My new Liebig.

Anything cooling/condenser related.

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Ignor the ignorant
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Re: My new Liebig.

Post by Ignor the ignorant »

I'm working more on the theory of flat plate heat exchangers, lets say that most of the vapour is knocked down in the first 2/3rd's of the 15mm covered by the coolant jacket leaving the remaining third as carrying mostly hot product. The cold coolant at the jacket inlet will have a harder job cooling down a concentrated stream of hot fluid contained at the bottom of a cylinder than it will as a broad film of fluid over a flat plate.
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Re: My new Liebig.

Post by squeezins »

I took a flat piece of copper and twisted it like a long flat screw and put it in one end and did the same thing on the other end except going in the opposite direction . The thinking was to create a spiral path keeping the vapor in contact with the cool copper longer by slowing it down and adding surface area. It allowed me to do stripping runs at a much faster rate.
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Re: My new Liebig.

Post by rad14701 »

Ignor the ignorant wrote:My reckoning is that by flattening (sqashing/ making into a rectangle etc) of the fluid tube inside the water jacket to allow more of the condensate to come into contact with the copper must make the cooling of the liebeg more efficient.
We just had this very same discussion about a week or so ago... Don't confuse vapor with liquid... With vapor, as it starts to collapse (condense) it will draw the rest of the vapor along with it... This is entirely different from the physics surrounding liquid which can have the center-most portion act as an insulator against cooling... Just keep reminding yourself that vapor collapse is more efficient because there is nothing to impede heat from being attracted to cold...
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Re: My new Liebig.

Post by jacklance »

As an experiment, I want to try to ferment and distill a small amount of ethanol. What ratio should I use the sugar and the yeast? How long will it take? What apparatus is required? (I have a liebig condenser etc) How pure can I get it?
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Re: My new Liebig.

Post by Samohon »

jacklance wrote:As an experiment, I want to try to ferment and distill a small amount of ethanol. What ratio should I use the sugar and the yeast? How long will it take? What apparatus is required? (I have a liebig condenser etc) How pure can I get it?
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Re: My new Liebig.

Post by Ignor the ignorant »

rad14701 wrote: We just had this very same discussion about a week or so ago... Don't confuse vapor with liquid... With vapor, as it starts to collapse (condense) it will draw the rest of the vapor along with it... This is entirely different from the physics surrounding liquid which can have the center-most portion act as an insulator against cooling... Just keep reminding yourself that vapor collapse is more efficient because there is nothing to impede heat from being attracted to cold...
Seems that your treating the liebeg as purely a condenser, when surely it can be a cooler as well ( as sometimes seen on the output tube of a Bok ).

Anywhoo, i went ahead & squashed the fluid tube ( 15mm ) with a pair of pipe grips mostly, this left a cross section of tube within the 2'6"jacket of approx 8mmx17mm. Length of inner squashing was around 20" & i certainly wasn't interested in making it real smooth, just as long as the flats were top & bottom.

How did it perform ? --- well i really can't complain, the Sam based pot still ,23l boiler with a 3kw element on continuous will produce 3litres+ /hr of distilled water at a temp of 25C, flow rate of approx 2 l/m i think.

For product it still did the 3l/hr exit temp 22c at 0.5 l/min, cooling input temp 10c cooling output temp 55c

Is this performance any different to what i would have experienced by using a standard piece of tube i don't know but to dismiss it without giving it a go would always be nagging at me.
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Re: My new Liebig.

Post by gonagin58 »

That's a pretty good idea, think I'll try that. Thanks.
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Re: My new Liebig.

Post by myles »

These "bulbed" vapour tubes with the constrictions, are quite good at increasing the turbulence in the coolant which is a good thing. However, you do need to remember that these really have to be mounted vertically. In any other position there is a tendency to get condensate pooling in each bulb. That is not a good idea.
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Re: My new Liebig.

Post by Superbigstevie »

I can not find any information on how long, what size a liebig needs to be. I am overwhelmed by all the variables. I was thinking about a 3/4 inside a 1" for my 15 gallon pot. Would 24" long get the job done? I can not afford to build twice. Thanks in advance for the help/ideas.
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Re: My new Liebig.

Post by rad14701 »

Superbigstevie wrote:I can not find any information on how long, what size a liebig needs to be. I am overwhelmed by all the variables. I was thinking about a 3/4 inside a 1" for my 15 gallon pot. Would 24" long get the job done? I can not afford to build twice. Thanks in advance for the help/ideas.
24" sounds rather short... There are calculators on the parent site to help make informed decisions... I'd go with 36" - 42" for liebig length... Better too much than not enough cooling...
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Re: My new Liebig.

Post by GuyFawkes »

Just as a word of advice to anyone trying this who is like me..... I am about the polar opposite of an electrician, so forgive me in advance for butchering the terminology here:

I had some bare copper wire for grounding, the style that is smaller wires twisted together. It was pretty soft and pliable so I figured it work well to use in my new liebig in the method hookline describes. So I try to attach it and find I can't even begin to find any method to actually attach it. Maybe I just suck too much at soldering, maybe I was just unlucky, who knows.

I was frustrated and almost gave up before I remembered my wife had bought some stiff bare copper wire (like 12-14 gauge, I would guess) that was one solid piece of copper rather than smaller twisted strands. I twisted this around the liebig and it was MUCH easier. No soldering necessary, it held itself on just fine and could be slid into the top tee connection and then just slide the bottom tee onto it and it's locked into place.

Maybe this was suggested elsewhere in the thread and I missed it (or maybe it's self explanatory), but if there is anyone else like me reading this, hopefully it's helpful!
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Re: My new Liebig.

Post by TOAD »

Copper ground wire as you describe is just how i made my condenser. I found that a hose clamp holding yer starting point in place helps greatly. I actually prefer the multi strand wire over the single piece (im not an electrician eather but you know what im talking about) it seemed to "suck up" the sodder' alot better and it has some give to it when you sleeve it with the outer jacket.

On a side note: Liebig angle. I cant understand a straight up and down one. Even at a 45• angle. It seems to me that the recently condenced likker would roll down hill fast as it could, exchanging little heat as it went. Seems to me that a condenser set just slightly off level (low side at the collection end obviously) would allow the condensate to flow over the cooled copper slower and therefore, more efficiently. This is just in theory, and work scedual wont allow me to test this, but would a more "shallow" liebig be more efficient than a "steep" one?
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Re: My new Liebig.

Post by GuyFawkes »

I think the idea behind it being vertical, and anyone jump in to correct me if I'm mistaken, is primarily because it helps prevent "pooling" of the condensate within the liebig, especially when using scrubbers or a coiled wire within the liebig itself. Pooling could muddy up your cuts and potentially decrease efficiency.

Also, I used the "solid" wire because soldering it was not necessary. I just wound it tight around the liebig and it held itself on rather well. I imagine to some degree allowing the coolant water to flow around the wire in between it and the pipe could increase turbulence and efficiency as well. Obviously no data to back that up though.
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Re: My new Liebig.

Post by myles »

IIRC the arguments around liebig angle with regards to efficiency, are based on a consideration of water usage. In other words a vertical liebig uses less water to knock down vapour than an angled one. I suspect this is also related to the cooling effect mentioned previously, although I have not seen it specifically mentioned.

It makes sense though. An angled liebig is going to cool the product more than a vertical one, as the condensate is in contact with a cold surface for longer. This off course means the coolant absorbs more energy so in terms of water use it is less efficient as you would need to use more water.

For our purposes though it probably is not a big deal. I tend to use liebig angle just as a matter of convenience to suit the collection point. It is worth reminding folks though that some of the designs are constrained to a vertical orientation for practical reasons due to condensate pooling.

My coiled liebig for example, HAS to be mounted vertically or it will develop vapour lock problems. Straight multi core liebig / shotguns can be mounted at an angle if you wish, but a spiraled or coiled graham style would have problems on an angle. It is worth thinking about before you start building though.
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Re: My new Liebig.

Post by crazyk78 »

Ok I've read through a large number of posts on what dia tube to use.

The two main ones are as used by Hook in the original post.

So here in Aus I'm finding it very difficult to find Ts to suit 3/4" inner 1" outer so how are your 1/2" inner 3/4" outer liebigs performing?

Who's using the smaller one without the internal spiral in the water jacket, does it perform adequately?
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Re: My new Liebig.

Post by emptyglass »

crazyk78 wrote:Ok I've read through a large number of posts on what dia tube to use.

The two main ones are as used by Hook in the original post.

So here in Aus I'm finding it very difficult to find Ts to suit 3/4" inner 1" outer so how are your 1/2" inner 3/4" outer liebigs performing?

Who's using the smaller one without the internal spiral in the water jacket, does it perform adequately?
I make em quite often. 1/2" inner with 3/4" outer. Wire wrapped inner is a real good efficiency gain. I cant tell you the exact % of efficiency gain with a hookline spiral, but its in the order of 10 to 15%.
You need to stop to stop laminar flow. Big efficiency killer.
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Re: My new Liebig.

Post by crazyk78 »

So I ended up making my 1/2 , 3/4 with only a small half round spiral in the centre of the tube. All I can say is this thing knocks down all vapour and the distillate comes out nice and cold.

Thanks ppl
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Re: My new Liebig.

Post by frodo »

ya'll are hurten my head with this mm measurments, i am a plumber, we call 1/2" copper 1/2" id, copper
it actually is 5/8" od but we go by the id size
3/4 is 3/4 id or 7/8 od
use the id or the od terminoligy and then you can be understood by plumbers, ac tech,

ac tubing is [ line sets to your condenser] is od sizes
''little tricks emerge here....3/4 od fits into 3/4 id and can be used as a transisation between the two...



like your liebig, nice work, good solider job also,,, you wiped your joint..thats a A+ in my book for craftsman ship
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Re: My new Liebig.

Post by frodo »

TOAD wrote:Copper ground wire as you describe is just how i made my condenser. I found that a hose clamp holding yer starting point in place helps greatly. I actually prefer the multi strand wire over the single piece (im not an electrician eather but you know what im talking about) it seemed to "suck up" the sodder' alot better and it has some give to it when you sleeve it with the outer jacket.

On a side note: Liebig angle. I cant understand a straight up and down one. Even at a 45• angle. It seems to me that the recently condenced likker would roll down hill fast as it could, exchanging little heat as it went. Seems to me that a condenser set just slightly off level (low side at the collection end obviously) would allow the condensate to flow over the cooled copper slower and therefore, more efficiently. This is just in theory, and work scedual wont allow me to test this, but would a more "shallow" liebig be more efficient than a "steep" one?
the solider being sucked up is due to http://en.wikipedia.org/wiki/Capillary_action

when you solider, first heat the whole fitting, then move your flame to one side,in the back of the fitting,,and touch the opsite side with the solider, solider will "run" to the heat..
are you neutralising the flux with a baking soda wash before putting the 1/2" copper into the 3/4" sleeve?
flux is acid based it cleans by eatting the outter layer....if not neutralised it keeps on eatting
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Re: My new Liebig.

Post by harry houtin »

Some vary good designs, and tests, it sure got me thinking that I should add spirles. I have a 1/2" inside 1" copper no spirels guess I will take it apart and add spirels inside coolent pipe out side of 1/2" copper. see how this works then maybe add copper wire to inside of vapor tube. winde wire on mandrel just slide it in there solder at outlet end. if it don't work all I have to do is unsolder and pull it out

thanks for all the info
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Re: My new Liebig.

Post by engunear »

This is an old thread and maybe all have lost interest.

Can someone explain to me what is meant by this word "efficiency" in this context?

It seems that this is a case of conservation of energy. We have a heat input (power) and heat output (coolant). We can lose heat if the system is not properly insulated. So lets assume its well wrapped and all.

The equation snuffy has is

Power = flow rate * temp rise / specific heat of water

So where does efficiency fit? As long as no vapour is emerging from the leibig, why does it matter how long it is? Hookline's measurements seem to violate basic physics. (Not being critical of Hookline, its really hard to make good measurements. I made a mistake when I was in high school so I know what it feels like ;-) )

Yep, I can see how turbulent coolant would allow a leibig to be shorter for the same heat input and water input (someone commented on that), but what is "efficiency"?
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Re: My new Liebig.

Post by yakattack »

If I understand correctly, efficiency comes into play in the amount of water you need to pump through it in order to maintain proper cooling and temp gradient.

The longer the condensor the less water flow needed as it allows it to be knocked down over the distance. A shorter condensor will require more water flow to achieve the same condensing power.

By adding in the wire (disturbance) you force the water to take a longer path through the condensor. Thus simulating a longer condensor, which allows you to slow the water down and ultimately use less. As this particular condensor was ment to be run from a tap so he wanted to reduce the amount of water used and shorten the condensor itself.

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Re: My new Liebig.

Post by DAD300 »

Throw in the idea of turbulence there. The greatest efficiency comes from making/forcing the max amount of vapor to contact the max amount of cooling surface. The vapor needs turbulence in the inner space as well as the coolant in the jacket.

You can have a three foot long inner surface, but if the vapor can fall through the center...some of it will.
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Re: My new Liebig.

Post by rad14701 »

As mentioned, "efficiency" is removing the most heat with the lowest possible coolant flow rate, whether recirculating or wasting... I have the copper wire wound between the inner and outer tubes and would like to try inserting a twisted copper ribbon up inside the 1/2" vapor tube... I already utilize a tuft of scrubber to help eliminate huffing and surging due to over-cooling induced premature vapor collapse... My hope is that the twisted ribbon "turbulator" will eliminate the need for the scrubber...
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Re: My new Liebig.

Post by Jacksonbrown »

You can change the efficiency with different flow rates but to work it out it actually has nothing to do with flow rates.
It is more to do with how close can you get the outlet temp to the vapour temp.
Lowering the flow rate helps out by increasing the residence time.
Basically this means you can change the efficiency of you condenser depending on how you choose to run it.

See here

η% = 100*(t2 - t1) / (t3 - t1)

where

η% = temperature transfer efficiency

t1 = inlet temperature

t2 = outlet temperature

t3 = vapour temperature
So a PC that's on a neutral run (78° vapour temp) using 20° cooling water with an outlet temp of 60° has a transfer efficiency of about 69% from the vapour side to the water side.
You can't possibly get the outlet temp higher than the vapour temp as that would be more than 100% efficiency.
(I'm pretty sure that's right :D)
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Re: My new Liebig.

Post by HookLine »

Can someone explain to me what is meant by this word "efficiency" in this context?
Minimising condenser size for given quantity of heat exchange.
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Re: My new Liebig.

Post by Jacksonbrown »

That's kinda the opposite.

To have the smallest possible condenser i.e. the smallest surface area, first start with a material that conducts heat the best, copper.
Then you need the largest possible difference in temperature (deltaT) from coolant to vapour. Start with a really cold feed and have a really high flow rate so the output is also cold (small gradient).

That would give you the smallest condenser to perform a given duty but plug those number is the equation I put up it would be the least efficient.
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Re: My new Liebig.

Post by still_stirrin »

Ideal efficiency is when the heat removed equals the heat introduced, or more appropriately the heat (flow) in the vapors is transfered to the coolant. This is examplified by Jacksonbrown's quote:
Jacksonbrown wrote:
η% = 100*(t2 - t1) / (t3 - t1)

where

η% = temperature transfer efficiency

t1 = inlet temperature (coolant)

t2 = outlet temperature (coolant)

t3 = vapour temperature
You can see, that as the t2 approaches t3, that the term (t2-t1)/(t3-t1) approaches unity (1). Therefore, the efficiency of the heat exchanger approaches 100% (ideal HEX). Note - in this equation, we're assuming the product outlet temperature is equal to the water inlet temperature.

In reality, some heat is lost to convection from the shell jacket. And some heat is generated inside due to friction. But balancing the flow rates (mass flow) such that the outlet water temperature approaches the vapor inlet temperature and the product outlet temperature equals the water inlet temperature would be the best operational design.

If there is a great difference between the water inlet temperature and the vapor inlet temperature, it may require more contact surface area to conduct the heat all out so that the product outlet temperature approaches the water inlet temperature. Again, approaching ideal heat transfer.

And turbulation improves the convective heat transfer within the respective fluid tubes so that the vapor tube can conduct the heat from one fluid to the other along that path (vapor to coolant).

In reality, the efficiency equation includes the mass flow rate and heat capacity of each of the fluids when multiplied by the temperature differences, and for the vapor that would include the heat liberated during the change of phase as well.

As a note, a properly designed shell and tube HEX can be physically shorter than the conventional concentric tube in tube because of the increase in conducting surface area between the vapors and the coolant. Likewise, the coolant flow rate can be reduced compared to the tube in tube HEX....more efficient, right?

Good design discussion gents. Mech engineers have studied this as a course (of course). But others can benefit from the practical knowledge shared. Thanks all
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Re: My new Liebig.

Post by HookLine »

Jacksonbrown wrote:That's kinda the opposite.
Maybe I should have said the aim was to reduce size (or increase HEX for a given size), not to minimise it absolutely.

Wasn't chasing a theoretical ideal, just trying to increase HEX capacity for a simple Liebig to help keep its size down for hobbyists, using simple design modifications to increase coolant turbulence and extend the coolant pathway (i.e. increase coolant contact with the HEX surface), taking into account practical factors, (not too complicated, able to handle up to about 5000w with room temp coolant, and using off-the-shelf materials and simple construction techniques that most of us have ready access to).

Liebigs don't take up much volume, but they have a large linear dimension (length). If we want to minimise linear dimensions we could do a lot better than a Liebig, particularly as it is not the most efficient design to start with. A multi plate condenser, or a multi-tube-and-shell would do it. But both those have a substantial construction component. Dimroth coils in the thinnest walled copper tube practically possible would also do the job, if you can wind them. They are very efficient, if you control vapour flow around them so as to force it onto the HEX surface. Maybe also using a cold finger in the centre

But otherwise, point taken. 8)
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Re: My new Liebig.

Post by Bagasso »

HookLine wrote:
Jacksonbrown wrote:That's kinda the opposite.
Maybe I should have said the aim was...
That's really it. Efficiancy can apply to different things. Thermal exchange efficiency is what Jacksonbrown was talking about but there is also efficient use of materials, time and space.

What happens when you have a swimming pool to use as a reservoir but a small shed to work in? Well then thermal exchange efficiency isn't that important and a small "inefficient" condensor that let's you get other things done while the still drips in a corner is more efficient space wise.
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