Liebig pipe diameters

[Easydrinker]

Wild cat slunk into "crush cage" tonight to hunker down after feeding.
All is gonna be sweet.
Will speak to vet on the morrow.
Some of you softies might be interested.

Robert.

[Mash]

Don't know what you mean

Nice one.

[Dave]

Same goes for the inner pipes that are crushed alternating by 90degress each time on the foolish premise that ‘it exposes a greater surface area to the water’ ..... pfft!

Crimping the inner pipe is not to increase the cooling effect that the water has, what it does, or is supposed to do is induce turbulance of the vapour, so that more, or all the vapour reaches the cool outer wall of the inner pipe. This reduces, or eliminates the chances of a hot core of the vapour from never touching the cooling suface and exiting the pipe still in vapour form. But as Myles points out, if the the condenser is too far off the vertical, it can lead to pooling. But my own thoughts are that if you tip the condenser at the end of the run, any pooled distilate still left in there will just run out.

[Easydrinker]

The problem with "pooling" is not recovering the distillate that gathers, but the possible smearing between cuts caused by it.

Robert.

[H12rpo]

Hmmm ‘hot core of vapour’ ......I don’t believe that exists. Hot vapour rises so if there is any difference in temp of the vapour that is flowing through the condenser, then science would dictate that the hottest part would always be at the uppermost. Crimping the pipe would not expose more hot vapour to the cool jacket even if it’s crimped and anyway even if it did so what? All you would achieve is a marginally shorter condenser....what’s the point of that?
Load of nonesense is my view, sorry.

[Dave]

Fair enough.

[Myles]

Hmmm ‘hot core of vapour’ ......I don’t believe that exists. Hot vapour rises so if there is any difference in temp of the vapour that is flowing through the condenser, then science would dictate that the hottest part would always be at the uppermost. Crimping the pipe would not expose more hot vapour to the cool jacket even if it’s crimped and anyway even if it did so what? All you would achieve is a marginally shorter condenser....what’s the point of that?
Load of nonesense is my view, sorry.

@H12rpo there are two flaws in this argument.

I was sceptical at first, but it has been demonstrated that even a vertical reflux condenser (open to atmosphere at the top) works when the hot vapour is introduced in the top 1/3 of the condenser. WHY? because as soon as the vapour enters the cold zone it immediately contracts, increasing in density and starts to fall.

On a product condenser there is another point. It is not open at the top. The hot vapour does not get the chance to rise - IT IS PUSHED.

There is no time to set up a temperature gradient in the product condenser - it is a forced situation - imposed by the coolant. Turn off the coolant and you get hot vapour being forced out of the product condenser. Without cooling that PC is just a short length of tube.

As for the point there are two. Reduce the length of the condenser or reduce the amount of coolant used. It makes a big difference if you are using 5 kW or more.

Now I personally do not like crimped inners - the smearing issue as mentioned previously - but I know they work. So does adding turbulators inside the vapour tubes.

I prefer to reduce the diameter of the vapour tube to 12 mm. It increases the total cold surface area inside the condenser and reduces the maximum distance between vapour and a cold surface to 6 mm. On my coiled liebig I went down to 10 mm tubes.

However, all of this is just personal choice. There are lots of condenser designs - you just use the one that you want to use.

[H12rpo]

My ‘science’ about the vapour being hotter at the top than the bottom is based on the Liebig being at an angle ....say 45 degrees rather than vertical. Albeit I accept that it would be a minuscule difference in temp.......I think that’s my point, there wouldnt be any noticeable or measurable difference.
My initial point is still valid.....crimping the inner vapour tube does not expose the vapour to any more of the surface area of copper exposed to the coolant jacket. It simply isn’t possible.

[Myles]

H12rpo there is a big error in your last statement. There is a MASSIVE temperature difference. If there was not then you would have hot vapour spewing out of your condenser.



Crimping does two things. It interrupts the laminar vapour flow. Each bump introduces turbulence in the vapour close to the wall. In big diameter condensers this laminar flow is a real problem. Only the vapour closest to the cold wall actually condenses. It is why they put in spiral wire turbulators - to break up the laminar flow.

Crimping the tubes also actually stretches the copper. It is the same reason that farmers plough grass paddocks into corrugations. It increases the surface area so they can grow more grass.

[H12rpo]

It doesn’t matter that only the vapour near the pipe wall condenses. if there’s no vapour that comes out trend of the tube then it’s done it’s job. As some of the vapour condenses (the outer sheath if you like) then an inch further down the pipe there is no more outer and what is the inner then becomes the new outer sheath which condenses and so on until there is no inner left.

I don’t accept that simply crimping ‘stretches’ the tube by any measurable amount and thereby increases the length of cold pipe exposed, and like I said even if it did, so what? It’s not needed. I don’t have any crimps and there’s no vapour which comes out of the end of mine.
The grass growing analogy is not really comparing apples with apples......I can see that mini hills and vales actually increase the surface area there.

I don’t get any lamina flow problems in my condenser, though it may be that there are some in very big jobbies where the vapour just shoots through with not enough cooling wall to knock down.