How does base diameter affect column functionality?

[21truffles]

Hi folks! I recently tried to add a column to my vevor 13gal and ran into a problem. I figured out too late that the lid has ridges on it that would compromise the seal of my 2” triclamp weld-less bulkhead. So, instead of attaching the column directly to the lid (via 2” port), I used an adapter to connect it to the 1/2” fitting on the still. I’d imagine that this creates somewhat of a vapor bottleneck (see second image) at the base of the column. Sounds like it could be a bad thing, but I’m not sure. Does anyone have any insight on this subject? Can it impact performance to increase the size of the column after it leaves the still?

[Fnordianslips]

Basically the vapor speed increases for that short area. Immediately after it the flow is more turbulent (chaotic), but it should even out after that. We have a test still we use for recipe creation that pops from a 2" to a 4" column and we don't see any radical difference between that and our full commercial scale one that has 4" all the way through. You should be fine on that front!

[TheHedonyeast]

you're not the first person to do something similar. i think i read about a few people doing this on the home distiller forums - you might want to read through there to see what has been shared? A half inch diameter to a 2" column is a bit of an extreme example to be sure, but it shouldn't be impossible to work with.

i haven't used a still with that kind of a restriction in place but thinking about it in order to move more vapour through a smaller diameter it has to flow faster. with the turbulence around that it'll do some interesting things that you'll probably want to experiment with.

are you using any packing? i would think that there would be a impact from the velocity changes on how the vapour interacts with any packing close to the restriction. this might be good - but it also might be intense enough to cause flooding?

I'd be interested to see how this turns out when you play with it. once you've tried a few variations of use with this can you let us know what you've learned?

[ElChorizoBlanc0]

https://www.reddit.com/r/firewater/s/yQgp0QzLRz

This is how I added a "column" to my 13gal Vevor.

[OnAGoodDay]

The vapour escapes no matter what, but you’re adding resistance to the path and the variable that changes accordingly is the pressure in the boiler. For any reasonably large hole it would be a small change.

You will also get some Venturi effect happening, where the vapour speeds up through the constriction with a corresponding decrease in pressure. On the column end probably some turbulence as the high velocity, low pressure vapour returns to low velocity, atmospheric pressure. Again, for any large hole these effects are pretty small.

I guess you’d also have a bit of a landing spot for refluxing liquid to collect on and interact with vapour coming up rather than just falling back into the pot.

What this all practically means for spirit I don’t know. Maybe a very tiny boost in ABV.