Condenser flowrate, and its effect on output.

[Dave]

I've seen this touched on here and there, and was wondering if there is any rule of thumb as to how the flowrate in a liebig affects the output. My newbie logic says just get it cold and the ethanol vapour will condense and run out. But there seems to be more to it than that. Can anyone explain, please?
I was thinking of making up a short extension lead which will incorporate a controller, so that I can adjust the speed of my pump. That is, as seems to be the case, it turns out that there is something to be gained by controlling the flowrate.
So far, in my two runs to date, the condenser water hasn't got the slightest bit warm at all. My reservoir is an 80 litre plastic dustbin, and I can't remember what the flowrate of my pump is, but it keeps everything cold. Oh, and my element is 2kw, and boiler capacity 4 gallons max, so there will be about 3 gallons of wash.
Dave

[Easydrinker]

Dude you are touching on something that I consider relevant, yet peripheral and yet maybe relevant.
My neck has been out here long enough that I no longer care what my peers think of what I say.
I cannot guess the effect, but I believe that the cooling effect upon your condenser will affect the distillation. The cooling effect must "creep" back.
Maybe I am just a crazy?
Maybe I am starting to write my own psyche ticket?
Hot Diggety.


Robert

[Curmudgeon]

I'm reasonably confident that there is no difference in quality of output and that on a closed circuit cooling system such as yours there's no benefit to faster or slower cooling as water cost isn't an issue and difference of power usage would be minimal.

I assume over cooling is better than under in terms of avoiding alcohol escaping without being condensed.

The only argument I can find is to have your alcohol as close as possible to optimal temperature for alcohol hydrometer reading in your parrot.

https://www.google.co.uk/search?hl=en&q=liebig+flow+rate

[Easydrinker]

OP point missed here methinks?

Robert.

[Mash]

Logically I can see no reason why the speed of cooling affects output.... Except when the condenser is not working well enough to condense the volume of vapour being produced.
Then more water would solve the issue and the productivity would go up.

Often wondered if a small S trap at the bottom of the condenser would be a good idea to catch any escaping vapour?

[Easydrinker]

I am suggesting that if you cool the condenser aggressively, without turning up the boiler,then you may get a cool Lynne arm and even swan neck, Result, Reflux, even in a Pot Still.

Robert.

[Curmudgeon]

I am/was thinking along Mash's lines.

I take your point Robert, but was only thinking of sufficient condensation or not on the downward/output side after the highest point and realistically at cooling out so was assuming minimal condensate getting back to top and back to the "input" side ie reflux.

edit : I may mean vapour rather than condensate, if there's a difference.

[Easydrinker]

I may have this wrong, but condensate is condensed vapour.

It would be possible, in my Very Silly Still to turn this back to vapour, purely due to the very long lengths of pipe, and two cooling sources.
Condensing it again would be more of a challenge.
But then, It is a very Silly Still, and outwith what most folk use.
It keeps me off the streets.

Robert.

[Curmudgeon]

I think we're discussing the difference between after compared to before the lyme arm/peak of the column. After is output temperature and speed and before is potential reflux?

[Myles]

I am suggesting that if you cool the condenser aggressively, without turning up the boiler,then you may get a cool Lynne arm and even swan neck, Result, Reflux, even in a Pot Still.

Robert.

Robert is absolutely correct on this point and I have seen it in practice. With a big liebig too close to the riser on a pot still you can actually get zero output as a cold zone extends into the top of the riser.

I had to put in an extra section of tube to get the liebig further away from the riser.

On the issue of degree of cooling of the product the most important thing is that the vapour is all condensed. It can be convenient to cool it to the correct temperature for your hydrometer if you use one. However it also makes sense to have it warm as this aids airing. That is just your personal choice.