Concentric Build

[thisguy]

Hey Guys,

Ive always wanted a reflux still, without having to try to wind a coil or having a monster column. So in doing some research, I stumbed upon Rad's and Pyewacket's concentric reflux/pot design. Turns out I had all the parts minus a few caps and a reducer, so I made one today! Got done with it about an hour ago.

I think i turned out really nice. I have to add a few more things to it including a Needle valve, some more 1/4" pipe (and a better way to cut the stuff) for water cooling pump connecters, and a smaller pump.

Im guessing most of you know how it works, but for those who are researching heres the down low:

From the top:
Cold Finger - 12" x 1/2" copper pipe. 2, 1/2" caps at each end. The cap on the top has a 1/4" hole drilled in the top for the incoming water for the cold finger. Stuck threw the hole and soldered into place is about 10" of 1/4" copper tube. Then two inches from the top, drilled a 1/4" hole with 1/4" tube soldered into place for the output of the cold finger.

Then theres a 3/4" cap going over the 3/4" copper tube. A hole is drilled into the cap big enough for the cold finger to slide into it, so a little over 1/2" hole. I did not solder it to the cold finger, just incase the condensers cant keep up. However, the cap is soldered onto the 3/4" vapor tube.

The 3/4" vapor tube runs through a 1" copper tube which pretty much acts as a liebig condenser. The 3/4" copper tube is where the vapor travels. The 3/4" vapor tube is soldered into a 3/4" hole drilled into a 1" cap that goes over 1" copper jacket (the thing thats pretty much like a liebig condenser). The 3/4" tube pertrudes from the 1" cap about .5". EDIT: I forgot about the copper wire wrapped around the 3/4" tube; it creates turbulence in the water flow going around the vapor tube.

Then at the bottom is where the reflux is going to happen. Its about 5 1/4" x 1/2" of copper pipe. Then 1" from the bottom theres a 1/2" x 3/4" reducer slid over it, that acts as a product well. In the side of the 3/4" portion of the reducer is a 1/4" hole for product output. Make sure to drill holes into the 1/2" reflux throat just above the product well (the 3/4" x 1/2" reducer). The holes will allow the vapor to flow out of the reflux throat and allow the condensed product to flow back into the boiler.

Its not done yet, I have to add a 1/4" needle valve for product output, get a little smaller pump than what I use for my original pot still with liebig setup and some 1/4 inch hose. 1/4" tubes connecting to the jacket, and a 1/4" product output with that needle valve. Im also going to add a 10" x 1" packing tube to it at some point. Thatll have a 1/2" x 1" reducer on it going to the 1" packing column, then a 1" adapter to connect to the boiler. And im going to put a thermometer port in the 1" column under the 1/2" reflux throat.

Let me know what you guys think!

[live_free]

just being curious ( and have done no research on this style of column). what size boiler would this column be used for? was thinking of building a small reflux still for feints run and this design is intriguing

[thisguy]

I'm using it on a 5 gallon SS pot, usually only fill it up about 3-4 gallons. Check out Rad and Pyewackets builds too. They know more about this stuff than I do.

And the set up as-is, is mostly a pot still set up. Yah if the needle valve is closed or slightly closed itll reflux back into the boiler, but for proper reflux a packed column or a slanted plate column is needed for full reflux capabilities. Which I will be making in the near future.

Also, i havent tested this yet. The only testing ive done is make sure its water tight.

[thisguy]

Heres the drawings (or scribbles) I did for it. Hope it makes sense/you can read my writing.

The cold finger is marked with the slashes going through it.

[live_free]

right on. off i go into the abyss again. thank you.

[thisguy]

Hahaha, thats a good way of putting it.

[rad14701]

It doesn't appear as though you calculated in a collection cup area for the condensed spirits to reside in until the cup fills and reflux returns to the column... Or what little there is isn't big enough... It can be tough getting a large enough collection volume in concentrics which is why the center vapor tub can extend 4" - 6" up into the vapor chamber... Not a problem for pot still mode but can be a major problem in reflux mode...

[ben stiller]

I am building a 1.5" by 1.25" by 1" column. Planning on a 2oz collection cup. Does this sound correct? Also what is the suggested
height of the center tube extending into the vapor tube for best reflux? I plan to make it modular with several length tubes so I can
experiment with column heights.

[thisguy]

It doesn't appear as though you calculated in a collection cup area for the condensed spirits to reside in until the cup fills and reflux returns to the column... Or what little there is isn't big enough... It can be tough getting a large enough collection volume in concentrics which is why the center vapor tub can extend 4" - 6" up into the vapor chamber... Not a problem for pot still mode but can be a major problem in reflux mode...

Okay, so i have to make the collection chamber bigger, and extend the center vapor tube about another inch into the vapor chamber?

[still_stirrin]

What is the volume of liquid in your annular cup?

I made mine between 3 and 4 ounces. Too big and you'll get more smearing. Too small and you don't retain much to draw off, slowing the liquid takeoff. Remember, it's a liquid managed reflux head.
ss

[thisguy]

I keep forgetting its an LM...

About half an ounce. Based off what I found, I need about 2 inches of 3/4" pipe for a collection cup to get just over an ounce? Is that correct?

[thisguy]

So if im taking the suggestions correcet, I need to make a new 1/2" reflux throat.

Make it a good 6" long, with the holes for reflux drilled about 2-3 inches above the 1/2" x 3/4" reducer that acts as the collection chamber? So, for visualization sake, pretend the picture of the throat in the first post is 6 inches long...I should have the holes ~3" above the reducer? So that way about 2 oz of distillate can collect before falling back into the boiler.

[still_stirrin]

Why do you need holes? The liquid will simply spill over the rim when the cup is full. Make the cup deep enough to collect the desired volume.

And while your cold finger is great, I (like Rad) don't think you'll need it. I just put a ball of SS scrubbie in the top and everything condenses inside the condenser.

One key feature of the concentric is the thermodynamic changes due to vapor velocity differences through the venturi (throat tube) and the condenser inner tube. When the vapor slows down, it expands and liberates heat, causing it to condense along the walls. The liquid then runs down the walls pulling more heat out of vapor by conduction. Its an incredibly efficient design...much more than a twisted coil.
ss

[rad14701]

Due to the small volumetric area between the tubes the vapor tube will need to extend higher into the condenser than one might think... My first concentric, with the integral collection cup, has the vapor tube extending almost 4" in order to hold 1oz of spirits... I measured as well as calculated collection cup volume...

[still_stirrin]

Hey thisguy,

I just did a quick volume calc for your cup and with 1/2" inside of 3/4" pipe you need 7.35" of cup to hold 1 ounce of liquid.

FYI- 1 oz = 1.804 cu.in.
the area of the annulus is pi/4 x (.75^2 - .5^2) = .24544 sq.in.
length needed is 1.804/.24544 = 7.35"

A larger condenser would hold more volume. Again, mine is 1" in a 1.5" shell. I can get an ounce of liquid holdover before reflux spills over the cup.
ss

[thisguy]

Why do you need holes? The liquid will simply spill over the rim when the cup is full

Yesterday before I got all this information I soldered a cap over the throat to prevent any of the reflux from falling straight through the throat off the cold finger and into the boiler.

And while your cold finger is great, I (like Rad) don't think you'll need it. I just put a ball of SS scrubbie in the top and everything condenses inside the condenser.

Okay, ill stuff some scrubbies in there. But im going to shorten it according the the 7" reflux throat info still_stirrin' gave me, just in case i need it.

Hey thisguy,

I just did a quick volume calc for your cup and with 1/2" inside of 3/4" pipe you need 7.35" of cup to hold 1 ounce of liquid.

FYI- 1 oz = 1.804 cu.in.
the area of the annulus is pi/4 x (.75^2 - .5^2) = .24544 sq.in.
length needed is 1.804/.24544 = 7.35"

A larger condenser would hold more volume. Again, mine is 1" in a 1.5" shell. I can get an ounce of liquid holdover before reflux spills over the cup.
ss

Okay! Thanks for that stirrin'. If I had the funds, I would go and up the jacket to 1.25" and go buy the proper fittings to make it work; but i dont right now so well make this work. Some useful information right there. So ill make the throat 7.5", put the 1/2" cap back on it and drill some holes for reflux. Unless you guys really dont think the holes and cap are necessary. I was PMing pyewacket earlier and he pointed out that without the cap one might get some passive reflux off the cold finger/scrubbies.

[thisguy]

Thanks for the input too Rad and stirrin'. Very much appreciated. Along with the lesson in engineering and physics haha

[Kegg_jam]

Dang. I just checked my reservoir and it is only holding 30ml or about 1 oz.. Seems I miscalculated.

I'm running 1.5" over 1.25" over 1" in a double reducer setup.

[thisguy]

All im going to be able to do is 1 oz. After rereading radz concentric build thread, he said 1-2oz is fine.

[still_stirrin]

thisguy,

I wouldn't even bother with the cap and holes in your throat tube. Just size the length as needed (7 to 7.5 inches) and you'll be good to go.

The primary site for reflux is along the walls of your concentric condenser. Probably some on the cold finger too, although it won't really be needed to manage your reflux. Reflux is what you're trying to do here, so it is desireable. If it drips back down the column to the boiler...so what? That's what helps refine your spirits. The LM is using the condensate to manage the reflux ratio but adjusting the liquid takeoff. If it condenses faster than the takeoff rate, the liquid will spill over the inner tube back down the column. That's how it works.

I believe your LM head will run perfectly fine without the cold finger. Try with and without to see what you learn as far as how it runs.
ss

[thisguy]

I ended up seeing that post a little too late stirrin'

It has the cap and holes, but I dont see that as a huge problem. Either way it will reflux back into the boiler. Heres the pics of the new and improved version. Measures roughly 7.25 inches from collection cup to the first hole.

I also pickled the needle valve.

EDIT: I removed the cap.

Pics:

[thisguy]

Another question: would you guys recommend soldering the condenser to the reflux throat, or leave it detachable?

[Pyewacket]

Considering how high up you are going with your return stem-up...I would solder it; not sure a slip fit would hold the distillate.

Mine only went up 1/3rd as high as yours...and I soldered mine.

[thisguy]

Okay Ill solder it. Im doing both cleaning and sac runs tomorrow out of it. Might even do a real run if I have the time. I plan on spending all day on the still. Looking forward to it.

[rad14701]

thisguy, I'm a bot concerned over the fact that your coldfinger is almost touching the vapor throat... In doing that you aren't leaving much room for vapor expansion and collapse... I'd only have that coldfinger go halfway down, or try running without it...

[live_free]

glad i tuned back in

[thisguy]

thisguy, I'm a bot concerned over the fact that your coldfinger is almost touching the vapor throat... In doing that you aren't leaving much room for vapor expansion and collapse... I'd only have that coldfinger go halfway down, or try running without it...

Okay. Ive done a cleaning run, a sac run and a run of a sugar wash through it and didnt have any problems.

What would not leaving room for the vapor to expand and collapse do?

[still_stirrin]

Lower efficiency. And cost more (although already a sunk cost).

Like I said in an earlier post, the vapor speed slows down once thru the throat because the area increases. That slowdown increases the static pressure and raises it above the vapor pressure initiating condensation. If you don't understand this, you're not thinking like an engineer.

Leaving the cold finger inside causes the flow area to remain smaller and the vapor velocity remains higher, at least until the temperature difference cause it to condense. There's more to thermodynamics than simply temperature here...there's also dynamic pressure and the vapor properties.

I still don't think you need a cold finger. Try without it.
ss

[rad14701]

thisguy, I'm a bot concerned over the fact that your coldfinger is almost touching the vapor throat... In doing that you aren't leaving much room for vapor expansion and collapse... I'd only have that coldfinger go halfway down, or try running without it...

Okay. Ive done a cleaning run, a sac run and a run of a sugar wash through it and didnt have any problems.

What would not leaving room for the vapor to expand and collapse do?

If it's working well then it might be alright... Part of the efficiency of earlier concentrics revolved around the compression of vapor within the throat eventually expanding in the condenser chamber... The expansion acts as a method of cooling... That being said, if you were to try increasing the volumetric area within the chamber, by raising the coldfinger, you might find that cooling efficiency is improved... I'd be interested in hearing your findings along those lines...

Posted the same time as still_stirrin...

[thisguy]

Lower efficiency. And cost more (although already a sunk cost).

Like I said in an earlier post, the vapor speed slows down once thru the throat because the area increases. That slowdown increases the static pressure and raises it above the vapor pressure initiating condensation. If you don't understand this, you're not thinking like an engineer.

Leaving the cold finger inside causes the flow area to remain smaller and the vapor velocity remains higher, at least until the temperature difference cause it to condense. There's more to thermodynamics than simply temperature here...there's also dynamic pressure and the vapor properties.

I still don't think you need a cold finger. Try without it.
ss

I understand it, It just didnt dawn on me. I was thinking in terms of a more direct cooling. What I mean by that is using the jacketed cooler and the cold finger as opposed to the indirect method of just letting vapor do what vapor does in terms of expanding and cooling. I have two washes to run this weekend, Im going to do one of them without, maybe both the cold finger and see what happens. I honestly feel safer with the cold finger just incase something unforeseen happens.

@Rad: in terms of efficiency and based off of only two runs(excluding the cleaning run, but including the sac run) ive done with a cold finger in; I got ~200Ml every 10-15 minutes. I dont know if thats good or not? Thats with the valve set so that it drips 3-4 drops per second.

In the last run I collected 1 liter total in about an hour. I had to resort back to propane as Im waiting for my new electric controller to come in the mail (thats why im using the cold finger so much right now). So heat up time took a while. That liter was about 55% (110 proof). First 250Ml was about 74% (148 Proof) I ended up shutting it off once the last 250Ml got to 100 cause I had to go to bed for work in the morning. That mash was screwed up to begin with and I made these first few ferments with the intention of getting to know how to run the still.

Everything seems to be working just fine with the cold finger extending down to the reflux throat, as far as I can tell. Im really pleased with the design. I certainly wasent expecting to get a liter of 55% out of that wash. When I do the run a run without the cold finger ill let you know what happens. Ill probably do a few runs with it out just so theres more to look at. But that will probably be once I get my controller set up so i dont have to worry about any explosions or anything.

Even if I reduced the cold finger by half, would the 3-4 inches of empty space be enough to make a difference in terms of the vapor expanding and cooling that way?