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This has always interested me . A lot of guys use a Boka in stripping mode ...IE ...no reflux ..collect all . Others use their CCVM column in Pot mode .

Now a lot of us would say all that packing is going to cause reflux and that is should be removed when using such a column as a pot still .
How about the Height of that Riser ? Again I often hear folks saying that a tall riser .....say 3-4' ( about a meter ) will cause passive reflux .

So the questions I had were does the tall riser really cause that much passive reflux that its noticeable ?
Does having that riser full of packing make a noticeable difference ?
Does insulating the column in both cases make any difference ?

Thanks to Salty asking a few questions elsewhere I ran a few tests on some all Molasses wash I had .Now Salty's question was more along the lines of what is the difference between wash temp and vapour temp so that's where it all started for me .
So there are a few lead up tests .

While I have a wonderful Data logger and temp probes at work , I did this the old fashioned way with thermometers and a pad and pencil .

First I found my Thermometers and checked their calibration .I had two that seemed to track each other perfectly . As most of you know I aren't big on thermometers so I had to stick a couple of holes in my Boiler . I sacrificed my old Still Spirits 30 Liter boiler . It has a 2400 watt element in it now days . I used this for all the tests .
I wrapped the shafts of the thermometers in teflon tape so they are thermally insulated from the body of the boiler .... IE ...they only contact and measure the liquid or Vapour they are in contact with . I'll be using for the first tests my liebig . Its all rugged up with several blankets so to eliminate as much as possible any reflux . Here are the results of around 12 liters of water only in the boiler . Incidentally I have tank water and are about 50 meters above sea level .

Full power ( 2400 watts)
Boiler 100.4 degC
Steam 100.2 degC

I turned the power right down to a drip a second

Boiler 100.5 degC
Steam 100.2 degC

I removed the insulation , passive reflux ...on water

Full power

Boiler 100.4 degC
Steam 100.2degC

I turned the power down to a drip a second ( well actually it was the same setting on the controller as covered )

Boiler 100.5 degC
Steam 100.2degC

I guess no real surprises here . It's what we have always thought ......boiling point has nothing to do with power however I was miffed at the 0.1 degC increase in the boiler temp when it was turned down despite the steam temp staying exactly the same .

Anyways I was surprised that the passive cooling of the top of the boiler head space and riser didn't seem to alter the steam temp regardless of power ...even at a drip . It was incidentally a fairly cool 14 degC outside and there were a few gusts of wind .
It is interesting that there is a notiable difference between water boiling and water vapour temps .....and incidentally I swapped those thermomertes over just in case they were miss tracking and the results were the same . ...so it is what it is .

Be interesting to see with an alcohol mix how much this changes .

This time its with a real wash .
Note that the thermo's are in the liquid and the boiler head space , not at the top of the 500mm riser. ........these tests come later .

I collected about 250mls , took the temp readings and noted the ABV of the jar at that time . To be honest I was not as accurate with this run as the following but it gives a fairly clear baseline . You can see that while collecting the first jar there is a climb in vapour temp as the head space if purged of ambient temp air and filled with hot vapour . From then on the head space vapour temp and boiler temp pretty much follow each other then they start to diverge .
The Boiler temp starts to get hotter than boiling water . My reasoning for this is that the All Molasses wash I use is full of Salts ( as Molasses is ) and this is raising the boiler temp . The Vapour temp however is showing the real Water /Alc mix Temp . .

OK now onto the original questions about using a tall riser .

I used the 1 Meter Packed section off my 2" VM column . Its stuffed full of staino scrubbers . The Temperature outside where I'm testing is about 14 deg C .
I switched to my Shotty condenser because it was more convenient but I doubt that will make any difference .

Ah, this is very interesting! Thank you for providing measurments!

From my own experience I have answers for your two first questions:
Yes, a long riser gives noticeable passive reflux.
Yes, filling it with some kind of packing also makes a difference.

I have no measurements to support that, though.

This is the setup
1 meter riser UNPACKED

Un-insulated ......Here I hope that the winters day 14 deg will cool the tall column and allow some noticeable reflux followed by the same section Insulated and then wrapped up after photo was taken with several blankets to keep the heat in ...cold out. Note that this time the thermometers are measuring the boiler temp and the temp at the top of the column . The Thermo in the boiler head space is not being used and is just to plug the hole
So here's the results .
The boiler temps of both runs were Uncannily the same so There is only one red line for this . Now here are the results of that riser FULL OF PACKING ....again uncovered , so its exposed to the elements and then all wrapped up so hopefully the amount of reflux will be minimal.
Again the Boiler temps were the same so as above , one red line for the boiler temp

I'll let folk draw their own conclusions but from what I can see there is not really that much in it . To be honest I would have thought that a tall packed section exposed to a winters day would have shown heaps of reflux and a significant ABV increase but it wasn't as spectacular as I had thought .

Perhaps running outside in a blizzard might net different results , but I won't be there to find out .

So If someone was asking about using a packed column for stripping I would say go for it ...don't worry about ripping the packing out . However , wrapping a packed column in a blanket seems to give the same results as an unpacked column...Iff'n one was worried about such things .

Kareltje wrote:Ah, this is very interesting! Thank you for providing measurments!

From my own experience I have answers for your two first questions:
Yes, a long riser gives noticeable passive reflux.
Yes, filling it with some kind of packing also makes a difference.

I have no measurements to support that, though.

Pleased you were interested Kareltje .....Took two afternoons to do it ....luckily Mrs Yummy was away

But lots of unanswered questions I guess ...like running at a lower power .Will it be more effected by the passive cooling ?
Will a sugar wash track Liquid and Vapour Temps without the divergence that I got from a Rum wash ?
Will a Spirit Run give different results ? .

Oh to be retired and have a bit more time LOL .

I reckon to get a bit, tho' "Riser" is tall and thin 1m x1" so the vapour has a much better chance of touching the walls. It is also copper, which is a good conductor and I have a Dimroth in an offset of around 5", which I believe may be providing a bit of cooling.

I wonder whether a few turns of copper pipe with cooling water wrapped around the top of your column would have a significant effect ? - a bit like running it in a blizzed perhaps, but without the hypothermia !

I did a perhaps similar experiment a while ago:
Birdwatchers stripping runs insulated lid vs uninsulated lid and at different wattages. How the passive reflux affects the abv and taste. I didn't get measurable differences (°C/%abv), but the concentration of the foreshots smell with uninsulated lid at low wattage was impessive. Nothing I was able to see on the temp or abv, but it was obvious how an insulated still at high wattage spreads the fores through the whole run.

My experiment and experiments of other members are here:
viewtopic.php?f=15&t=58627

Yummyrum wrote:
So the questions I had were:
1) does the tall riser really cause that much passive reflux that its noticeable ?
2) Does having that riser full of packing make a noticeable difference ?
3) Does insulating the column in both cases make any difference ?

Past few days I did 3 stripping runs inspired by these questions. The wash was 7.5 l birdwatchers of 14.4 %ABV each time. I have a spiraled riser of 13 mm ID and over 3 m long with a working height for me of 50 cm. I added a second thermometer at the bottom of the spiral.
On the spirals I can put some wet rags, that work as an extra cooler, but of course I can wrap the whole spiral in some blankets or large towels to insulate it.
The runs were made at low energy input: 387 till 390 W. I sampled in pots of about 100 ml. Ambient temperatures were 30 dgr C for the fist 2 days and 26 dgr C the third day.
At the bottom and at the top of the riser I put a thermometer and after running corrected the readings: at the very end of the run 100 dgr C is 99.5 or 100 dgr C at the bottom but 102 or 102.5 dgr C at the top!
Apart from cooling vs insulation I tried to run in the same way as much as possible, but this of course was not a scientific test.

The temperatures on bottom and top were: We see that wrapping up the riser makes the temperature at the top equal to one at the bottom, with a small delay at the start. It seems as if the riser does not exist, temperaturewise.
Normally when running so slow there is a considerable difference between bottom and top, meaning there is a considerable loss of heat, causing passive reflux and thereby a rise in %ABV. In the end I got tired and fired up to drive out all the alcohol. In that case clearly the vapour speed is so high, that tha vapour does not have time enough to cool in the rising.
The effect of the cooling by wet rags is more difficult to explain, because this was done by hand and not very subtle. In drying the rags became less effective and right after wetting them the temperature at the top sunk and surprisingly enough this at the bottom too. At first I had 3 rags, but then the vapour could not reach the top. After some time I got bored by wetting the rags and thought I had proven the point, so I let them go.

The %ABV per sample during the 3 runs were: As we see the warm run looks like a pot still run, starting at 82 %ABV. Coming from a 14.4 % wash, this means that the 2.5 l empty space in the boiler and the small piece of exposed riser acts as one tray: 14,4 -> 62 -> 82.
The normal, naked riser adds another tray, starting at 92.5 %.
The cooled riser started at 92, but the next 4 samples were 94 %ABV.
(Measured at about 30 dgr C for the latter 2 and at 25 dgr C for the first run.)
The inconsistent treatment of the cooling is reflected in the curve of the samples, but I guess the point is clear.

I found a rather heavy stench in the heads, just as Der Wo said and I regret I did not keep the first samples apart.
And a funny thing I saw: regardless of the status of the riser the rate of alcohol collection was constant. Only the amount of accompanying water was different.
This reminded me of am earlier finding: regardless of how hard you run, it always takes the same amount of energy to distill a wash in a given constellation.

So at 1) Yes, a tall riser makes a difference, at least at low speed.
at 2) I do not know about packing, but another method of slowing down the vapour, namely cooling, does have a noticeable effect.
at 3) Insulating the riser makes it kind of disappear, makes it less effective.

Kareltje wrote:...Q - Does insulating the column in both cases make any difference?
A - Insulating the riser makes it kind of disappear, makes it less effective.

And to add to this result, the fact that the insulated column keeps the rising vapors hot, improves performance of a reflux stillhead where the vapors are condensed and the condensate drips back through the packing where the hot rising vapors transfer some of its heat back into the condensate, thereby reboiling (this is called “reflux”). This significantly improves fractionation as the volatile constituents continue to progress up the column while the constituents with a higher boiling point tend to sink lower in the stack.
ss

Just looking at it that worm does not descend continuously.
Try putting a ball bearing or a small marble in the top and see if it keeps moving downwards....

Geoff

The Baker wrote:Just looking at it that worm does not descend continuously.
Try putting a ball bearing or a small marble in the top and see if it keeps moving downwards....

Geoff

It looks that way, indeed. But that is caused by the contortion of the photo. Top and bottom seem to be bent backward.
But I will do your test to be sure.

Kareltje
Thanks for taking the time to carry out the tests and post .

I was intrigued by the funky bit in the curve on your ABV graph compared to my ABV graphs . At first I though whoo , you have the same as me then realized they were not the same .

Good stuff . Yes I also agree with you and der wo about the increase in initial fores/heads intensity when using a cool riser /coil ...in my case packed . I mentioned it Here where I said

but what I did notice while having a quick rub/sniff /taste was that the stripped jars from the uncovered packed section were seriously separated almost to the point where I might concider doing a Final cut on these jars . The usual
manky tails that normally smears from one end to the other was drastically reduced in the hearts section. There was an obvious Fores cut that you wouldn't normally see in a Stripping run .

Should have said it here too

Thanks for your efforts fellas. I've been wondering if a packed section would help with cuts.

Wouldn’t get too excited about it mako .

Without some reflux condenser above it , a packed section on its own won’t be the startling difference you might expect .
Subtle maybe , if tall and uninsulated , but not gonna smack you in the face worth it .

When I was a younger MoonBreath, I kept my single plate torpedo with 12" riser fully loaded via bucket of ice water and a dishrag..Made plenty reflux..Learned what reflux is, and decided accordingly on rc choice..Very good experience.
Larry Taylor turned me onto the technique.
# ragjockey.

I recently pot stripped some sugar wash and decided to leave my perf plates in this time. Pretty cool to actually see passive reflux happening in the form of a small bit of action on the plates.
I also noticed that the down comers were full of liquid. Such small amounts of everything. Obviously didn’t do much.

Yummyrum wrote: ↑Mon Nov 12, 2018 3:13 am Wouldn’t get too excited about it…..
…..not gonna smack you in the face worth it .

+1

Yummyrum wrote: ↑Mon Nov 12, 2018 3:13 am Wouldn’t get too excited about it mako .

Without some reflux condenser above it , a packed section on its own won’t be the startling difference you might expect .
Subtle maybe , if tall and uninsulated , but not gonna smack you in the face worth it .

I am still super new to this, having only done three runs so I have a LOT to learn. With all the work Yummyrum did, I can see that a column packed or not once the column equalizes in temp the reflux effect will stop. Why is it then that some have a really long column? As for myself I am just trying to work with all grain mash and make a high quality full flavor "bourbon" type spirit. With that I am overly concerned with a lot of reflux to get a high proof spirit. Right? I need some of that water to bring the flavor with it?

jpparts wrote: ↑Mon Jan 02, 2023 12:48 pm I am still super new to this, having only done three runs so I have a LOT to learn. With all the work Yummyrum did, I can see that a column packed or not once the column equalizes in temp the reflux effect will stop. Why is it then that some have a really long column? As for myself I am just trying to work with all grain mash and make a high quality full flavor "bourbon" type spirit. With that I am overly concerned with a lot of reflux to get a high proof spirit. Right? I need some of that water to bring the flavor with it?

generally reflux , packing and most tall columns are for making vodka or neutral with little to no flavor compared to a whisky or brandy . You are right in saying that you want to keep the flavor of the mash for all grain in the final product . the more your abv rises after a certain point the less taste there will be ,

The very tall columns you see stop the column equalizing in temp by having a condenser at the top which sends distillate back down the packing . The height does help to keep temperatures different though as its further away from the boiler making it easier to make 95ABV alcohol seeing as the combination of packing , height and forced reflux means the alcohol is getting re-distilled in the column many times

by controlling the reflux condenser the amount of alcohol vapor being let past to the second condenser (product condenser) can be set . once it reaches the second condenser its turned into liquid and drips out

some traditional style stills for whisky or other flavored spirits use a bit of reflux due to the shape by having a tall riser or shaped chamber for vapour but this is passive reflux not forced . And packing is not used in these

Keep studying , there is a lot to learn but it seems like you are getting there

jpparts wrote: ↑Mon Jan 02, 2023 12:48 pm Why is it then that some have a really long column?

Sometimes, like on my still, it is to get the condenser away from the side of the pot and to give enough height to run my take off away from the pot