Expansion chambers/bulbs

[Drunk-N-Smurf]

I'm toying with some ideas involving stacked expansion chambers, but aside from the fact that they slow the vapour speed down, I can't seem to find anything on the forums that says whether or not expansion chambers are good, bad, or otherwise.

Would like a little bit of a theory lesson on them if someone wouldn't mind?

I've come across a bunch of copper full sphere bowls, and was thinking of having 3 expansion bulbs, each one about a foot apart on my column, and either starting with the largest, (5" bowl at widest point) and working my way down to the smallest(2.5" bowl) or smallest to largest.

Look forward to the responses!
DS

[GuyFawkes]

I have never tried one for myself, but they are good for reflux. Allow some cooling due to the expansion, and I would imagine will slow down your run as well (like most reflux will). I think they look real purty, but if it's reflux you're after, why not just go with some packing? Much simpler and easier to tweak with if you don't like it right off the bat.

I know someone on here had a pretty neat thread about em...... not sure I'd be able to find it though

[newbyprepper1970]

From what i understand out of the reading i have done here enlarging the diameter of the column will slow the vapor speed and increase the reflux, The copper spheres you have found sound very interesting, they sound like something i saw on some pics on here from a commercial scotch distillery. My only concern is that they are manufactured for some other purpose and are not food grade (ie) they contain leaded sauter . If they are not then I would use one about a fifth of the total column height below the take off point that should allow plenty reflux below take off and still give a good product production rate i think. That is just a guess from the picture i saw of a pot still with a "bubble" near the top. Some packing below it and a cooling condenser above it and you might make a nice short reflux still, add a product control valve and a secondary condenser and you would really have something that looked neat! I am no expert, I am new to this, some of these ppl here are way more experienced than i am and smarter too, so lets see what they say. Oh and one other thing. They always refer back to KISS (keep it simple stupid) Have fun and above all be safe

[Dnderhead]

"enlarging the diameter of the column will slow the vapor speed and increase the reflux"
very little reflux if any will take place , the purpose of the "bulb" is a expansion.
if foam etc. comes up the riser it expands there instead of going up the riser. much like when a pot boils over and you remove the lid.

[Odin]

A well build "onion" will give you extra reflux. Do you want that? Depends on your goals. Running a low abv wash, you get a higher abv. But maybe you still need to run twice, taking cuts on the second distillation cycle? What I mean to say: it all depends on your goals. What are you aiming at? What is your starting point?

An "onion" works. May add up to half a distillation extra. And slow things down at the same rate it is upping the abv.

But the crux is: run your rig slowly. That's when an expension chamber works. If you run her fast, it doesn't make that much of a difference.

Other aim: it enhances likker/copper contact, if you use a copper onion. If your goal is to get rid of sulphers ... that might be a good thing.

Odin.

[bellybuster]

not gonna pretend to know anything about this but have a thought. if your onion is just an empty globe won't it reach (eventually) the same temp as the column/pot head and really have little to no effect???
i do get them if they have a plate inside like Mr P's bot globe thingy

Gotta add.
if there is indeed some reflux from it without some packing or something the refl;ux would just go back to the boiler, this would have no effect at all on the outcome....would it?

[GuyFawkes]

not gonna pretend to know anything about this but have a thought. if your onion is just an empty globe won't it reach (eventually) the same temp as the column/pot head and really have little to no effect???
i do get them if they have a plate inside like Mr P's bot globe thingy

Well not quite. It has to do with pressure more so than temperature. Just like how compressed air in those cans is at room temp in the cans under high pressure, when you release it out into the lower pressure environment it drops down in temperature and is very cold. To a much, much lesser extent, that's kind of what happens. The alcohol vapor is coming up off the pot and pressurizes a tiny bit in your column. In the bulb it suddenly expands out and drops in temperature. Mind you it's a very minute amount, not anything you would be able to detect with just your senses, but it's enough to cause some of the lower abv vapors to re-condense (ie, reflux).

Gotta add.
if there is indeed some reflux from it without some packing or something the refl;ux would just go back to the boiler, this would have no effect at all on the outcome....would it?

Packing would help it, but you don't need packing to create reflux. I'm sure I'm butchering the explanations here as I'm certainly not an expert, but it's kind of like creating a more difficult journey for your little alcohol molecules. The more cooling they have to overcome to make it out of the still, the more "excess" they have to strip off in order to do it, and the purer they are. It's kind of simple way to think about. In pot stilling, the cooling from an onion or packing basically cools the molecule to the point of forcing it to shed off some of the excess "stuff" with it, but doesn't fully condense the alcohol.

[bellybuster]

yes I understand the Bernoulli principle, just figure at such extreme low pressures the effect would be minimal if at all in stills/columns as small scale as ours. I would think to have any effect you'd have to start with real pressure.

I also get that there would/may be some reflux by definition but the redistilling like in packing is not taking place if it just runs back to the pot. it has no redistilling time like it does on plates or packing.

Don't mind me, just rolling stuff around in my brain cell.

[GuyFawkes]

Okay, I didn't mean to come off as patronizing either, I suck at explaining and I've been told I can come off that way.

Anyway you'd be amazed at what little things can have an effect. But I don't believe the temperature of the onion itself would matter much, and its effects have been observed before. It matters A LOT to how big your chamber is too. If you have a tiny little expansion chamber maybe twice the size of your column, you aren't going to see much effect. But if you put a pretty sizable bulb on there it will definitely give you some reflux.

[Dnderhead]

"it will definitely give you some reflux.
very little.

[Drunk-N-Smurf]

So, realistically they just look cool then? At least on the small scale?

[GuyFawkes]

And possibly give you a bit of reflux and protection from puking. But mostly they just look good. Either way, I think they don't have enough of an effect until you go commercial-scale.

[Odin]

They look cool, give you extra copper contact and extra reflux.

To get an impression. If I use my normal potstill head and make calculations on the parent site on how my run is going, I need to fill in 20% passive reflux to get it right. For my alambic, with an onion, I need to up the refluxpercentage to 50%.

Odin.

[bellybuster]

Okay, I didn't mean to come off as patronizing either,

didn't take it that way at all. I like these discussions as they tend to fill in empty spots where I think I might have the idea but am not sure.

Here's how I understand it. Look at my pot head. It is 1.5" up for 24" then off into the lei big. As the 24" heats up from bottom to top I figure there must be some reflux happening as the top portion is cooler. The reflux (what little there is ) is simply running back to the pot. Not getting any benefit. as the column heats up fully that little reflux stops due to the column being the same temp as the vapour. Continual heat input ensures this.
Now toss an empty globe into the same column. You will I'm sure get some cooling effect due to the drop in pressure when the vapour gets to the globe, not to mention the longer heat up of the globe itself but without some means to keep that little bit of reflux in the vapour path there would be no benefit??? It would simply drain down into the boiler. I still doubt that little pressure drop would be enough to cause condensing at all.
Plus, without means to force reflux you won't have enough to actually have a noticeable effect on the product??
Now, take the same globe and put a plate or packing or something that will "hold" the reflux in the vapour path. Still very little effect due to the miniscule amount of reflux. Without forcing additional reflux the effort is wasted.??

As I said, I really don't know, i'm simply stating what I think may be the result. I would like to know though.

I think the globe would be better utilised as an inline thumper. If I had one of these globes I would try it

[GuyFawkes]

didn't take it that way at all. I like these discussions as they tend to fill in empty spots where I think I might have the idea but am not sure.

Good

Now toss an empty globe into the same column. You will I'm sure get some cooling effect due to the drop in pressure when the vapour gets to the globe, not to mention the longer heat up of the globe itself but without some means to keep that little bit of reflux in the vapour path there would be no benefit??? It would simply drain down into the boiler. I still doubt that little pressure drop would be enough to cause condensing at all.

I think you are just confusing pot still reflux with fractionating column reflux. At least in the way I imagine it is happening, the hottest vapors contain the most energy, and when you present a little cooling to a group of the vapors, the ones with the highest energy will lose the most. This means the less energized vapors, the alcohol ones, will keep going on their merry way while the more energized ones will lose too much and will re-condense. Again, this is a stab in the dark, I could be absolutely 100% wrong, but all I know is that adding just a touch of cooling in a pot still DOES add some reflux and does result in a higher proof regardless of the presence of packing. I don't have scientific evidence, just personal, but if needed I could try some experimentation on my still to see the effects.

[blind drunk]

They seem to like theirs -

http://www.sasky.com/booze/2012/01/19/pot-still/" onclick="window.open(this.href);return false;" rel="nofollow

[okie]

I love looking at those Scotch stills. I am with Smurf. I want an onion on my still.

[Andy Capp]

Would a chamber operate in a similar manner as a dephlag but to a far lesser degree? That is to allow the higher alcohols past and send the lower ones back. With a proper sized dephlag, this is controllable from total reflux to none at all, but the expansion chamber would be influenced by outside temp/design/size/power input and lack control of sorts. Any reflux would be minimal but in a potstill producing flavoured spirit this would be an advantage. I like the idea of the chamber and think it could only benefit a pot still rather than hinder it. I intend to build one anyway just to see how it goes. Was thinking about installing it above the thumper output to see how much more heat, if any, can be thrown in without pulling tails.

[GuyFawkes]

That'd be my estimation Andy. I'd say it's comparable to a very very weak dephlag that can't be controlled, at least in terms of reflux. Maybe it would be worth attaching two otherwise identical columns to a boiler, one with an onion and one without, to see. Now wouldn't that be something to see

[Angel_Kefka]

I would think it would have some effect. A vigreaux column is basically a bunch of bulbs the whole way up and its purpose is reflux. The question is will it be noticable with just one chamber at the size of your column. I think how fast you try to run will make a big difference there, high enough initial vapor speed and it will go right past it, but slow enough should have some effect.

Then again I've thought that given the time and materials it would be interesting to to build a vigreaux out of 2" pipe and copper globes about 6", maybe 8 or 10 high. Would look cool and be interesting to see if it carried much flavor for the amount of reflux. Probably never happen, but I come up with all kinds of crazy ideas.

[Dnderhead]

Does not a vigeaux have protrusions on the inside?

[bellybuster]

I'm starting to see the light.
The vigreaux column doesn't compare, it is cased by a condensing tube. They act very similar to a plated column.

[Dnderhead]

"They act very similar to a plated column."
I believe so.though im not a engineer.
Iv read many articles on the "bulbs"
1)some say for reflux (it mite some?)
2)some for flavoring,(the originals was used for gin etc.,does not sound right as how would you git the herbs in there?)
3)this sounds the best,,to stop the foam from coming over. as the foam rises it expands in the "bulb) collapsing the bubbles ,then it drains back into the boiler.the "cap" on a simple pot still does similar if its big enough.this would cut down on needed head space.

[bellybuster]

this is a good discussion, I'm glad it has not been derailed like usual.
I am now wanting to find me one of these. I've been thinking about an inline thumper and I think one of these would be perfect. My problem is I'm too damned cheap just to buy one.

[claytonhaske]

i read somewhere that the bubbles help with the flavor of malted spirits like rum, or any thing with malt in it.

[GuyFawkes]

Malted spirits like rum.....? You're going to have to explain to me how rum is malted

I believe large distilleries have them because they do offer some reflux at that scale. I'm not sure how much volume they add, which is what would make them for stopping puking as dnderhead mentioned, unless I am misunderstanding. At our scale though, I have a hard time believing they'll do too much other than look real purty...... perhaps discourage puking, perhaps offer a little bit of reflux, perhaps just be more copper in the vapor path. Since I haven't seen anyone using these with scientific results, I don't think we have quite enough information to say what they will really do at hobby scale.

[TheRevDr]

3)this sounds the best,,to stop the foam from coming over. as the foam rises it expands in the "bulb) collapsing the bubbles ,then it drains back into the boiler.the "cap" on a simple pot still does similar if its big enough.this would cut down on needed head space.

I've seen this first hand while using glassware in the lab. An expansion chamber works great to prevent a foaming solution from foaming up into the narrow section above it. A far as reflux, there might be slight reflux during heat up but there is slight reflux on any surface during heat up. I have never seen more in an expansion chamber than just on the side of any other surface, and I have boiled/evaporated/distilled more than my share of solutions in the lab with glassware enabling me to see what was happening.

[rad14701]

Anyone wanting to experiment with this can do so by combining two of the concepts we already use here... Many here have seen how liebig condensers have had the vapor tube crimped for added cooling... And they have also seen concentric pot still heads, which I also run as a concentric reflux head... Combine the two and see what happens... A concentric reflux head with a crimped vapor chamber... Food for thought...

[GuyFawkes]

According to this video http://youtu.be/Jx5Vrh5Mg3c?t=5m20s of the Glengoyne distillery, they use the bulbs for a little reflux and for copper contact, or at least that's what the guy brought up.

I think for the most part we have the gist of it. It will present a bit more surface area of copper, a bit of reflux, and a bit of protection from foaming. The bigger the bulb, the more pronounced its effects. As to exactly how much, the variables will probably be infinite. I'd bet how hard you're pushing the still would be among the biggest factors.

[Dan P.]

Interesting topic.
My thoughts;
I have (unintentionally) made flavourless vodka on a full-blast stripping run on my pot-still. In the spirit of full disclosure, it was a pretty flavourless wash, but even when I am going for maximum flavour, people who have tasted my product have suggested it's a little bland. So to say that an expansion chamber has no or little effect makes about as much sense (to me) as saying that brown dogs are faster than white dogs. It depends on the dog! My pot still goes from around 400mm in the boiler, with maybe 300mm head space, and is necked down to about 200mm where it joins the cap. The cap is about 300mm in height, and about 300mm at its widest. Over all the distance between the top of the wash and the top of the cap is about 2/3rds of the depth of the wash. This is very different from a length of 1" tube coming out of a keg. You would need a pretty big ball to mitigate the pressure caused by those latter conditions.

Anyway, my theory is that "reflux" happens within the vapour. That means that those compounds which evaporate at temperatures below their boiling point will cool to a significant degree on their way up the (wide, slow) vapour path, and, if they do not condense, then the lack of pressure will allow the particulates to fall back down and away from the lyne (beings, as they are, denser). Of course, my understanding is primitive, but I am imagining a sort of fractionating tower for the vapour.

I also observe that when my still is heating up, the vapour delays in the boiler for some time, before moving into the cap, where it also delays, until finally it moves into the lyne, at which point it is only a few minutes till distillate starts being produced. I believe (theory, not fact) that when the vapour is delayed in these two separate places more reflux/rectification/fractioning is caused.