tapatalk

I don't make complex coils, and I'm not really interested in the science of it. I just know I've been cigarette/tar free for 4 1/2 years, and I'm really good with that.

I'm really critical about food preparation, but not so much about vaping. As long as I'm not smoking, all is well.

Good luck figuring out the coil details that work for you.
 

-KT-

Senior Member
Oct 12, 2017
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I don't make complex coils, and I'm not really interested in the science of it. I just know I've been cigarette/tar free for 4 1/2 years, and I'm really good with that.

I'm really critical about food preparation, but not so much about vaping. As long as I'm not smoking, all is well.

Good luck figuring out the coil details that work for you.
Yes. The only thing I am super critical about re: vaping is making sure everything is clean (including my hands), when I make coils.

LOL - learned that the hard way!

That's awesome on being free from cigs!

I've now been clean from cigs for a few weeks. Part of what got me interested in the technical aspects is literally nicotine delivery. I'm trying to hit a sweet spot where I get a nice hit of nic, AND flavor and clouds. Not clouds for their own sake (although that is sometimes fun) -

Rather - I have noticed that I tend to prefer super dense vapor. This is why the Coanda Effect is so important. To get max vapor, air and juice need to meet each other.

When I first started vaping a couple of months ago, I bought a kit with a tank that uses drop in coils. I could never get things the way I wanted them. I had a lot of problems with dry hits on one end and popping/gurgling on the other.

Then I studied up on RBAs and the like and realized that it's not super hard to make simple coils.

Then I started studying wicking strategies and realized that even wicking can have large effects on air flow. And thus flavor.

So after probably at least 80 hours of just kind of reading, watching videos, scanning threads here and other places - AND most importantly, experimenting - I got to a point where I am getting good rich vapor at 40 to 50 watts with various single coil builds.

It seems to involve coils (of any type) that are around 25 to 40mm ID, 7 to 10 wraps (depending on wire resistance) and actual resistance between .5 to .6 ohms. Wire diameter or type just isn't having large effects. That is what is confusing to me.

I've built numerous coils by this point. Macro, micro, tornado shaped, twisted, etc. I even bought some pre-made aliens.

The largest effects I am getting are achieved by staying in that ohm range, staying single coil, and making sure I wick so that air can ONLY pass over the coil.

The "type" of coil isn't having large effects.

Anyways - that is why this is all interesting to me. There's something going on that is outside of what we currently know about.

It's not explained.

"By knowing things that exist, you can know that which does not exist."

-- Miyamoto Musashi

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