Watts do not matter. Its all about wire temp. Read on

[jjkillian]

Okay, simple little test using a dual coil set up that I have. 28G Kanthal at .4 ohms.

For now, this temp is just a base line. No settings are done on my part to adjust for certain parameters. However, it should be fairly close.

The file created with these short vids are almost 1 gig each. That is how much data is being pumped in to the video. It is a pretty high rez imager at 640x480. So I just recorded my screen with my phone to show, for now.

Here is an image with two radiometric lines across both coils. Talk about total luck to get these two so close.



Video links:

http://www.youtube.com/watch?feature=player_detailpage&v=KfRZijKgJOU

http://youtu.be/MKmSq6tqf6g

 

[Mad Scientist]

I have only seen Temperature/Amp tables for Nichrome. Is it available for Kanthal?

Also those Nichrome tables are for straight wire only, not coils. coils are estimated to require half the specified amperage for the temp. But there is no definition as to what a coil is: diameter or pitch.

I think the curve in air, regardless of coil shape, etc. will rise sharply until the heat added reaches equilibrium with heat transferred to the air (or the wire melts). I'm not sure that gives us much knowledge. In air, a coil will heat faster and get hotter than a straight wire, and the specific shape will change its characteristics, but modeling atomizer performance from performance in air is just a rough guess and the proposed precise measurements are really overkill.

Coil performance in air has been studied. Heaters made from resistance wire are made this way. The most efficient loop spacing is 3 to 6 wire diameters; I can't remember coil diameter but its irrelevant be ause it's all done in air.

 

[jjkillian]

For those of you that have read the Mundys Magic Wire thread. Here is one in operation.



539.8F was the highest observed temp.

 

[gdeal]

Great info!

Did you record the power levels being put through the 28g wire?

Also what was the resistance and power level for Mundy's wire?

For those of you that have read the Mundys Magic Wire thread. Here is one in operation.

View attachment 265873

539.8F was the highest observed temp.

 

[jjkillian]

Just goofing off so far.

It was on a mech device. Battery was not fully charged by a long shot. Guessing 3.3V or so at the coil. Battery probably in the 3.8 range.

On the Mundys coil, it is .5 ohms. .8mm x .1mm spun and wrapped the Mundy way.

 

[jjkillian]

Here is it "tuned" and also in red/blue which most people prefer

 

[Mad Scientist]

It is definitely very interesting but if anyone can draw useful conclusions from this, I'd be interested to know what they are.

 

[jjkillian]

It is definitely very interesting but if anyone can draw useful conclusions from this, I'd be interested to know what they are.

Cant really do anything with this stuff yet. I will set up something simple for the different sizes of Kanthal then we will go from there.

 

[cadcoke5]

It is definitely very interesting but if anyone can draw useful conclusions from this, I'd be interested to know what they are.

That is a very good point to raise. Knowing the temperature is not helpful information by itself. It may be a way to see how different coil geometries affect temperature, but even that is just abstract data. It is the end results that must be compared to the various readings, and hopefully use that information to guide the e-cig designer towards a better end result.

I imagine the quantity of juice vaporized is one measurement that can be made. Other things that might be measured such as the vapor's particle size, or density, those are not easy to measure without specialized equipment. Air flow is another variable that is known to dramatically affect the quantity of juice vaporized.

It may not be too difficult to measure the weight of a drip atomizer before and after a test. But, the air flow is a more difficult item to settle on. What is a standard air flow? What is the starting temperature and humidity of the air?

An entirely different sort of thing would be the flavor, which might be affected by how it gets cooked by the temperature. There is no gauge to read that particular quality.

This measurement stuff is a lot more complicated than I initially thought. What is the most useful "low-hanging fruit"? I.e. what is easy to do, and will create a useful set of data?

-Joe Dunfee

 

[dr g]

I would like to know the range of coil temperatures found in a working coil. Meaning one that is firing and producing vapor, AND being drawn from.
Not sure how you would observe that though.

 

[SeaNap]

A huge factor that has been passed over in this thread is Time. I'm not talking about the length of your draw, I'm talking about the time it takes for the coil to reach a vapor producing temperature and the time it takes for the ejuice to change states.

The wire will have its own coefficient for the amount of time it takes to raise to a certain temperature inorder to vape. I would love to figure out what temp/time this happens. Once the coil has heated to this temp it will plateau as long as there is a constant and sufficient liquid and air presence. When the plateau stage is reached there is a critical time element of how fast the liquid vaporizes, which is determined by watts. A watt is a rate of the heat required to raise the temperature of 1 g of water by 0.24 K (aka Joule) per second. Using some googlefu PG vaporizes at 914 Joules/gram. Since clearly not all of the watts are being consumed by the coil (because its not red hot) the remainder of the watts are used to convert the liquid into vapor. The more watts, the faster this reaction occers. The faster the liquid becomes vapor means the more energy present. The more energy means the warmer the vape.

Now in regards to flavor, I feel that the burnt taste that you get is a result more of the PG rapidly evaporating and leaving behind the flavor particles which will then burn as the coil heats up due to reduced liquid. This also causes the wick to burn (well at least in my case, i use cotton). This is a direct result of the watts-per-surface area. Thinner awg has a higher watts/surface area than the thicker awg.

Correct me if I'm wrong but there seems to be a distinction between what our vapor is vs the actual boiling point of PG. Our vapor is very tiny drops of liquid, whereas if you were to rappedly boil flavored ejuice the PG would dissipate as steam leaving behind the flavor particles.

This thread has progressed a lot, and what I would like to know is at what temp the coil reaches its temp plateau. Obvioulsly there are a huge amount of variables to contend with. A start would be to run the test using the same atomizer, with a very specific air intake hole, and by useing just straight 0mg PG, then varying the juice to say 6mg 80/20 PGVD no flavoring. Then vary the air hole, one way to do this is by using a selector ring like pdib made. In order to be able to capture this on camera you may need to build a glass box atomizer. Anyway, Rock On JJ! I love the thermal equipment your using, and the whole Idea of know the exact temps!

 

[jjkillian]

Testing with a draw brings in some new, and very hard to overcome challenges. First and foremost is I need line of site for the camera to work. IR doesn't "see through" anything. It picks up IR energy via the three forms of heat transfer (convection, radiation and/or conduction). The huge misconception with IR is that it can see through things, like walls. Yes I can see the studs and or missing insulation within a wall cavity, but that isn't what I am truly seeing. What I am actually seeing is the heat transfer from one side of the wall to the other and the Delta Ts associated with that. If someone had zero clue how a wall was built they would see nothing, because it isn't recognizable through familiarity of the structure. However, most of us know there are studs in the wall and because the studs transfer heat at a different rate than the other wall components to the surface (usually drywall) we can tell where the studs are.

Okay, so the point is, I need line of site. So then comes the obvious change in our application to get that line of site through the atomizer cap....just make one out of glass. Unfortunately, most of the IR equipment you see on the market cannot see through glass. Glass is opaque in the long wave of IR (7µm to 15µm approx). There are shortwave imagers around that at approx 3.5µm can see through glass. However I do not own one and they go for $50k+. There are plastics I can see through, but all would melt under the heat we are generating. That leaves us with some very specific and sometimes exotic materials they use in IR windows. None of which are affordable or easy to make, let alone made into an atomizer cap.

So that would then bring us back to heat transfer to the exterior of the caps we already have. Going back to my original train of thought......I could run tests on different wire materials then types. From that I can find the heat transfer to the cap and have a very educated guess of the coil temp. The main issue there is we are going to yield temp peaks and not "live" temps per say.

At the end of the day, getting a live wire temp in a set up that is being monitored during fully live operation would be a massive and expensive undertaking. Even if that was all overcome then we start bringing even more variables. Off the top of my head is "pull type". How much pull does the average user take in their drag? Then we have light drag, heavy drag, medium drag. Then we have the drag types on different air holes and location of air hole in relation to the coil....and on and on and on.

What I am going to do over the coming weeks is test the different coil materials and gauges. That will be easy, it just takes time and I have to get a lot of wire. Right now I only have .6 mm x .07mm flat Kanthal, 32g Kanthal and 28g Kanthal. I am going to order in all the round wire this week. Then I will order in all the flat the week after. Then I will do Nichrome. That will at least give us this data and we can go from there with different types of coil builds. Then we can do it wicked and with fluid. I really think, at the end of the day, this information will be useful for something. Such as testing different types of mods and different types of VV and VW theories for temp, efficiency, heat transfer through the coil, etc.

At the end of the day, defining the perfect vape is totally subjective anyway. However, putting science behind the build, we can at least come up with some idea of the heat transfer principles that are going on behind the scenes.

After I am done with all of this, I would love to compile a stockpile of all the common batteries available to us and run tests on those. It seems pretty obvious to me that a battery that heats up more uniformly is safer. Versus one that can create hotter spots. That logic might be flawed but it seems right.

 

[asdaq]

Hey jj , great stuff you are finding for the community, really. Can you see through plexiglass/acrylic? As long as the coil had a fair amount of distance from the inner wall, it is quite usable as a top cap:



Sent from my Nexus 4 using Tapatalk 4

 

[Mad Scientist]

That is a very good point to raise. Knowing the temperature is not helpful information by itself. It may be a way to see how different coil geometries affect temperature, but even that is just abstract data. It is the end results that must be compared to the various readings, and hopefully use that information to guide the e-cig designer towards a better end result.

I imagine the quantity of juice vaporized is one measurement that can be made. Other things that might be measured such as the vapor's particle size, or density, those are not easy to measure without specialized equipment. Air flow is another variable that is known to dramatically affect the quantity of juice vaporized.

It may not be too difficult to measure the weight of a drip atomizer before and after a test. But, the air flow is a more difficult item to settle on. What is a standard air flow? What is the starting temperature and humidity of the air?

An entirely different sort of thing would be the flavor, which might be affected by how it gets cooked by the temperature. There is no gauge to read that particular quality.

This measurement stuff is a lot more complicated than I initially thought. What is the most useful "low-hanging fruit"? I.e. what is easy to do, and will create a useful set of data?

-Joe Dunfee

A way to get started may be to take a baseline atomizer and build and plot time versus temperature using a standardized juice. Ideally also with a standardized airflow but multiple trials averaged would likely smooth out some of the subjectivity of the human factor of airflow (trying to keep it as simple as possible). This baseline data would then be compared to the data from a specific change from which to draw conclusions about the effect of a specific change.

I have a meter that can measure to the few nanovolts of output changes of a thermocouple as it changes temp but I don't have any thermocouple wire handy anymore. I haven't yet experimented with just kanthal or nichrome paired with plain copper (which will work), but likely will the next "rainy day" that comes along.

The thermocouple can be easily buried between the wick and wire with the thermocouple wires coming out the atomizer mouthpiece. If anyone has the right equipment, it seems like an interesting experiment. I just don't really have the time at the moment.

 

[jjkillian]

Hey jj , great stuff you are finding for the community, really. Can you see through plexiglass/acrylic? As long as the coil had a fair amount of distance from the inner wall, it is quite usable as a top cap:



Sent from my Nexus 4 using Tapatalk 4

It depends. My higher end systems all have adjustment for transmission. Mainly for IR windows. I would have to have a sample to know. It is pretty quick to figure out. Even then the close quarters of the target would cause issues potentially because the acrylic is still going to emit IR. So as it heats up I will pick up its signature. I would have to know the exact wave length at which the acrylic is close to 100% transmissive.

Here is an image of some light bulbs. The LED one is acrylic. Yet is still opaque to IR in the long wave spectrum.....as is the glass in the CFL and incandescent. While I can pick up the temp of the glass, I cannot see inside of it.



Here is a light bulb in short wave. The glass is 100% transmissive at this wave length, so I can see the filament.

 

[jjkillian]

So I found this pretty interesting based on yesterdays messing around.

Yesterday the coil was a dual .4 ohm 28g Kanthal wrapped at .81mm ID.

Today the coil is a dual .8 ohm 28g Kanthal wrapped at .5mm ID.



So here is my simple analysis of this. The temps are basically the same, but the surface area is longer in the .5mm ID coil and the temp is way more consistent across the coil. The larger and lower ohm coil had temp fall off towards the outer edges of the coil (edges closer to the legs).

So that brings up some questions. This coil was 2x higher the ohms, but much smaller in ID. IMO it performed way better. From what I have read, this actually goes against the consensus that lower ohm performs better. Yeah I saw a slight drop in temp on the higher ohm coil.....less than 3%.

Obviously there are too many differences going on between the coils to determine what is going on that is making it a more consistent temp pattern across the .5mm coil. I will have to build a .4 ohm dual .5mm or a .8 ohm .8mm one (this will be easier due to coil size).

I don't have time to pull the temp graphs at the moment, but will do it later. I remember yesterdays being very choppy across the coil with a big drop off near the leg edges, where this .5mm coil is very consistent across the coil with very little drop off near the legs. Temperature graphs look just like a wave form graph from an oscilloscope, except for temperature. The .5mm one looks very nice across the entire heating surface.

Lets keep the fact that the .5mm is basically not wickable in the middle out of the equation for now. I use it in the dragon coil set up.

 

[Alexander Mundy]

Testing with a draw brings in some new, and very hard to overcome challenges. First and foremost is I need line of site for the camera to work. IR doesn't "see through" anything. It picks up IR energy via the three forms of heat transfer (convection, radiation and/or conduction). The huge misconception with IR is that it can see through things, like walls. Yes I can see the studs and or missing insulation within a wall cavity, but that isn't what I am truly seeing. What I am actually seeing is the heat transfer from one side of the wall to the other and the Delta Ts associated with that. If someone had zero clue how a wall was built they would see nothing, because it isn't recognizable through familiarity of the structure. However, most of us know there are studs in the wall and because the studs transfer heat at a different rate than the other wall components to the surface (usually drywall) we can tell where the studs are.

Okay, so the point is, I need line of site. So then comes the obvious change in our application to get that line of site through the atomizer cap....just make one out of glass. Unfortunately, most of the IR equipment you see on the market cannot see through glass. Glass is opaque in the long wave of IR (7µm to 15µm approx). There are shortwave imagers around that at approx 3.5µm can see through glass. However I do not own one and they go for $50k+. There are plastics I can see through, but all would melt under the heat we are generating. That leaves us with some very specific and sometimes exotic materials they use in IR windows. None of which are affordable or easy to make, let alone made into an atomizer cap.

So that would then bring us back to heat transfer to the exterior of the caps we already have. Going back to my original train of thought......I could run tests on different wire materials then types. From that I can find the heat transfer to the cap and have a very educated guess of the coil temp. The main issue there is we are going to yield temp peaks and not "live" temps per say.

At the end of the day, getting a live wire temp in a set up that is being monitored during fully live operation would be a massive and expensive undertaking. Even if that was all overcome then we start bringing even more variables. Off the top of my head is "pull type". How much pull does the average user take in their drag? Then we have light drag, heavy drag, medium drag. Then we have the drag types on different air holes and location of air hole in relation to the coil....and on and on and on.

What I am going to do over the coming weeks is test the different coil materials and gauges. That will be easy, it just takes time and I have to get a lot of wire. Right now I only have .6 mm x .07mm flat Kanthal, 32g Kanthal and 28g Kanthal. I am going to order in all the round wire this week. Then I will order in all the flat the week after. Then I will do Nichrome. That will at least give us this data and we can go from there with different types of coil builds. Then we can do it wicked and with fluid. I really think, at the end of the day, this information will be useful for something. Such as testing different types of mods and different types of VV and VW theories for temp, efficiency, heat transfer through the coil, etc.

At the end of the day, defining the perfect vape is totally subjective anyway. However, putting science behind the build, we can at least come up with some idea of the heat transfer principles that are going on behind the scenes.

After I am done with all of this, I would love to compile a stockpile of all the common batteries available to us and run tests on those. It seems pretty obvious to me that a battery that heats up more uniformly is safer. Versus one that can create hotter spots. That logic might be flawed but it seems right.

I could send you some Rene41 if you wish.
Also have some 1mm X .05mm Kanthal which is an odd duck.

 

[dr g]

A huge factor that has been passed over in this thread is Time.

No it hasn't, or at least not by some of us.

Now in regards to flavor, I feel that the burnt taste that you get is a result more of the PG rapidly evaporating and leaving behind the flavor particles which will then burn as the coil heats up due to reduced liquid. This also causes the wick to burn (well at least in my case, i use cotton). This is a direct result of the watts-per-surface area. Thinner awg has a higher watts/surface area than the thicker awg.

Try vaping (very small taste!) a dry coil before you wick it ...

Correct me if I'm wrong but there seems to be a distinction between what our vapor is vs the actual boiling point of PG. Our vapor is very tiny drops of liquid, whereas if you were to rappedly boil flavored ejuice the PG would dissipate as steam leaving behind the flavor particles.

This is the basic nature of atomization, it requires rapid boiling but the boiling action creates a very fine mist.

 

[cadcoke5]

Our vapor is very tiny drops of liquid, whereas if you were to rappedly boil flavored ejuice the PG would dissipate as steam leaving behind the flavor particles.
...
A start would be to run the test using the same atomizer, with a very specific air intake hole, and by using just straight 0mg PG, then varying the juice to say 6mg 80/20 PGVD no flavoring.

I love the theoretical discussion that is happening here.

Obviously some of the flavor makes it into the atomized liquid, or we would not taste anything. Since H20 as a gas is about 1,000 times the volume in liquid form, I think the process of atomizing the liquid carries away with it both non-gaseous liquid and the flavor particles, sort of like an explosion carries debris. So, some of the liquid is atomized by the explosion itself, while some of it is the actual gaseous vapor that eventually condenses back into liquid droplets. There is also evidence that the vaporization process tends to leave behind something with a lower evaporation temperature, as evidenced by the syrupy liquid left in my atomizer after atomizing several tanks full.

My conclusion from the above, is that the quantity of liquid lost from the coil is not something that can be predicted by using the wattage, the heat of vaporization, and the final temperature of the vapor.

On a slightly different subject, I will ask jjkillian; Can you see the temperature of the vapor cloud with your camera?

Regarding airflow and the problem of how to control it.

jjkillian said;
Testing with a draw brings in some new, and very hard to overcome challenges. First and foremost is I need line of site for the camera to work. IR doesn't "see through" anything

I suspect an IR transparent enclosure is going to be a problem because the vapor will tend to accumulate on the surface.

For my fire breathing dragon puppet design, I use a fish-tank air pump to blow through the atomizer. I found some vinyl tubing that would fit around the outside perimeter of the atomizer an a reducer fitting to go to the air hose. Finally, there was a separately wired electrical connector to the atomizer that I had to bring through the vinyl tubing.

However, for the testing you might do, it might be better to define a "standard draw" and a simple mechanism to produce it. The fish tank aerator is not a good choice because of the tiny pulses from the pump. Rather, I would suggest a very old design for producing predictable air flow. It is a pipe organ air accumulator. Basically, it is a billows with a weight on top. Air would flow in from the air pump, and then inflate the accumulator if the outflow were greater than the inflow. The weight on top would keep the pressure even.

A fireplace billow may be a good substitute for the organ air accumulator, and might work with little or no modification, but the hinged mechanism makes calculations more difficult. So, for a standardized "draw" mechanism, I am proposing another variation shown in the drawing below. It is a portion of dryer vent hose. It is glued to a wood base that has some air holes in the bottom. One for air-in, with a flap on top. And the 2nd is for an air outlet. The 4 posts keep the billows from flopping to the side, while a weight on top provides the pressure. Some tubing from the air outlet exiting below is how the air flow is directed to the atomizer.


Proposed Standard Draw Mechanism.

My concerns with this design, is that the weight on billows may be prone to tipping to the side, despite my posts on the side. Also, the vinyl vent hose may have enough stiffness to it, to add its own resistance to being compressed. It might be best to have a stop at the bottom of travel so that it does not go all the way down, where the compression of the vinyl gets worse.

The measurement of a standard draw may be done by connecting this apparatus to an atomizer like it would be done for testing the atomizer, but omit the weight on the billows and add the standard atomizer cover. Then, have an individual take a draw, noting how far the billows moves and the duration. Then, add weight until you can reproduce the same volume and speed of the persons draw.

-Joe Dunfee

 

[Alexander Mundy]

For air draw, how about water?
If you wish to create a negative air flow a graduated cylinder with a lid that has an air hose attachment and a water outlet that can have various restrictions for flow.
For positive, 2 cylinders side beside with the water flowing into the one with the lid.
Don't know if those would work, just throwing it out there.