Attention manufacturers!! AFC rings are the wrong way to reduce airflow.

[Boden]

In order to keep the air flowing over the coil at high enough speeds you need to have a variable aperture air port pointing at the coil. Reducing the airflow at the AFC ring only slows the velocity of air over the coil. Reducing the diameter of the air port pointing at the coil allows the draw to be tighter and keeps the air velocity high enough to work properly.

Whether this is done with inserts or something fancy like a variable aperture does not matter!!

 

[Matty316]

True, but I can see it being quite difficult engineering one or more adjustable internal apertures. Probably why it hasn't been done yet.

I agree with you 100% though and it would be great if someone managed too.

 

[David Wolf]

In order to keep the air flowing over the coil at high enough speeds you need to have a variable aperture air port pointing at the coil. Reducing the airflow at the AFC ring only slows the velocity of air over the coil. Reducing the diameter of the air port pointing at the coil allows the draw to be tighter and keeps the air velocity high enough to work properly.

Whether this is done with inserts or something fancy like a variable aperture does not matter!!

I need to think about this one. Agree that velocity is important, but so is volume of air flowing around the coil. Initial thoughts are its a balance, a tiny air hole won't allow enough volume to cool the coil, too much won't provide good density and flavor. Your point about the flow being directed to the coil (instead of wasted flow by the coil in the case of horizontal coils) seems logical.

 

[Matty316]

I need to think about this one. Agree that velocity is important, but so is volume of air flowing around the coil. Initial thoughts are its a balance, a tiny air hole won't allow enough volume to cool the coil, too much won't provide good density and flavor. Your point about the flow being directed to the coil (instead of wasted flow by the coil in the case of horizontal coils) seems logical.

Depends on the build and watts used with say a 24G build run at high watts you going to need a greater voume of air passing over the coil to keep things cool but with say a 30G build you don't need as high a volume of air passing over the coil. If anything too much air can be counter productive. But in both cases the velocity of the air passing over the coil is important and with afc rings that volocity is lost because the bottleneck is too far from the coil.

 

[Boden]

I need to think about this one. Agree that velocity is important, but so is volume of air flowing around the coil. Initial thoughts are its a balance, a tiny air hole won't allow enough volume to cool the coil, too much won't provide good density and flavor. Your point about the flow being directed to the coil (instead of wasted flow by the coil in the case of horizontal coils) seems logical.

Of course as the port is reduced the coil size needs to be adjusted accordingly.

 

[Boden]

Depends on the build and watts used with say a 24G build run at high watts you going to need a greater voume of air passing over the coil to keep things cool but with say a 30G build you don't need as high a volume of air passing over the coil. If anything too much air can be counter productive. But in both cases the velocity of the air passing over the coil is important and with afc rings that volocity is lost because the bottleneck is too far from the coil.

Wire guage does not matter. It's the size of the coil (ID and width) that must match the port pointing at it.

Exactly, The restriction should be directly underneath the coil

 

[AndriaD]

In order to keep the air flowing over the coil at high enough speeds you need to have a variable aperture air port pointing at the coil. Reducing the airflow at the AFC ring only slows the velocity of air over the coil. Reducing the diameter of the air port pointing at the coil allows the draw to be tighter and keeps the air velocity high enough to work properly.

Whether this is done with inserts or something fancy like a variable aperture does not matter!!

I think this is probably why the airflow on my Achilles RDAs suits me right down to the ground, because the aperture under the coil is so very tiny. The new Achilles 2 has a slightly larger aperture, so I don't know if it will suit me at all, though early reviews in the Achilles thread indicate that it can be closed down to the same airflow as the original Achilles. I'll have to wait for the clones though, no way I can afford the authentics, especially since I don't know if that larger aperture will suit me at all.

Andria

 

[Boden]

I think this is probably why the airflow on my Achilles RDAs suits me right down to the ground, because the aperture under the coil is so very tiny. The new Achilles 2 has a slightly larger aperture, so I don't know if it will suit me at all, though early reviews in the Achilles thread indicate that it can be closed down to the same airflow as the original Achilles. I'll have to wait for the clones though, no way I can afford the authentics, especially since I don't know if that larger aperture will suit me at all.

Andria

The Achillies is the perfect atty for screw-in inserts. It could come with three diferent air nozzles 1mm, 1.5mm, 2mm for example. Threaded at the base so you could balance the power and airflow.

 

[Bunnykiller]

I think Mr. Bernoulli might see it differently

 

[Boden]

I think Mr. Bernoulli might see it differently

This i gotta see...

What do you think Bernoulli's principle has to do with this that we don't already deal with?

 

[David Wolf]

Haha well it would be helpful to know which tank were talking about. I will say this, for a design that has an air flow path coming from the bottom, doesn't matter how far below the coil the restriction is, the pressure drop will be the same for a given suction at the drip tip therefore the flow rate would be the same. The flow rate will be higher at the restriction and lower on either side of the restriction. Now the flow turbulence near the coil however will be impacted by the location of the restriction. A nautilus mini is what I have in mind for this discussion.

 

[roxynoodle]

Goblin Mini. That's exactly how it works. You can open or close the opening(s) under your coil(s).

 

[roxynoodle]

Also check out the Flash e Vapor. You screw in inserts to change the size of the airhole. Or run without one at all for a very airy vape.

 

[Boden]

Haha well it would be helpful to know which tank were talking about. I will say this, for a design that has an air flow path coming from the bottom, doesn't matter how far below the coil the restriction is, the pressure drop will be the same for a given suction at the drip tip therefore the flow rate would be the same. The flow rate will be higher at the restriction and lower on either side of the restriction. Now the flow turbulence near the coil however will be impacted by the location of the restriction. A nautilus mini is what I have in mind for this discussion.

With the Nautilus Mini the coil head is the restriction/ high velocity point. This is good.

I am refering to RTA's whuch have an air port pointing at the coil. Having the point of high velocity all the way down at the AFC is a design flaw.

The faster the air hitting the coil is moving the better so put the restriction as close to the coil as possible.

 

[Boden]

Goblin Mini. That's exactly how it works. You can open or close the opening(s) under your coil(s).

Not qiite, the air velocity slows after the restriction quite quickly. It would be better if the restriction was closer to the coil.

 

[roxynoodle]

But its right beneath the coil. I don't know how much closer it could get. A good portion of the base is open so its not restricted by much coming under the deck. I see it as a genius design for an RTA that can be very tight and small chambered for single coil m2l or run wide open and dual coiled.

 

[Douggro]

I get Boden's argument. Never took Applied Physics but I think there are some other issues involved, in that the flow through the coil opening isn't usually a non-turbulent, laminar flow. Like many things engineered, seems to me that airflow rings are a compromise of simplicity of function over absolute effectiveness of function.

 

[Boden]

But its right beneath the coil. I don't know how much closer it could get. A good portion of the base is open so its not restricted by much coming under the deck. I see it as a genius design for an RTA that can be very tight and small chambered for single coil m2l or run wide open and dual coiled.

I agree its a simple design. Quite elegant.

I'm trying to make a simple point.
It would be better if they did away with the variable AFC ring and included inserts that closed down the air ports under the coils if someone wanted a tighter draw.

 

[roxynoodle]

I think the Goblin Mini is the closest you're going to find currently.

 

[Boden]

I get Boden's argument. Never took Applied Physics but I think there are some other issues involved, in that the flow through the coil opening isn't usually a non-turbulent, laminar flow. Like many things engineered, seems to me that airflow rings are a compromise of simplicity of function over absolute effectiveness of function.

Yes

There is another more complex function. The coil should be in a high velocity low pressure zone vs a low velocity high pressure area. This would increase evaporation rate around the coil. Also as the air velocity drops and the air pressure rises the vapor condensation rate would increase leading to a more saturated vape.