Musing about my Liebig performance

[Andrew_90]

I have a 35/22mm OD Liebig with large water ports for a 30 litre kettle. So the first thing that struck me was that the cooling efficiency appeared worse that on the 7l kettle and still I built for my son which uses 22/15mm OD for the condenser. And yes, the one has a 54mm column while the other is 22m so there is way more thermal mass flowing through the large still. I still can’t help wondering if I missed a trick.

As my Liebig is designed to operate at circa 30° from the lateral and with the benefit of hindsight; I believe this perceived poorer performance can be attributable to a couple of things.

The first being that I have way too much capacity for the water around the inner tube, this I believe is causing dead spots where warmer water accumulates. In a vertical Liebig this point is mute as the water will percolate up equally. I though the more water I had the better, counterintuitively I believe this not to be the case. I fitted ¾” hose fittings to facilitate large flows if needed, only to realise that the inside diameter of the Gardena fitting is a mere 9mm in diameter so this circumvents all the large diameter pipe I used.

The second reason would be that the distillate passes down a track of perhaps 6mm wide in the tube. So from a volume point of view, the distillate running down the copper tube would pretty much have the same contact area in either tube. While the large tube dies act as a heat sink it also needs to get rid of this heat but due to the thermal mass of the larger tube the rate of heat exchange is less than with a lighter tube. The 22mm tube has 33% more copper mass than the 15mm tube.

So the decision is whether I should simply build a 22/15mm Liebig to replace the existing one. Having said which, there still exists the potential for thermal dead spots even with the smaller condenser. I see there is a nice work around which spirals some medium around the inner tube to create “turbulence”.

I am not sure how effective this spiral is? If the spiral caused the water to flow up and around the inner tube mimicking the spiral then definitely yes. This would require little to no gaps around the spiral.

[jog666]

Have you tried slowing down the water?

[silverbean]

I'm not sure how you are measuring the inefficiency of your Liebig, vapour escaping, distillate exiting hotter or cooling water hotter? You are comparing a boiler and column 4 times bigger but Liebig 3 times the capacity so I would expect some difference in performance.Some use quite slow coolant flow and still knock down large amounts of vapour with the water exiting rather hot although they may be rather long Liebigs.
I haven't noticed much difference with mine when I run it vertical or near horizontal, mine is 600mm long half inch inside 1 inch copper with a recirculating pump at about 6 or 8 litres per minute.
I don't know if I would be concerned about the condensed distillate track, the more important thing would be the vapour speed and contact time inside the condenser. I don't see a problem with output temperature as long as it is not vapour coming out.
If you choose to make a new condenser adding spirals wouldn't hurt, they don't have to be that big its just to stop the water from flowing straight along to even out the cooling to prevent hot spots. Plenty of posts in the build section to look at.
Good luck with your new build. But that's half the fun, building new equipment.

[Swedish Pride]

stick a 10mm pipe up the 22mm one and turn it in to a davies condenser?

[NineInchNails]

It is my understanding that one Liebig should perform the same regardless of the boiler size and/or column size and that it's the power input that matters not the size of the column/pot. It's about surface area within the condenser, water input temp and the flow rate that determines the knockdown power. There are ways to aid in maximizing efficiency like making the water spiral around the inner tube, but I never did that and mine works fine. Perhaps you can twist copper mess and spiral that around the inner tube to try and simulate the same thing. The Liebig has to be sized adequately enough to be able to knock down the amount of input power you will be using.

I like shotgun condensers because that design has much more surface area and knockdown power per foot. In other words a relatively short shotgun condenser can easily have more knockdown power than a long Liebig.

[Royco]

My Liebig is 48" / 1,2 meters and is at 45 degrees. Has spirals in the water path as well as inside the vapour path and works very well.
Input is 3500watts to a 50L urn.
Water is controlled by a ball valve to a small trickle, almost the size of the distillate coming out and I find only the top 300mm of the Liebig is hot.
Now will change to a needle valve to get even less water flow.
Am shortening the condenser slightly so I can run vertical due to space constraints and from what the experts post here it should still work well.

[NZChris]

Heat rises, so the only place hot water will stagnate and lower the efficiency is above the outlet. Putting the outlet at the highest point gets rid of the hottest water in the jacket.

There is little advantage from a spiral unless you want to build a compact Liebig that is undersized for the Watts it's going to have to knock down. They only work really well if there is little or no clearance or the velocity of the flow is high enough, otherwise convection lets the hot water rise through the gap as though the spiral doesn't exist. There is a thread about it if you can find it.

Wire wrapped around the inner will create turbulence, for what it's worth.

[Yummyrum]

It is my understanding that one Liebig should perform the same regardless of the boiler size and/or column size and that it's the power input that matters not the size of the column/pot

Agree

[Setsumi]

try to have the water outlet positioned to face upwards, this will ensure that water must fill the jacket completely. thus surounding the vapour tube. i have found if the outlet is pointing down a big shell does not always fill completely on a pc that is not vertical.

[Windy City]

A very easy fix for this is to put copper mesh VERY loosely in the inner tube.
Please make sure this is loose with no back pressure.
When I ran a liebig this made a night and day difference in performance and cut my water usage by quite a bit.
Hope it helps.

[Sulaiman]

I have a 35/22mm OD... the cooling efficiency appeared worse... 22/15mm OD for the condenser.

My still is all glass and I've noticed with a Leibig condenser:

. air/gas bubbles develop on the cooling water side of the inner tube,
if the water flow is high they get dislodged,
normally they coat quite a large area hence reduce cooling efficiency.

. the bulk of the cooling water flow misses the inner tube and just flows up along the inside of the upper surface.

A 'West condenser' is like a Leibig with a MUCH narrower water path (lower annular cross-sectional area) that forces the water to flow faster, dislodging bubbles and flowing more equally over the inner tube.
Cooling water flow is reportedly less than for a Leibig, for similar cooling power.
(but with a higher outlet water temperature)
So opposite to intuition, it seems that less space for cooling water is better.

Adding an internal spiral sounds good,
but I've no idea how difficult it is in practice.

I doubt that the thermal mass of copper makes much difference compared to the large heat flow in the condenser.
(a dry condenser would heat up rapidly)

[v-child]

https://homedistiller.org/forum/viewtop ... 6#p7584553

My 18" liebig with a finned inner tube works quite well.

[Royco]

Adding an internal spiral sounds good,
but I've no idea how difficult it is in practice.


"An internal spiral" -- if you mean in vapour tube and not water path is very easy to do. Just wrap some 1,5 ~ 2,0 mm copper wire round a 5mm dowel to form a "spring". Stretch it to form a lazy spiral. Works very well

[Deplorable]

Adding an internal spiral sounds good,
but I've no idea how difficult it is in practice.


"An internal spiral" -- if you mean in vapour tube and not water path is very easy to do. Just wrap some 1,5 ~ 2,0 mm copper wire round a 5mm dowel to form a "spring". Stretch it to form a lazy spiral. Works very well

Just remember to rinse it out with water after the run or the pooled alcohol will create copper oxide on the coil and tube. That will come out in your next run. Ask me how I know.

[sambedded]

"An internal spiral" -- if you mean in vapour tube and not water path is very easy to do. Just wrap some 1,5 ~ 2,0 mm copper wire round a 5mm dowel to form a "spring". Stretch it to form a lazy spiral. Works very well

It is not a good idea to restrict the flow of liquid in the inner (vapor) part of the condenser. Faster liquid discharge increase a condenser efficiency.

[Windy City]

I had a roll of copper mesh and I tied a string to one end of the unrolled mesh.
I then fished the string through the liebig from one end through the other.
Pulled the string until I had mesh all the way through and then cut the string.
I had thinned the mesh out so it would not cause any back pressure and was loose in the inner tube of the liebig.
This increased the performance of the liebig tremendously.

[Royco]

"An internal spiral" -- if you mean in vapour tube and not water path is very easy to do. Just wrap some 1,5 ~ 2,0 mm copper wire round a 5mm dowel to form a "spring". Stretch it to form a lazy spiral. Works very well

It is not a good idea to restrict the flow of liquid in the inner (vapor) part of the condenser. Faster liquid discharge increase a condenser efficiency.

sambedded this is the first time I have read a post indicating a copper spiral in the vapour tube may be a bad idea. The coil i wound loosely creates minimal back pressure and the condenser works almost too well as the outer tube is cold after 6 inches of the 4 feet have been passed! I have to turn water flow to a pencil lead trickle to get a longer hot ~ cold graduation.

[zed255]

For what it's worth, I had done a bunch of reading and settled on 3/4" over 1/2" (about 22mm over 15mm equivalent) that had an outer jacket from inlet to outlet length of 36" (~1m). I did include a spiral in the water jacket made of 12ga copper wire for a close fit, with coil spacing of about 1" (25mm) or so. I have no 'turbulator' or any other packing in the inner tube.

I do notice some huffing, in particular when stripping or when running really deep, but it is so incredibly effective I can barely even achieve a gradient in the jacket. I resorted to a pressure reducing regulator so the needle valve had more usable range. To get hot water out and a bit of a gradient on the jacket only takes the barest trickle of water on a spirit run and not too much more even when stripping. I have reduced my water pressure to about 12psi.

I suspect your choice of the 3/4" (22mm) inner tube may result in a channel of vapour up the middle that doesn't get cooled adequately. Even though the larger tube allows longer dwell time in the condenser you may be getting some laminar flow. I'd think as already mentioned that a little copper / SS mesh or some method of inducing turbulence or forcing vapour towards the inner tube wall would likely help.

Also, I don't believe the diameter of the riser on a pot still matter much at all so long as it is not so small as to risk an obstruction with a mash containing solids. The speed of vapour in the riser is of no consequence once it arrives at the condenser.

[Andrew_90]

I suspect your choice of the 3/4" (22mm) inner tube may result in a channel of vapour up the middle that doesn't get cooled adequately. Even though the larger tube allows longer dwell time in the condenser you may be getting some laminar flow. I'd think as already mentioned that a little copper / SS mesh or some method of inducing turbulence or forcing vapour towards the inner tube wall would likely help.

This comment makes a lot of sense for me and would explain my opinion of the larger Liebig being less effective. I will think on this and manner to remove the potential of laminar flow.

[Andrew_90]

It may well be easier to simply make a new smaller Liebig. My experience is that it is often easier to start afresh than to modify.

So what I had done is to draw out a distilling bench on wheels to have my still totally confined to a moveable platform for storing and retrieving at a minutes notice and a minutes setup time. The available space did not allow for a 36"Liebig so I opted for the larger Liebig in the belief that its improved efficiency would allow me to reduce to 605mm (24"). Well all the timber is cut, joints made and I simply need to assemble when I get the time. The distilling bench ain't about to change.

So either I modify the existing Liebig or I get inventive. Perhaps copper mesh up the tube is the easiest.

[NZChris]

If you need a short condenser, look at building a shotgun.

[zed255]

If water supply is not an issue where you are, then a smaller diameter 24" liebig condenser might work. I don't see any reason you couldn't use either a shotgun like NZChris suggests or a dimroth (coil in a shell) for shorter solutions. Get creative, there is no one solution to your problem.

Edit: I don't think adding a removable insert to generate some turbulence / vapour movement would be all that difficult to add to your existing condenser. Not a major modification, just an add-on.

[Andrew_90]

If you need a short condenser, look at building a shotgun.

I know, this may be where it end up. It really messes with my layout and the ergonomics of operation that I have designed the bench for. I have a weakness in that the form will generally take president over function. Clearly distilling is about function over form.

On the shotgun. I have two pieces of 2" tube hanging about, one is 300mm and the other is 500mm. It is exceedingly difficult to obtain shorter lengths of tube in this country. The 2" tube will easily take 4 inner tubes of 15mm, 5 tubes is very crowded and I think there would be insufficient coolant with a 5 tube arrangement. So assuming 4 tubes. I would like to keep the 500mm tube for another project but I suppose making a 300mm shotgun is probably not worth it?

Also in the Liebig everyone appears to be at great pains to prevent dead spots of coolant, is the shotgun not even worse?

Finally, why are the inner tubes left proud of the baffle? Surely it would be better to have protruding tubes levelled with the baffle, specifically on the side closest to the boiler.

[Setsumi]

If you need a short condenser, look at building a shotgun.

I know, this may be where it end up. It really messes with my layout and the ergonomics of operation that I have designed the bench for. I have a weakness in that the form will generally take president over function. Clearly distilling is about function over form.

On the shotgun. I have two pieces of 2" tube hanging about, one is 300mm and the other is 500mm. It is exceedingly difficult to obtain shorter lengths of tube in this country. The 2" tube will easily take 4 inner tubes of 15mm, 5 tubes is very crowded and I think there would be insufficient coolant with a 5 tube arrangement. So assuming 4 tubes. I would like to keep the 500mm tube for another project but I suppose making a 300mm shotgun is probably not worth it?

Also in the Liebig everyone appears to be at great pains to prevent dead spots of coolant, is the shotgun not even worse?

Finally, why are the inner tubes left proud of the baffle? Surely it would be better to have protruding tubes levelled with the baffle, specifically on the side closest to the boiler.

a shotgun will have more dead spot potential at an angle than a liebig. i have a shotgun in 42mm shell with 3 x15mm tubes. it has a cooling area of 450mm, it works on my 4" 5 plate flute, in vertical position... i would not want it shorter, that said as long as my recirculation tank stays cool the shell and product is cool.

[Andrew_90]

So 500mm it is, thanks.

[NZChris]

You don't have to have one only Liebig. If a Liebig is too short, you can add another one, even double back on the first one. My first had a plastic water jacket and doubled back on itself to save room.

Another option is a worm. They take up very little space for the same length of inner as in a Liebig.

[sambedded]

I suspect your choice of the 3/4" (22mm) inner tube may result in a channel of vapour up the middle that doesn't get cooled adequately.

It's not possible with adequate cooling unless your vapor moving with supersonic speed. Vapor occupies aprox 2000 more volume than a liquid. Therefore, when some part of the vapor near the inner wall of the liebeg begins to condense, it immediately creates a significant pressure gradient, and the other part of the vapor begins to be sucked towards the walls.

[Andrew_90]

So keeping with a shotgun for now.

I had a thought, most appear to run the inner pipes parallel to the walls of the outer pipe.

I am sure that one could get a degree of twist if rotational force was applied and held during the soldering process. Would such a twist be beneficial for creating a wanted disruption in the flow pattern?

[Yummyrum]

Funny you should say that andrew .
My very first shotty had the twist in its pipes . Was an accident but i think it was a blessing . At the time I was saddened that I had not got them parallel , but that shotty works a treat . I think the twisted pipes aids water turbulence in the jacket and aids turbulence in the tubes .

I think if you look way way back you will find an HD forum classic made by Mash rookie . It is a twisted shotty in a glass shell . ... a work of viewtopic.php?f=50&t=22305#p6911522

[Andrew_90]

Man that is sexy. I could not get that degree of twist.