The Pyrex SS hybrid Wick

[dsy5]

Per the 4th page in the mouser.com provided PDF on Panasonic Prolytic Graphite Sheets, page 4, the thermal conductivity (Watts/Meter-Kelvin) for PGS 100μm is from 600 to 800 in the X, Y directions. In the Z direction, 15.
http://www.mouser.com/pdfdocs/ThermalGraphiteSheets.pdf

Units of heat applied to the surface of a 1 cm square area of PGS 100μm will travel an average of 0.5 cm to reach the 1 cm edge of the area. The same energy will travel 0.01 cm to pass through the surface of the 100 micrometer sheet.

I'll give some bias to the X, Y directions and choose a value of 750 W/m-K.

10 Watts applied to surface and traveling in the X, Y directions will generate 10 Watts/0.005 meters = 2,000 units.

10 Watts applied to the surface and traveling in the Z direction will generate 10 watts/0.0001 meters = 100,000 units.

Now for the offered thermal coeficients...750 for X,Y and 15 for Z...
2,000 units x 750 = 1,500,000. 100,000 units x 15 = 1,500,000.

For the size of 1 cm x 1 cm and 100μm thickness, the energy traveling in the Z-axis is the same as the energy traveling in the X and Y axes.

This is proof enough for me that the Z axis contains significant thermal conductivity relative to the area of material as might be utilized in an SS Mesh wrapped wick. Further adding to the energy which might pass through the Z axis is the notion that the prolytic graphite sheet of 1 cm x 1 cm AND rolled into a tube would elimante the heat flowing out in the X and Y axes. That limit of the flow away from the mesh would create more heat than if we were dealing with an unbounded 1 cm x 1 cm area within a continuous sheet as would be implied by the calculations.

If thermal transmission capacity is the only criteria, I suspect the Graphite Sheets will work fine. Number of possible layer and such are beyond this illustration. While the thermal capabilities seem encouraging, there may be physical properties and possible electrical conductance concerns that remain to be understood more clearly. As well, the Graphite Sheets have a specified Heat Resistance value of 400 degrees C.


F.A.U.F. (Factual And Useful Formulas)
1 meter = 100 cm = 1,000 mm = 1,000,000 μm
1 inch = 2.56 cm
1 cm = 10 mm = ~0.3937" = ~3/8".
The circumfrence of a 3/32" diameter wick is about 0.748 cm or 7.48 mm


This poster reserves the right to edit the post as he sees fit.

I appreciate seeing your calcs, they appear well thought out and to be correct. Only problem with the stuff now is that it is more conductive, apparently, than stainless steel. And we've just seen a coil (not thouroughly tested, of course) reach around 550ºC. I'd have to conclude that this is not the answer we're looking for. You could paint it and roll it in ceramic and all other kinds of good things, but then that is really complicating things.

Maybe when Bapgood gets his order in, he can confirm/disprove the conductivity and temperature resisting issues.

 

[MattB101]

Cool,
Thanks very much. Most went right over my head but, I got some of it anyway.

I can't back it up with data but I am hoping it isn't conductive. Probably wishing in vain, that would be too easy.

Goodnight all. See you in a.m. unless insomnia strike again.

Sent while sitting on my .... in my living room vaping away!

 

[mre777]

A coil may be able to reach those temperatures but how often do we do that? I don't like fried juice. I don't have any heat testing equipment, If anyone reading does have some I would like to see a series of tests on normal coil usage temps up to and including chain-vaping (because thats me) That would be something to work around.

 

[Cool_Breeze]

well said....now i get it thanks!

oops wrong quote the first time

Yes, it's power/distance. The Z-distance is very small.

 

[dsy5]

A coil may be able to reach those temperatures but how often do we do that? I don't like fried juice. I don't have any heat testing equipment, If anyone reading does have some I would like to see a series of tests on normal coil usage temps up to and including chain-vaping (because thats me) That would be something to work around.

I agree with that, I don't think that normal operation would be a problen in the area of its temperature tolerance. But there are some devices you can't turn off and it it accidently gets stuck on...

And then there is the issue of conductivity - hope the specs are misrepresented, but it does say 10000 Siemens/cm.

 

[bapgood]

The PGS I orded was the 25um it was the thinnest (0.025mm hopping that helps rolling) and the best heat transfer that was available and had a higher siemens of 20000 S/cm

 

[Cool_Breeze]

...but how often do we do that? ...

It seems to me the reason for SS Mesh is to be able to dry burn the wick. The frequency of that depends upon the make up of the juice and the heat created as well as the frequency of vaping. The reason for cladding the wick is to electrically insulate the SS Mesh which we use for longevity via dry burning.

The answer to your question is, 'Only once,' if it wrecks your wrap.

 

[mre777]

I agree with that, I don't think that normal operation would be a problen in the area of its temperature tolerance. But there are some devices you can't turn off and it it accidently gets stuck on...

And then there is the issue of conductivity - hope the specs are misrepresented, but it does say 10000 Siemens/cm.

Nah im going with very conductive on that one lol. Not often is something that thermally conductive and not electrically conductive. Plus its carbon. And as a law Siemens is inversely proportional to ohms. G(measured in siemens )=1/R(ohms)

 

[dsy5]

Nah im going with very conductive on that one lol. Not often is something that thermally conductive and not electrically conductive. Plus its carbon. And as a law Siemens is inversely proportional to ohms. G(measured in siemens )=1/R(ohms)

And Bapgood got the stuff thats twice as high... (hope we're wrong Bapgood)

 

[jubal81]

A coil may be able to reach those temperatures but how often do we do that? I don't like fried juice. I don't have any heat testing equipment, If anyone reading does have some I would like to see a series of tests on normal coil usage temps up to and including chain-vaping (because thats me) That would be something to work around.

This would be some excellent data to have. Temperature is really what we're going for, but devices are metered in volts and amps. A temperature sensor or a lot of data to write a good table for the microcontroller software operating the buck-boost circuit would be a revelation.

 

[bapgood]

It seems like I will likely eat my words about the PGS not being electrically conductive

 

[dsy5]

It seems like I will likely eat my words about the PGS not being electrically conductive

But we still love ya for taking one for the cause...

 

[bapgood]

And Bapgood got the stuff thats twice as high... (hope we're wrong Bapgood)

But twice as high is good....better than stainless at least I have stainless at 14500 s/cm

on that subject (yes i should just go test) is the coil grounding on dry stainless or because of the juice....either way it won't likely make a difference to the PGS

 

[mre777]

You never know when something like that will be really useful, and you will have it on hand to use for testing instead of waiting for it in the mail
It would likely make awesome contacts on coil wrapping posts.

 

[Cool_Breeze]

I'm informationed-out right now, but maybe there is something here if someone can give it a little study.

http://www.ceramicindustry.com/ext/resources/files/CCD-MP-Charts-4.pdf

 

[Scubabatdan]

OK. Here's an enamelled coil...

Here it is threaded onto an unoxidised wick...

And here is the initial firing with no shorting...

I heated the coil and dipped it into the enamel powder about ten times to achieve this coating.

I did some looking around and research on enamel powder, seems it is an enamel colored glass that can withstand temps of 450c. Hmmmm I wonder if the coil were tighter if the enamel would bridge between the coils, and I have found curing temps need to be in the 550c range since it is fused glass capable of withstanding 450c temps and from what I have found non toxic once fired. I might have to take the plunge and get some quality enamel powder to test. Definatly would do about 3-4 coats or dips in the powder and electrically heat the coil to set the enamel.
Cool somthing new to play with.
So far I have gone through 5 tanks of juice on my DUD and she is working great. I have not gotten the volume of vapor that a low ohm coil can produce but at 2.8 ohms and 11.5 watts I am pretty pleased with it.
Dan

 

[mekks082]

Man, right now there are so many DUDs, CHUDs, ChIDs, DIDs out there, I'd say you may want to be a bit more specific. Any idea what the approx size of the wick port is on yours right now? May be kind of a moot point right now as you're probably vaping it as you type...

MOV Genesis Style Rebuildable Atomizer Tank

That is the version I have.

 

[gdeal]

Ok.. I’m back. Things got a bit busy this evening. I put together a new setup with the AGA and 3mm thin wall pyrex tube. I cut a 15mm piece, wrapped a 1.5 ohm 6 turn 28g coil Petar K style. Gently worked the tube in, then slide in the wick, fired away, low v’s at first and worked my way up to ~4.2v. From initial set up to first fire, took about 25 minutes in total, 10 minutes spent on the diamond wheel smoothing tubing edges.

Vapor production – Check.
Vap quality – good, not great (yet).

Same issue as before with the fuse version. Airflow. I was able to get the wick lower to ~5mm off the base, just at the height of the air cap inlet. I put an extra oring on and got another 1mm or so. So the air inlet is now almost 2mm above the tip of the tube. The vape is still a bit airy, compared to say a dud. So this may just be how the AGA vapes, but as I raised that airflow hole, vape improved significantly. I have the airhole directly aligned with the wick and found it worked best there. I may drill the cap tomorrow about 3 or 4mm higher than stock.

On test fires, I got the coils to glow a couple of times. No issues from a glass perspective. It didn’t explode or crack. I did take the temps up gradually, so to minimize thermal shock. We will have to see how it handles repetitive stresses.

There are a couple of interesting effects going on compared to the 5mm fuse tube version. This setup heats more quickly at the same amps, but can’t handle higher watts (~11 watts vs 14.5 watts for the 5mm tube). The 5mm which is thicker walled glass obviously will take more time to heat, but once it got up to speed, it felt like I had a more even vaporization of juice. The larger mass of the wick in the coil/tube seemed to handle the thermal build up a bit better.

Looking forward to hearing results from others.

A couple of pics.


Compared the 5mm Fuse tube:

 

[mre777]

what do you mean it can't handle higher watts whats it doing? Setup looks really good!

 

[jubal81]

Great report, gdeal.

I found some 2mil Kapton tape that's rated to 260C. THey say they have reports of it taking up to 400C.