How to centering reflux?

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TheMechwarrior
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How to centering reflux?

Post by TheMechwarrior »

I see a lot of talk about condensate running down the column and the need to center the flow to within the vapour path for best results.

I'm interested in hearing about successful methods people have used, particularly pictures.
I've heard of people using a concentric reducer welded to the inside of the pipe, is this the most common method?

Cheers,

Mech
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kiwistiller
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Re: How to centering reflux?

Post by kiwistiller »

Mine aren't welded (well, the one at the top of the column is, and I wish it wasn't). Just a filed down reducer will do, wrap a tiny bit of mesh around it and it will stick when you put it in the column. I'll flip you a pic when I go out to the shed.
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kiwistiller
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Re: How to centering reflux?

Post by kiwistiller »

reducer
reducer
scrap o' packing
scrap o' packing
sticks in there just fine.
sticks in there just fine.
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myles
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Re: How to centering reflux?

Post by myles »

I use the cut down reducers inside a slip connector or T.

Image

Image

There is still enough space in the connector to fit the next section of column.
A reduced branch T makes a good thermometer port, and can be combined with a centering funnel.

Image

Image
kiwistiller
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Re: How to centering reflux?

Post by kiwistiller »

something else for your consideration... I use this to shove the reflux to the other side of my VM column from my takeoff port (it's centered again below takeoff), took all of a pair of kitchen scissors and 5 minutes to make. I was getting splashing problems. doubles by reducing the vapour path to my condenser, giving me more control with my valve... but I digress....
side
side
bottom
bottom
Using similar construction you should be able to come up with a centering ring-ish thing if you have a bit of old sheet lying around.

Smarter people than me have claimed that it isn't so much the ring or whatever that is important, but the restriction (in absence of packing). The goal of centering is to break up large 'clumps' or 'streams' or 'channels' of reflux that occur as surface tension rises (ABV dropping) and redistribute it more evenly. In a centering solution, you boost up the vapour speed in a localised area, to a limit of around 100" per second (after that, it'll choke / flood / ruin your day). That speed is said to be enough to pretty much blow any channels into smithereens. Of course, sensible design is still needed, like not having the bottom of the ring angling back towards the walls or anything like that, but it shouldn't be critical to have a smooth ring.

That being said, mine are obviously smooth, so take the above idea as 'theory', not tried and true.

I've seen others hammer sheet or flattened pipe into a dish shape and drill the center of it.

Remember, you need at least 1" in a 2" column (smaller than that, and it'll choke / flood / ruin your day :D )

[posting same time as myles]
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