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can someone smart explain a couple things about heating air?

vaporonly

living in a van down by the river
hi.

so i've been trying to track down more info on this.

so a wand vape like the SSV has a pretty short path for the air to heat up next to the ceramic rod.

a vape like the supreme advertises a long path for the air to heat up in the different "levels" of the heat block.

how important is this length of the path for the air to heat up?

Is there any formula or relationship between how long the path is and how warm the air is heated??

thanks
 
vaporonly,

Hippie Dickie

The Herbal Cube
Manufacturer
i have some empirical results, rather than by formula ... my heater is 1.5" long, the volume of air passing by the heater is a cylinder 14mm diameter by 1mm thick by this 1.5" long.

A long slow inhale, say 15 seconds (or longer), will bring the temperature of the herb to setpoint temperature (typically 380°F) with no problem throughout the inhale.

if that makes any sense.
 
Hippie Dickie,

Egzoset

Banned
Salutations,

If you could have formulated your question so that normal members not part of the elite might consider participating then maybe i'd have been tempted to highlight the fact that a Silver Surfer heat-exchanger and that of a Supreme hardly seem appropriate for a comparison: surface was optimized in the second example only, for example. Euh... But only a smart guy will know for sure...

:peace:
 
Egzoset,

OO

Technical Skeptical
I'm not smart, BUT...

To answer the question, it's not how long the air path is, it's how much contact there is between the air you're trying to heat and the surface of the exchanger. Factors that affect this are the surface area of the exchanger, and length of time the exchanger is in contact with the air (which is further influenced by velocity of air over the surface (draw speed), as well as the length of the heat exchanger).

Other factors to consider are the thermal conductivity of the heat exchanger, as well as fluid dynamics, of which I don't know enough about to speak with any confidence on.

I'm sure there that a formula can be written to describe the relationships, but again, that's a bit further than I'm able to speak confidently about.

I do plan on learning these things eventually, but if you're interested in them, why not study these subjects? They're all very interesting.

As for the supreme, the supreme's exchanger is made of aluminum, which conducts heat exceptionally well, and as a result, heating only one portion of it is unlikely to cause regions of uneven temperature.
Temperature is (unfortunately the wikipedia definition really needs some cleanup) an average of kinetic energy in molecules. I would read this part, and any related articles until the general idea is understood.

Each variable should be considered independently, though heat energy affects temperature.

Essentially the temperature is not what causes volitization of molecules, it is enough energy(often in the form of heat) to cause the molecule to no longer feel physical/chemical attraction to the surrounding molecules, and the molecule gets promoted into the gaseous state.

So there's a large number of factors to consider to get a good understanding of the process.

That being said, if you want evidence about how unlikely you are to cause significant regions of different temperature on the supreme, you can ask an experienced welder to show you how to weld aluminum with a flame.
 

vaporonly

living in a van down by the river
Salutations,

If you could have formulated your question so that normal members not part of the elite might consider participating then maybe i'd have been tempted to highlight the fact that a Silver Surfer heat-exchanger and that of a Supreme hardly seem appropriate for a comparison: surface was optimized in the second example only, for example. Euh... But only a smart guy will know for sure...

:peace:

that smart thing was tongue in cheek. anyone is encouraged to post.

the objective of the SSV heater and the Supreme heater is the same, to heat the air.

i'm just attempting to understand the relationship of say heating the air in 4 inches of heater path vs say 20 inches of heater path
 
vaporonly,

vaporonly

living in a van down by the river
i have some empirical results, rather than by formula ... my heater is 1.5" long, the volume of air passing by the heater is a cylinder 14mm diameter by 1mm thick by this 1.5" long.

A long slow inhale, say 15 seconds (or longer), will bring the temperature of the herb to setpoint temperature (typically 380°F) with no problem throughout the inhale.

if that makes any sense.

thank you for the empirical data. did you ever try a different length heaters?
 
vaporonly,

Stu

Maconheiro
Staff member
that smart thing was tongue in cheek. anyone is encouraged to post.

the objective of the SSV heater and the Supreme heater is the same, to heat the air.

i'm just attempting to understand the relationship of say heating the air in 4 inches of heater path vs say 20 inches of heater path
One difference that should be considered when comparing the SSV to the Supreme is that the SSV has a ceramic heating element that is constantly heating (thereby actively heating the air that passes by it). However in the case of the SV, the heating element during use is designed to heat the air passing through the maze, but the heat is constantly losing energy as it is cooled by the air passing through it (assuming the flame has been removed from the equation during the hit).

So in one case, we have a "always on" ceramic heating element (SSV) while on the other hand the SV's (pre-heated by flame) heat exchanger is in a state of cooling once the torch has been removed. The long airpath of the SV helps minimize the cooling effects of the air passing through it.

:peace:
 
Stu,
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Hippie Dickie

The Herbal Cube
Manufacturer
thank you for the empirical data. did you ever try a different length heaters?

Yes. i had one design where the glass heater tube was 6" long - kind of like the bamboo in The Cloud. This model got too friggin' hot on the outside shell so i ditched the design.

i find 1.5" is sufficient for my vape.
 
Hippie Dickie,

vaporonly

living in a van down by the river
I have been doing some more reading and I think I may have stumbled onto something I am looking for:

for an unfinned tubular heat exchanger, neglecting fouling terms, the overall heat transfer coefficient, U, is buried in this equation....

1/(U * A) = 1/(Hi *Ai) + ln(Do/Di) / (2*pi*k*L) + 1/(Ho * Ao)

where
subscript i relates to inner diameter or area.
subscript o relates to outer diameter or area.
L is total tube length
k is material conductivity
pi = 3.1415......
H is convection coefficient from inner or outer surfaces
D is tube diameter
A is *surface* area = pi * D * L

then calculate the heat transferred by

Q = U * A * LMDT

where LMDT = log mean temperature difference.

http://www.eng-tips.com/viewthread.cfm?qid=94474

in that post he was looking for U. I'm interested in the L, as well as subscript i and o
I'll keep digging around...

thanks for everyone's input.
 
vaporonly,
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max

Out to lunch
One difference that should be considered when comparing the SSV to the Supreme is that the SSV has a ceramic heating element that is constantly heating (thereby actively heating the air that passes by it). However in the case of the SV, the heating element during use is designed to heat the air passing through the maze, but the heat is constantly losing energy as it is cooled by the air passing through it (assuming the flame has been removed from the equation during the hit).

So in one case, we have a "always on" ceramic heating element (SSV) while on the other hand the SV's (pre-heated by flame) heat exchanger is in a state of cooling once the torch has been removed. The long airpath of the SV helps minimize the cooling effects of the air passing through it.

:peace:
The last sentence is the key to the difference. The long air path and large surface area of the Supreme's heater serve to do a better job of heating all the air, as well as retaining the heat so you don't have to break out the torch again so soon. I've used both models. The heater designs are very different but both are well suited to the overall vape design each manufacturer chose.
 

Frederick McGuire

Aggressively Loungey
How important the length of the path is would relate to how hot the path is I would think...

With the SSV vs Supreme comparison, I'm fairly sure the SSV ceramic rod gets far hotter than the Supreme's Aluminium Heater block.

The room temp air quickly passing by the very hot element of the SSV picks up a small amount of the total heat available, but enough heat for our uses.
The room temp air taking a longer time to pass through the longer but cooler Supreme path picks up more of the total heat available (but the same amount of heat overall [assuming we are talking about the same volume of air being heated to the same temp]), but still gets to the same (or similar) temp as above.
So hotter and shorter path can give similar results to cooler and longer path.

So long as the air is at the right temp at the outlet of the vape, I don't see how long the path is as a relevant factor to vaping.
Though I guess it would be something useful to consider if you were designing your own vape.

That's just my take on it :2c:
 
Frederick McGuire,
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OO

Technical Skeptical
The last sentence is the key to the difference. The long air path and large surface area of the Supreme's heater serve to do a better job of heating all the air, as well as retaining the heat so you don't have to break out the torch again so soon. I've used both models. The heater designs are very different but both are well suited to the overall vape design each manufacturer chose.
Not quite.

The reason the SV doesn't loose it's heat too quickly is the same reason that it takes so long to get it to working temp. The reason is that it has a relatively low external surface area.

That said, if air is continually drawn through the SV, the temperature will very quickly drop.

The high INTERNAL surface area of the supreme is the cause of this. This aspect as well as the fact that aluminum has high thermal conductivity and low mass make this heat exchanger quite advanced in the world of vapes. This is because the air that comes out is quite uniformly heated. Whether it is over-engineered or not depends on what you want.
How important the length of the path is would relate to how hot the path is I would think...
Yes, but other factors matter like surface area and thermal conductivity, as well as velocity of the air.
With the SSV vs Supreme comparison, I'm fairly sure the SSV ceramic rod gets far hotter than the Supreme's Aluminium Heater block.

The room temp air quickly passing by the very hot element of the SSV picks up a small amount of the total heat available, but enough heat for our uses.
The room temp air taking a longer time to pass through the longer but cooler Supreme path picks up more of the total heat available (but the same amount of heat overall [assuming we are talking about the same volume of air being heated to the same temp]), but still gets to the same (or similar) temp as above.
So hotter and shorter path can give similar results to cooler and longer path.

So long as the air is at the right temp at the outlet of the vape, I don't see how long the path is as a relevant factor to vaping.
Though I guess it would be something useful to consider if you were designing your own vape.

That's just my take on it
The difference comes from the uniformity to how the air is heated (the kinetic energy is not evenly distributed amongst air molecules), which can affect scorching, but that would mean delving into the field of fluid dynamics, something I want avoid for the meantime. But most of your post reflects a proper understanding of the differences.
 
OO,

vaporonly

living in a van down by the river
The high INTERNAL surface area of the supreme is the cause of this. This aspect as well as the fact that aluminum has high thermal conductivity and low mass make this heat exchanger quite advanced in the world of vapes. This is because the air that comes out is quite uniformly heated. Whether it is over-engineered or not depends on what you want.

I'm always impressed how uniformly spent the material is, without any stirring or shaking. I know this also has to do with bowl shape too but I can't help but think that the air being heated uniformly like you said in turn evenly vapes the material.
 
vaporonly,

Hippie Dickie

The Herbal Cube
Manufacturer
@vaporonly
unfinned tubular heat exchanger

how is this tubular heat exchanger configured to operate -- i.e. does the ambient air go through the interior of the tube, or across the exterior surface.
 
Hippie Dickie,

OO

Technical Skeptical
I'm always impressed how uniformly spent the material is, without any stirring or shaking. I know this also has to do with bowl shape too but I can't help but think that the air being heated uniformly like you said in turn evenly vapes the material.
Most vapes I use share the same shape, so I think it may be less of a factor.
@vaporonly


how is this tubular heat exchanger configured to operate -- i.e. does the ambient air go through the interior of the tube, or across the exterior surface.

I think it's meant to go either way. I suspect ambient air is meant to move across the exterior as is the case with most industry heat exchangers.
 
OO,

Hippie Dickie

The Herbal Cube
Manufacturer
so, Di and Do define the tube of air that hugs the exterior of the heat exchanger tube ... maybe constrained by an external shield (to set the Do value, i.e. the height of the air above the exchanger surface)
 
Hippie Dickie,
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