Compact VM head, coil in a box

Vapor, Liquid or Cooling Management. Flutes, plates, etc.

Moderator: Site Moderator

punkin
Master of Distillation
Posts: 2711
Joined: Fri Oct 05, 2007 12:36 pm
Location: Northern NSW Oz Trail Ya

Re: Compact VM head, coil in a box

Post by punkin »

HookLine wrote:Manu, can you please reduce the data size of those photos. They chew up nearly 2 MB of bandwidth every time we reload the page, and also chew up storage and bandwidth for Uncle Jesse. You should be able to get them down to about 70K each, without losing any clarity or detail.

Thanks
Hook

Not if he's on your ignore list they don't :wink:
snuffy
Swill Maker
Posts: 296
Joined: Sat Sep 13, 2008 8:21 pm

Re: Compact VM head, coil in a box

Post by snuffy »

If somebody would like to take a crack at explaining the hydrodynamics of "stream splitting" I'd be grateful. I've seen the phrase used several times and I don't understand how it varies from the explanation I've worked out. If there is a stream splitting effect, it would appear to be dependent on the density of the fluid in the column.

entia non sunt multiplicanda praeter necessitatem
Time's a wasting!!!
DestructoMutt
Swill Maker
Posts: 321
Joined: Thu Jun 14, 2007 4:41 pm
Location: Not that Vancouver, the original one.

Re: Compact VM head, coil in a box

Post by DestructoMutt »

destructomutt wrote-
the auto-shutoff isn't so much a shut-off as a "gap" in production. most operators reduce the heat supplied to the boiler once boiling commences. this reduced heat is sufficient to produce vapor when the boiler contains ethanol, water and the other by products of fermentation. so, between 64deg C and 98deg C, there is a semi-constant production of vapors from the boiler, but between 98deg C and 100deg C, there is a noticeable lag in vapor production. if however, one were to increase the heat to the boiler when the temperature of the column were to reach 96deg C, the gap in vapor production would diminish. it's this lag or gap in vapor production that we see as an auto-shutoff effect.
if a majority of the material that boils below 98degC is eliminated from the system, and the remaining components boil at 100degC or over, there will be a period of decreased vapor production. and you're correct, the production does fall gradually as 98degC is reached.

keep in mind though that water needs more energy to vaporize than ethanol does, and if you supply the energy slowly, the time of the gap from 98degC to 100degC will appear longer than if you supply the energy more quickly.
i need to modify these paragraphs and didn't know how to do it, without it appearing deceitful.

regarding the auto shut-off phenomonon; vapor is produced at 45 liters a minute per kilowatt of energy input. vapor production is not reduced. with a majority of the material that boils below 98degC eliminated from the system, and a majority of the remaining components boiling at 100degC or over, they won't be able to reach the top of the column due to the reflux condensor keeping the top of the column below 100deg C. with a reduction in volume of vapor reaching the top of the column there is even less being sent to the product condensor. [vapor management splits the vapor stream into two paths, with a majority going to the reflux condensor and a small portion going to the product condensor.] the result is that there is an apparent shut-off in product production.
HookLine
retired
Posts: 5628
Joined: Sun May 13, 2007 8:38 am
Location: OzLand

Re: Compact VM head, coil in a box

Post by HookLine »

Thanks, Manu.
Be safe.
Be discreet.
And have fun.
DestructoMutt
Swill Maker
Posts: 321
Joined: Thu Jun 14, 2007 4:41 pm
Location: Not that Vancouver, the original one.

Re: Compact VM head, coil in a box

Post by DestructoMutt »

snuffy wrote-
VM is a dynamic process based on water and alcohol vapors having lower and higher densities than air. Density of gas or vapor makes a big difference on how they flow in a open vertical column.

Pure water vapor is lighter than air. Not only does it rise in the column, it "floats" up and reduces the pressure inside the column relative to the atmosphere. This will prevent it from flowing out the side arm and descending the product condenser.

Pure alcohol vapor is heavier than air. It is "pushed" up the column by the pressure of the vapor below it. As it rises up the column, the pressure in the column increases above atmospheric.
vapor is produced at 45 liters a minute per kilowatt of energy input, no matter what the composition of the wash is. this vapor is expanding to fill it's container and it is constantly being produced as long as the energy is being supplied. this action is what pushes the vapor up the column. also, the vapor produced is a homogenous mixture. the high volatile components climb the column due their low boiling point. they remain vapor longer than the low boiling point components, and continue on their journey up the column. vaporization - condensation - repeat. vapors climb, condensates sink.
A mixture of water and alcohol vapor will vary in density depending on the %abv of alcohol. At 41%abv, the density of the water/alcohol vapor is the same as air. This is the cutoff point where VM heads stop producing. By coincidence, it is also the cutoff point where US distillers have to stop collecting product. I take this as a sign (like the existence of beer) that God loves us.
VM heads stop producing because low boiling point products are removed from the system, almost completely.
When the %abv of the vapor is greater than 41%, the vapor will flow down the product condenser. The farther the fall before the vapor hits the condenser, the greater the pressure differential between the top and bottom of the vertical leg of the product discharge tube.
see above regarding vapor production.
Once the vapor is cooled, the volume it occupied is replaced by air that initially filled the discharge tube and was pushed down by the water/alcohol vapor as it initially entered the tube.
this appears to imply a vacuum - condensate will revaporize and fill the vacuum with vapor faster than outside air can be sucked in. the condensate is in the area, it is close to boiling, having just been cooled to just below boiling, and the vacuum (if actually existing) drops the boiling point of the condensate, hence flash revaporization.
This downward flow is a fluid siphon and the hydrodynamics of siphons apply. There is a nice demonstration experiment showing how carbon dioxide (which is heavier than air) can be siphoned just like water.

Because the top of the column and the bottom of the product discharge tube are open to the atmosphere, the column is almost at ambient pressure. The very slight pressure differential is solely due to the difference in density between the vapor and air.
see above regarding vapor production. 45 liters a minute per kilowatt of energy input. a siphon implies vacuum - see above regarding vacuums and revaporization to fill the vacuum.
As long as the fluid coming out of the boiler is above 41%abv (which is the same as saying that it is denser than air), it will flow like a liquid up the column and out the valve opening.
how do you account for the production of ethanol from a wash that is lower than 10%ABV? or should i ask how do you account for the vapor from a wash that is less than 10%ABV filling a column and producing product? as in a refractionating column (no reflux condensor) or even a pot still?
snuffy
Swill Maker
Posts: 296
Joined: Sat Sep 13, 2008 8:21 pm

Re: Compact VM head, coil in a box

Post by snuffy »

This talk of hypothetical but non-existent vacuums in systems open to the atmosphere is misleading and decidedly Aristotelian. There are positive and negative pressure differentials.

If a vacuum is necessary, would a mercury siphon work on the moon?

Here is a lovely demonstration of the classical "chain siphon" experiment: http://jedlik.phy.bme.hu/~hartlein/phys ... /f4-32.htm" onclick="window.open(this.href);return false;" rel="nofollow

It is unnecessary to invoke a conceptual vacuum to explain the operation of a siphon. A trip to Occam's barber shop is in order.

I agree that the vapor being produced in the boiler displaces the atmosphere. However, this displacement does not, ipso facto, produce a positive pressure inside the column. The density of the vapor is crucial. If the vapor is lighter than air, there will be a negative pressure where the column connects to the outside atmosphere.

At 45 liters/KWmin, the result is a vapor speed in an unpacked column of about 20 inches/sec for the typical heat input. The vapor velocity reduces the pressure due to Bernulli's law. But not by much and the pressure differential is constant at constant velocity/heat input. Density is the controlling factor.

Thought experiment: a refluxing column has a LM head mounted directly over the VM head. Both takeoff heads have their valves adjusted to a tiny trickle, so as to minimize the interaction. If VM works as I described above, when the VM cutoff point approaches, the VM head will cease producing as the density of the vapor falls and the LM head will continue. The boiler runs with constant heat input throughout and its rate of vapor production has no effect on the observed results.

It's a simple experiment and one that would settle the controversy definitively.
Time's a wasting!!!
rad14701
retired
Posts: 20865
Joined: Wed Dec 19, 2007 4:46 pm
Location: New York, USA

Re: Compact VM head, coil in a box

Post by rad14701 »

A glass or acrylic VM column would help tell that tale... Yet another piece of the puzzle that I'd like to determine is how much effect the reflux condenser has on the process... It seems that if the condenser is too efficient then it would push the boundary layer down below the take-off, thus causing take-off to cease... Vapor rising and colder air pushing it back down... That's more or less how the process works in layman's terms, aside from the normal concept of having the vapor condense on the condenser and drop as liquid... If you push the boundary layer down to the top of the packing then you won't have that happening... No reflux and not take-off... Not that it would work like that, but just some theoretical interjection tossed in to chew on...
DestructoMutt
Swill Maker
Posts: 321
Joined: Thu Jun 14, 2007 4:41 pm
Location: Not that Vancouver, the original one.

Re: Compact VM head, coil in a box

Post by DestructoMutt »

snuffy wrote -
This talk of hypothetical but non-existent vacuums in systems open to the atmosphere is misleading and decidedly Aristotelian. There are positive and negative pressure differentials.
i'm sorry if i implied that a vacuum exist in a compound refractionating column. i was merely trying to show/explain that if a vacuum existed it would be eliminated through revaporization of condensate.
I agree that the vapor being produced in the boiler displaces the atmosphere. However, this displacement does not, ipso facto, produce a positive pressure inside the column. The density of the vapor is crucial. If the vapor is lighter than air, there will be a negative pressure where the column connects to the outside atmosphere.
the vapor is constantly being produced and expanding away from the boiler, condensate returns to the boiler, not vapor. what do you call the force exerted by one substance against another when the substances are vapors/gases? i've been taught that this is called pressure.

think of this: under standard conditions you are given a container with an open top, a closed bottom and an inlet at the bottom. attach a hose to the inlet and fill the container with helium. it won't work because the helium being lighter than air, pushes past the air in the container and out the open top. retry by turning the container over, it works because the helium is trapped by the now closed top of the container and the air is pushed out the now open bottom. if, in the first part of this experiment, carbon dioxide had been used, then the CO2 being heavier than air would have pushed the air out the open top of the container.
Thought experiment: a refluxing column has a LM head mounted directly over the VM head. Both takeoff heads have their valves adjusted to a tiny trickle, so as to minimize the interaction. If VM works as I described above, when the VM cutoff point approaches, the VM head will cease producing as the density of the vapor falls and the LM head will continue. The boiler runs with constant heat input throughout and its rate of vapor production has no effect on the observed results.
if the vapor management head is properly working, there will not be any vapor getting by its reflux condensor to reach the liquid management head.

rad14701 wrote -
It seems that if the condenser is too efficient then it would push the boundary layer down below the take-off, thus causing take-off to cease... Vapor rising and colder air pushing it back down... That's more or less how the process works in layman's terms, aside from the normal concept of having the vapor condense on the condenser and drop as liquid
nixon and mccaw discuss this in detial in their book, "the compleat distiller". basically it's a self canceling/regulating process, if there is no vapor reaching the reflux condensor there is no condensate to drip back and cool the top of the column. heat flows to cold. cold does not radiate away from the condensor. one of the basic laws of thermodynamics.

it's not colder air that is pushing down, the molecules in the vapor have absorbed heat and have phase jumped from liquid to vapor, the molecules in the vapor are carrying the heat, the molecules in the vapor release the heat energy to the reflux condensor when they run into it. when the heat/additional energy that allowed them to phase jump is gone, they revert back to liquid form.

edit for spelling and grammar
snuffy
Swill Maker
Posts: 296
Joined: Sat Sep 13, 2008 8:21 pm

Re: Compact VM head, coil in a box

Post by snuffy »

I wish your helium example would work for distilling. All the steam (lighter than air) would rush out the top of the column and only the alcohol (heavier than air) would be left behind. :wink:

Here's the layout for the thought experiment. Both LM and VM heads on the same column. It might actually be worth doing, since you could switch to LM when the VM slowed down too much.
dualhead.gif
dualhead.gif (4.63 KiB) Viewed 1565 times
Of course, you could put the VM on top and the LM below it if you thought that would make a difference. I don't see that it would.
Time's a wasting!!!
DestructoMutt
Swill Maker
Posts: 321
Joined: Thu Jun 14, 2007 4:41 pm
Location: Not that Vancouver, the original one.

Re: Compact VM head, coil in a box

Post by DestructoMutt »

how do you explain that the water vapor stays at the bottom of the column? and that the ethanol vapor, if given the chance, makes it out the top of the column?

i think i understand the differences between the various types of columns (continuous, batch; pot, refractionating, compound refractionating), and how they work, and how the various types of reflux heads work (liquid management, cooling management and vapor management). i thought i was answering questions and/or supplying information that was missing or being passed along and inaccurate.

removing a reflux condensor from a compound fractionating head makes the head inoperable.

a vapor head relies on: vapor production, that a vapor/gas expands to fill it's container, and that the vapor will "split" based on the openings available for the expansion. the vapor that goes to the reflux condensor affects the reflux ratio of the column. removing some of the reflux instead of returning it to the column (per your thought experiment) changes the reflux ratio.

switching the order of the heads, would still screw up the reflux ratio.

snuffy, thank you for the pm. when does a theory about a process stop being a theory? or how about, if a process is thoroughly understood and people are inaccurately discussing the process or postulating theories that are wrong, and someone attempts to provide the correct information, does that make the accurate information a theory that's open for debate? nixon and mccaw's book "the compleat distiller" is good. they cover some difficult, techincal topics in an easy to understand method. it's not complete, but it is good for getting the basics and some of the intermediate science.
decoy
Rumrunner
Posts: 676
Joined: Fri Jan 06, 2006 4:21 pm

Re: Compact VM head, coil in a box

Post by decoy »

Destructomut said:
i think i understand the differences between the various types of columns (continuous, batch; pot, refractionating, compound refractionating), and how they work, and how the various types of reflux heads work (liquid management, cooling management and vapor management). i thought i was answering questions and/or supplying information that was missing or being passed along and inaccurate.......

...
snuffy, thank you for the pm. when does a theory about a process stop being a theory? or how about, if a process is thoroughly understood and people are inaccurately discussing the process or postulating theories that are wrong, and someone attempts to provide the correct information, does that make the accurate information a theory that's open for debate? nixon and mccaw's book "the compleat distiller" is good. they cover some difficult, techincal topics in an easy to understand method. it's not complete, but it is good for getting the basics and some of the intermediate science.
destructomut i think what you are missing is that we dont have anybody that has stood up until now and said i know evrything about it...
so what we are trying to do is have a discusion with others that know partialy what is going on in a VM head and try and understand thru discussion what is going on.

then we have you, you come in drop a partial answer which looks like it has been cut and past out of some form of electronic format. which is not wrong but it isnt compleet or missleading.

As you have self-professed to understand the principals and operation of all various processes, heads, columns and boilers perhaps you could take the time to start a thread and share your insight into the operation of a VM head.

as it was mentiond it gets very confusing when you get multiple theorys in the same thread..

That way we can read it and just ask you the questions about the things we need to understand better..

cheers..
snuffy
Swill Maker
Posts: 296
Joined: Sat Sep 13, 2008 8:21 pm

Re: Compact VM head, coil in a box

Post by snuffy »

At the risk of forking this thread up, I would like to briefly address the epistemological issue of reasoned speculation, synthesis of hypotheses and the evolution of theories.

There is a progression from speculation to theory. Most of the theoretical discussion on this forum is reasoned speculation based -- to a greater or lesser degree -- on experience, knowledge and observation. The next stage is formally stating a hypothesis as clear and as concisely as possible. There may be multiple competing hypotheses and they may be debated in an attempt to form a synthesis. Most discussion never reaches the stage of synthesis because of controversy over facts.

A hypothesis can be tested by experiment and observation. This requires independent investigators. The goal is isolating the fewest possible assumptions as controlled variables; reproducibility; precision; and accuracy.

Ultimately, the experimental testing of hypotheses leads to a falsifiable theory (in Karl Popper's sense). Having stood the test of independent reproducibility and falsifiablity, a hypothesis may be widely accepted as theory.

The earliest and most elegant example of this process can be seen in the writings of Galileo. Beautiful writing, elegant expression, razor-sharp delineation of observation. Something to strive for.

To this end, I am building a micromanometer and will be publishing details of its construction and use.

Thank you for your patience. We now return to our regularly scheduled program.

*edited for grammar*
Time's a wasting!!!
rad14701
retired
Posts: 20865
Joined: Wed Dec 19, 2007 4:46 pm
Location: New York, USA

Re: Compact VM head, coil in a box

Post by rad14701 »

I honestly have to say that I'm not here to listen to long drawn out lectures on how things work and how someone stated in a book what they thought things worked... I'm here to help the craft progress, not to rely solely on all the "been there, done that"... If you don't make a wheel hop out of the rut you'll just remain in the rut...

minime has been breaking new ground by experimenting rather than merely pontificating someone else's words... He's been tossing theories around, and listening to those of others, without shooting them down like he's a know-it-all, and the puts solder to copper in an effort to find the real truths... That's where I come from too... I've spent more time tinkering in shops than some members have been on this earth... I've built heaps of scrap metal over the years by building off the top of my head... And I've had many successes along the way as well... Pencil pushing engineers don't make changes in this world, it's the guys that do the actual work that make the true discoveries - some of which have their glory stolen by engineers who reverse engineer the fact to the theory... Been a victim of that myself more than once... But I digress...

Maybe my new signature should be "Put solder to copper or shut the hell up!"... :twisted:
manu de hanoi
Site Donor
Site Donor
Posts: 798
Joined: Mon Aug 13, 2007 9:06 am

Re: Compact VM head, coil in a box

Post by manu de hanoi »

snuffy wrote: To this end, I am building a micromanometer and will be publishing details of its construction and use.
That wont be necessary, the thermometer works well for determining the ABV of vapors. Originally we needed an inline ethylometer for the liquid distillate, didnt we ? :)

I just tested the VM head, It's a bit strange, because it's very sensitive, less sensitive than LM, but still ... the opening ratio is about 1:1,5 , but most of the time the valve was almost closed, all the adjustments (between too fast and too slow) were only spanning a turn of the valve wheel (which is about 2mm span for the gate). The vent is mandatory (because I have a long narrow output pipe) and is made of copper to condense residual vapor escaping. A 1:3 opening would probably be more confortable valvewise. Or even less if you need a lot of reflux. In my case the column is 3 inches wide, 1,8 meters high. picture of the gorgon is coming
manu de hanoi
Site Donor
Site Donor
Posts: 798
Joined: Mon Aug 13, 2007 9:06 am

Re: Compact VM head, coil in a box

Post by manu de hanoi »

the gorgon
Attachments
da gorgon mon.JPG
da gorgon mon.JPG (25.79 KiB) Viewed 1899 times
decoy
Rumrunner
Posts: 676
Joined: Fri Jan 06, 2006 4:21 pm

Re: Compact VM head, coil in a box

Post by decoy »

how did it go ?
manu de hanoi
Site Donor
Site Donor
Posts: 798
Joined: Mon Aug 13, 2007 9:06 am

Re: Compact VM head, coil in a box

Post by manu de hanoi »

decoy wrote:how did it go ?
see 2 posts before
rad14701
retired
Posts: 20865
Joined: Wed Dec 19, 2007 4:46 pm
Location: New York, USA

Re: Compact VM head, coil in a box

Post by rad14701 »

manu, how close is your coiled condenser to your gate valve...??? Is there a chance that it is shock cooling the valve gate...??? Just this tossing out as an idea as it just popped into my head when looking at the photo...
manu de hanoi
Site Donor
Site Donor
Posts: 798
Joined: Mon Aug 13, 2007 9:06 am

Re: Compact VM head, coil in a box

Post by manu de hanoi »

That worry was mentioned before, the coil is about 2 cm away from the 6cm wide valve. And anyways I really dont have problems making the vapor go in
snuffy
Swill Maker
Posts: 296
Joined: Sat Sep 13, 2008 8:21 pm

Re: Compact VM head, coil in a box

Post by snuffy »

Are you satisfied with the rate of delivery?

Do you think a smaller valve would make the adjustment less sensitive?
Time's a wasting!!!
manu de hanoi
Site Donor
Site Donor
Posts: 798
Joined: Mon Aug 13, 2007 9:06 am

Re: Compact VM head, coil in a box

Post by manu de hanoi »

snuffy wrote:Are you satisfied with the rate of delivery?

Do you think a smaller valve would make the adjustment less sensitive?
Despite the 5 sec lag between adjustments and effect, I am satisfied with the rate, and the thing is workable. But a smaller valve (1,5 or 1 inch) would be less sensitive and thus more accurate i guess (remember the reflux path is also obstructed by the legacy boka slant plates). But...on a second thought the wheel would be smaller giving less control and the step of the screw that controls the gate might not be smaller in proportion with the gate size :o too many parameters... :D
rad14701
retired
Posts: 20865
Joined: Wed Dec 19, 2007 4:46 pm
Location: New York, USA

Re: Compact VM head, coil in a box

Post by rad14701 »

Hmmm... Again, just tossing out a hypothetical... Do you think there is any possibility that the Bok slant plates are causing part of the lag you are getting due to that part of the column needing to re-adjust its equilibrium...??? You're running that component in full reflux mode, right...???
manu de hanoi
Site Donor
Site Donor
Posts: 798
Joined: Mon Aug 13, 2007 9:06 am

Re: Compact VM head, coil in a box

Post by manu de hanoi »

rad14701 wrote:Hmmm... Again, just tossing out a hypothetical... Do you think there is any possibility that the Bok slant plates are causing part of the lag you are getting due to that part of the column needing to re-adjust its equilibrium...??? You're running that component in full reflux mode, right...???
The moon was almost full, the light reflected by the moon on the condenser might have impacted the encabulator efficiency and dephased the leverage provided by the valve.



...or so am tole
rad14701
retired
Posts: 20865
Joined: Wed Dec 19, 2007 4:46 pm
Location: New York, USA

Re: Compact VM head, coil in a box

Post by rad14701 »

manu de hanoi wrote:The moon was almost full, the light reflected by the moon on the condenser might have impacted the encabulator efficiency and dephased the leverage provided by the valve.
Yeah, you'll have that... :roll:
snuffy
Swill Maker
Posts: 296
Joined: Sat Sep 13, 2008 8:21 pm

Re: Compact VM head, coil in a box

Post by snuffy »

Do you collect tails through the LM head? If so, what's the %abv when the VM head stops producing?
Time's a wasting!!!
manu de hanoi
Site Donor
Site Donor
Posts: 798
Joined: Mon Aug 13, 2007 9:06 am

Re: Compact VM head, coil in a box

Post by manu de hanoi »

snuffy wrote:Do you collect tails through the LM head? If so, what's the %abv when the VM head stops producing?
it never stops, its a continuous column
snuffy
Swill Maker
Posts: 296
Joined: Sat Sep 13, 2008 8:21 pm

Re: Compact VM head, coil in a box

Post by snuffy »

!!Continuous!?!?! :oops:
Time's a wasting!!!
Post Reply