Airflow theory

[cadcoke5]

I am bit puzzled about how airflow causes the coil to produce more visible vapor.

I know that when boiling water in a tea kettle, the heat causes some of the water to get hot enough to become an invisible gas (the true steam). That gas exits the kettle, and very soon drops enough in temperature so that it condenses into droplets we commonly call steam, but really is a vapor or fog.

E-cigs I wonder if there are other mechanisms at work here. I am at a loss to understand why airflow in any way affects vapor production. In my Phoenix atomizer, if I just allow the coil to heat and not blow, I get almost no vapor. But, as soon as there is some air flow, a lot of vapor is produced.

Can anyone explain how air flow causes the production of vapor in an E-cig?

Joe Dunfee

 

[gravewolf]

When you evaporate the juice and it gets exposed to air it cools and condenses which forms the vapor like how clouds and mist are produced....though it's okay for someone else to correct me if I am wrong. I've been building some atomizers and airflow is a big key in getting good vapors. The closer the hole to the wick and coil the better the vapor production gets. Though flavor production is just as important as the amount of vapor in an atomizer.

 

[cadcoke5]

When you evaporate the juice and it gets exposed to air it cools and condenses which forms the vapor like how clouds and mist are produced.

I would think that the liquid turns into gas as soon as it hits the hot coil. Then the gas would condense quickly into droplets that form the vapor cloud. So, my own prediction about things is that this process would continue without airflow and be like a tea kettle boiling.

As I reach for straws trying to figure out how airflow affects this, my only guess is that the vapor droplets might tend to re-fall back onto the coil rather than float away without airflow to carry them?

Joe Dunfee

 

[gravewolf]

I would think that the liquid turns into gas as soon as it hits the hot coil. Then the gas would condense quickly into droplets that form the vapor cloud. So, my own prediction about things is that this process would continue without airflow and be like a tea kettle boiling.

As I reach for straws trying to figure out how airflow affects this, my only guess is that the vapor droplets might tend to re-fall back onto the coil rather than float away without airflow to carry them?

Joe Dunfee

I doubt that the vapor droplets fall back since there are some coil builds that don't have much vapor but you can still taste the e-liquid flavor. The surest thing I know is when building an atomizer placing the airhole very near the coil would give lots of vapor.

 

[eHuman]

Joule–Thomson effect: Air passing through a throttled or reduced orifice size causes a drop in temperature. Speed of air flow and orifice size affect cooling efficiency. (greater speed, orifice shape, size and orientation affect greater cooling capicity of intake air or gas.

As you stated, just the air itself causes the gas to condense, this can be seen by removing the cap on an RBA, hitting the fire button and watching vapor billow off of your coil.

By sucking on the drip tip you create a vacuum in the air chamber, drawing air through the reduced size air hole causes a super cooling of that air entering the air chamber. Cooler air condenses the "steam" or vapor more rapidly than warmer air. The physical shape and size of the air chamber can have effects on vapor production efficiency and density, as well as the size of the orifice of the drip tip opening.

Maximum efficiency of vapor production and density can be engineered through experimenting with air chamber shape, size, drip tip and air-hole size and location relative to the coil. There is also a point of diminishing returns where too much air flow or chamber size actually reduces vapor volume/density production. "Air to fuel ratio fine tuning".

The process is similar to a supercharger on the intake of a performance motor.

Ever see the youtube video of a guy in Russia taking a pot of boiling water and throwing it off of his 4th story balcony with an outside temperature of something like -50 degrees? 100% of the water is instantly cooled and none of it touches the ground. A huge cloud of vapor is formed, very dense and just hangs in a column like a cloud in the sky.

Super cooling of heated liquid producing massive vapor clouds...

 

[gravewolf]

@eHuman

I could kiss you right now for that sweet information but since you're probably thousands of miles away from me you can relax It's true about the shape of the air chamber and also the size of the airhole. Also too much airflow results in a cold vape and a loose draw which I hate, and I've already experience this with my failed atomizer.

 

[eHuman]

It has been years since I have visited your country (I miss the awesome food). There are some very nice quality MODs and RBAs coming out of the Philippines right now, well worth keeping an eye on.

I agree with you, there are hard scientific factors that affect our quality of vape, but then like flavoring some of them become subjective to the individuals likes/dislikes. There is a balance of the variables that do cause one device to out shine another.

An example of a quality RBA that gets many of these factors balanced correctly that I can give is the Chalice by Mark Bugs
Using the same wick and coil material, wraps and Ω, same juice, same PV at the same voltage/power setting; There is a huge and noticeable difference in flavor and vapor quality between the Chalice and the IGO-L (which I happen to love and recommend, the IGO-L is by no means a slouch). The Chalice is just in a class of it's own. I think Mark did his research. The Chalice is not in a comfortable price range for most vapers, and I would not own one myself had it not been for my good fortune winning a contest with it as the prize.

 

[gravewolf]

@eHuman
I am very happy to know that you visited my country and loved our food. Yeah there are far too many variables that make a good atomizer. Even the best rba's out there can perform badly if the user isn't aware of the proper coil builds. Also the type of juice can also affect the amount of vapor whether it's whole PG, VG or a combination of both. It's really fun to figure out all these variables. I've never had the pleasure of trying out a Chalice or the IGO-L since I've only bought 2 atomizers (both were lost) and now I'm just using my own self made unit.

 

[eHuman]

The IGO-L is very inexpensive and a great dripping style atty. All SS construction.

 

[monkey13]

Joule–Thomson effect: Air passing through a throttled or reduced orifice size causes a drop in temperature. Speed of air flow and orifice size affect cooling efficiency. (greater speed, orifice shape, size and orientation affect greater cooling capicity of intake air or gas.

As you stated, just the air itself causes the gas to condense, this can be seen by removing the cap on an RBA, hitting the fire button and watching vapor billow off of your coil.

By sucking on the drip tip you create a vacuum in the air chamber, drawing air through the reduced size air hole causes a super cooling of that air entering the air chamber. Cooler air condenses the "steam" or vapor more rapidly than warmer air. The physical shape and size of the air chamber can have effects on vapor production efficiency and density, as well as the size of the orifice of the drip tip opening.

Maximum efficiency of vapor production and density can be engineered through experimenting with air chamber shape, size, drip tip and air-hole size and location relative to the coil. There is also a point of diminishing returns where too much air flow or chamber size actually reduces vapor volume/density production. "Air to fuel ratio fine tuning".

The process is similar to a supercharger on the intake of a performance motor.

Ever see the youtube video of a guy in Russia taking a pot of boiling water and throwing it off of his 4th story balcony with an outside temperature of something like -50 degrees? 100% of the water is instantly cooled and none of it touches the ground. A huge cloud of vapor is formed, very dense and just hangs in a column like a cloud in the sky.

Super cooling of heated liquid producing massive vapor clouds...

hei eHuman,

im trying to learn and understand the airflow concept/theory.

will the VP and TH be affected by the position of the airhole either being position on the top coil or bottom coil?

 

[eHuman]

hei eHuman,

im trying to learn and understand the airflow concept/theory.

will the VP and TH be affected by the position of the airhole either being position on the top coil or bottom coil?

Yes. It is better to have your air intake lower than higher in relation to the coil.

Imagine an over exaggerated example where your air hole is as high up on the cap as possible, well above the coil:
When you draw air from the tip, it enters the chamber above the coil and up to your mouth. There is no air directly passing over the coil cooling the steam and producing vapor. As the heat (non vaporized steam) builds in the chamber you will be drawing it up into your mouth. Since you are essentially inhaling steam, instead of vaporized juice, you will get a hot/harsh, vaporless TH, and you may or may not taste some of the flavor.

A carto design places the air intake below the coil so that all of the air passes by it. More cooled air across the heated coil produces more vapor. It has a constant supply of fresh cooled air as long as you are drawing on the mouth piece.

Lower air intake is better, but it doesn't have to be coming from directly underneath.

 

[cadcoke5]

Imagine an over exaggerated example where your air hole is as high up on the cap as possible,... As the heat (non vaporized steam) builds in the chamber you will be drawing it up into your mouth. Since you are essentially inhaling steam, instead of vaporized juice

I am still not convinced. If something is non-condensed steam, then its temperature is at the boiling point. In my experiments I never got gas hot enough to burn my mouth. I am convinced that the steam is very quickly condensed. (I should mention, in case a reader is not familiar with the terminology, that true water steam is invisible and is always above its boiling point. Vapor refers to the cloud that forms when the steam condenses into very tiny droplets that float in the air)

I can think of two possible differences between an
A) Airflow that hits the coil, vs.
B) Distant inlet, such as drilling a new hole at the top of a Phoenix atomizer.

There are two possible tests I would propose.

Condensed Droplet Size;
It might be that the vapor looks denser because the droplet size is smaller. This affects how dispersed the vapor gets in the mouth and airway. But, I think this is not the sort of test you can do at home without very specialized equipment. I recall reading about the use of Lasers being shot into a cloud to measure this, but I don't know how to interpret the results. We can measure opacity easy enough, but that would not be affected by droplet size alone, since the total quantity also affects this.

Quantity of Liquid Vaporized; This is the easiest to measure. Perhaps it can simply be done by measuring the Phoenix atomizer before and after a timed test with a known quantity of air. This would require a very accurate scale, which I don't have.

Joe Dunfee

 

[eHuman]

We are sort of saying the same thing, in part at least. I don't mean that the steam will burn your mouth, you are still taking in air mixed with it cooling it off. But unless the "super" cooled air (joules thomson effect) flows directly over the heated coil, vapor production efficiency is reduced. It can be mathematically proven. Similar (but for a different reason) that a blacksmith directs his bellows at the fire, not just near it.

 

[ScatRD]

Lower air intake is better, but it doesn't have to be coming from directly underneath.

No it doesn't as is the case on most RBA mods, but optimal would be so. I believe that's why the Immo produces such a thick dense vapor cloud. The air enters from the side and hits the inner wall where it has to turn down and go under the ceramic plate and enter the chamber under the wick/coil and then has a straight shot up and out the drip tip.

 

[bapgood]

sorry wrong thread