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Vapor Path/Flow and the effects of Product Condenser

Having not really studied the vapor/flow collapse theories I see posted every now and then, I just got a surprise. I read those theories as the Product Condenser providing a vacuum effect as the vapor became liquid. So, I believed, a small diameter PC wouldn't effect the vapor or product flow.

My usual condenser is a triple wall Liebig, or as I now think of it, it is a Liebig with a Dimroth up the center.


From the standpoint of vapor flow, I have a 3" VM with a 3" takeoff, and (with the above PC) it narrows into a 1/2" vapor path in the Product Condenser.

For an early Xmas present, I bought myself an SD 2" x 20" seven tube shotgun. Pure vanity, I thought...they are pretty! Although I had hoped for a reduced water flow.


Well, I got the reduced water flow as I expected, +10%...and product comes off about five degrees F cooler.

What I didn't expect was a faster takeoff...I can only assume that the Shotguns seven ~3/8ths tubes took some pressure out of the system vs the old PC's one 1/2" vapor path.

Very nice surprise...

I think the PC is the most overlooked part of most of our rigs.

I will always preach that you need to oversize or properly size your Product Condenser while designing your setup!

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DAD... not yours.. ah, hell... I don't know...


  • Here, here! I just upgraded to the 3" long PC myself. Cleaning run happens tomorrow.

  • Scrub it good...those tubes have waxy polishing compound in them.

    DAD... not yours.. ah, hell... I don't know...

  • Do you think a vinegar run would take care of it?

  • Provided there is no restriction in the vapour path before the condenser, the pressure/vapour speed reduction is not unexpected. Just based on the tube dimensions the total cross sectional area of the new condenser is significantly bigger than the old one.

    I always say to match the condenser to the power input, and keep the vapour speed as low as is practical in the condenser. Higher speed means you need a longer condenser to compensate for the residence time.

  • @Mtnmann said: Do you think a vinegar run would take care of it?

    I'm not sure @Mtnmann, Punkin alerted me today that there was a complaint about the waxy polishing compound (not sure but I don't think it was @dad) and I'm also not sure of the best way to remove it.

    It took physical scrubbing for me to get it out of my surge breaker, and I'd ran that part in my system many times but the problem area was not directly in the path of the distillate. If I had a rifle cleaning brush I'd use it. If I can find the right size rope I recon I could tie knots every inch or so and use that to scrub out the pipes?

    Tan is talking with the factory to see if there is a step they can take to avoid this in the future.

  • @dad, thanks for the excellent write up. Now you have me thinking I'll need to test the 2" long PC and then a 3" PC when my 5" Crystal Dragon comes together just to see it the takeoff rate increases :-??

  • edited January 2014

    @Myles said: I always say to match the condenser to the power input, and keep the vapour speed as low as is practical in the condenser. Higher speed means you need a longer condenser to compensate for the residence time.

    Higher speed means you need a longer condenser to compensate for the residence time. I'm not sure that physics supports that? There's a lot of things at play but if any thing very high speeds mean turbulent flow and _better _contact with the condenser. A PC would have distillate and vapor going in the same direction so not flooding in the tubes. The cooled vapor condenses and the void is instantly taken up by more vapor unless you've oversize in which case your just cooling air.

  • I removed mine with fores and a 12ga shotgun bore cleaner. Came out easily and now I have a shiny set of tubes :)

  • I ended up using a .223 chamber brush, worked like a charm. Just a heads up, I did notice that on the inside of the holes drilled into the surge breaker there were flaps of steel still connected and covered in the waxy substance. I took a dental pick and was able to wiggle them till they snapped off. It appears that they are drilling the holes after welding in the liquid "hood" and then they aren't able to properly de-burr and clean up in there. After my little touch ups, everything is clean and working quite well.

  • No complaint, the thing is beautifully polished. I have been more than happy with your products and delivery.

    I expected the reduced water usage.

    And while I didn't expect it, I am surly happy with the increased takeoff.

    DAD... not yours.. ah, hell... I don't know...

  • Tie a string to a rag and pull through. Prolly would not hurt to dampen the rag with some kind of solvent......Not sure what kind of solvent would work best? :D

    StillDragon North America - Your StillDragon® Distributor for North America

  • edited January 2014

    @dad, My initial assumption about increased yield would be that an under sized condenser would cause a portion of the vapour to pass straight through the tube and not be condensed.

    I had a similar issue on my old set up using a burner and a homemade copper liebig. The solution was copper mesh inserted up the tube to increases contact with the vapour and create a bit more turbulence in there.

    You may have also had a vapour leak that has since been rectified. Both are potently dangerous and wasteful situations.

    Mass flow through the part should not be affected.

    Added insulation would also cause less internal reflux and allow more of your heat input to make it through your condenser

    The tubes in my new shotguns also need a good clean. I have them in CLR at the moment but if they need it I’ll run a brush through them. I’m guessing they’re ½” tube, 1.6 wall? 9.5mm hole? A .375 cal bore brush would be about right if those number are correct. I have some Autosol at home would this be OK. I don’t use JB bore paste but that might be another option.

  • @dad said: What I didn't expect was a faster takeoff...

    @jacksonbrown, HMMM yield is a completely different thing... his yield may have remained constant..

  • @dad, don't get me wrong, unless someone alerts us about a QC problem we don't react so it's best for everyone, especially StillDragon, when someone sounds the alarm.
    In the beginning, the factory had several different people responsible for testing the condensers for leaks after they were polished. But a few leakers got through!
    Since then they have only one person that is totally responsible to test each condenser (SD buys a LOT of condensers) and so far that has worked very well.

  • OK so total yield is unaffected?

    Looking at the photo, is it a vapor ‘management’ with a 50:50 split in the vapor path? No baffles or valving? How is the reflux ratio controlled?

  • daddad
    edited January 2014

    @Lloyd, seriously no complaint. I'd have washed the condenser just like any other piece of new equipment. Anything that beautiful...I want it to be dirty...

    @jacksonbrown, the previous condenser was a triple wall Liebig. There are no leaks and my yield was constant, but about 12 percent faster. And faster is good.

    The still is a Condenser Controlled VM. I move the reflux condenser down and up the column to block or unblock the takeoff branch.

    image image image

    The reflux coil will and does completely close the take off for 100% reflux.

    This is a variation of what I saw first as a condenser controlled LM.

    The column makes 95% easily, so I only move the coil once during a distillation. The coil never gets over about 120 deg F. So, I can move it with my bare hands.

    StillDragon sells all the parts to make this configuration, except maybe the reflux coil.

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    DAD... not yours.. ah, hell... I don't know...

  • edited January 2014

    @dad, thanks for the photos. It looks like a nice rig.

    How do you measure or know your reflux ratio with that setup? I think you may have decreased your reflux ratio by opening up product vapor path more. A restriction in that line will still act like a VM still if you put you reflux condenser in the ‘old’ positions. Changes in water temp/plumbing could do the same thing.

  • Wow @dad, I've seen the same idea before but never so beautifully executed.
    Love the flexible finned SS tubing!

  • @Lloyd, @dad has been working with the SS tubing since i started distilling... I got the idea to use it in my still from his posts long ago.. and yes he does a beautiful job with it...

  • daddad
    edited January 2014

    @jacksonbrown, how do you know your reflux ratio with an LM?

    If there is no product coming out, I am at 100% reflux. As I raise the coil, I adjust for the flow rate that keeps the ABV at 95% or the desired ABV. The adjustments are instantaneous. After the first run or two I knew the sweet spot...

    I've made this in 2" and 3", with diff size takeoffs and they preform fantastic.

    Yes, as I raise the reflux condenser I reduce the reflux ratio.

    The reflux condenser is so capable that changes in temp do not effect the long as I keep the coolant outflow temp below 140 deg F, the coils knocks down all vapor.

    @Lloyd, the gas industry has gone to coating the SS Flex pipe with yellow plastic making the clean pipe harder to find. Hint...Hint...


    The scrubbie at the top keeps bugs

    Every time I see a tutorial on people continuing to wind copper coils, I cry. The SS corrugated pipe is cheaper than copper pipe/tube, it is almost impossible to kink, and if I don't like the coil I can actually unwind and rewind it . Try that with copper!

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    DAD... not yours.. ah, hell... I don't know...

  • I think you'll find that with the reflux condenser at it's highest setting you weren't actually getting 50:50 ratio. If i were you I'd change the plumbing to test how much you get with 100% take off. It should be pretty easy to do with the fittings I see in the photo (the joys of a modular system!)

    I can get the 0% reflux in my LM, I just don't use the reflux condenser. Like most flutes. I can dial in power from 0.0% to 100.0% I can plot 100% take off at a few different power settings and charge percentages and I'll have a pretty good idea of how much vapor is being produced at any point or setting.

    Any idea what the yellow coating is on the corrugated pipe? If it's inert it might work to your benefit.

  • At it's highest, if it isn't 50/50, it's close enough. I have taken the reflux coil out and capped the top for no reflux as an experiment.

    I'm not one that needs to prove everything to the enth of science and often, unfortunately, get into it with those that do. I truly don't think people know or understand the application of the science they often preach and the limitations of our environment and equipment. If I have a 3" x 36" rig makes 95% at better than 4 quarts an hour, do I care what the reflux ratio is? Naaa....

    As an example, there is a great debate going on about whether or not you can get anything from a packed column without forced reflux? Well yeah, you can. But some are ready to fight that you can't

    If you're a traditionalist and want to have a copper pot still, very cool! If you're wasting time and money winding copper coils because that's the way the "authorities" say to, your cheating yourself.

    I'm afraid I'm the difference between a drinker and a tinkerer. I want the best, most repeatable product for min effort and expense. At this point if I want to tinker, it will be ferments.

    The yellow coating is a painted on plastic...some can be cut off and some are more like an epoxy.

    DAD... not yours.. ah, hell... I don't know...

  • edited January 2014

    I am with @dad on this one. Provided my column temperature and product quality are stable, I don't care what the actual reflux ratio is. As for the need for induced reflux, a packed column will run without it - just slower.

  • Oh heretic...a packed column with no induced reflux...why, why, others would say it is just a "pot still."

    Seriously, I can get 4 plates from my column with no induced reflux fairly easy. But "people" scream, NO YOU CAN'T. Yeah, I can...

    DAD... not yours.. ah, hell... I don't know...

  • edited January 2014

    2 plate packed column, no forced reflux....


    Shows a cold finger there, but i never used it as it had an internal leak. Worked fine without it so i never bothered building a new one. It was run with an end cap in the top triclamp.

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  • edited January 2014

    If I make claims I want to be able to verify them. Otherwise it’s just speculation.
    Of cause you can just run a packed column with no induced reflux.
    It’s called a fractionating column which is a step up from a retort.

    Fractionating column @ Wikipedia

    That’s how I do striping runs as it is much more efficient.
    The more surface area the better efficiency which is why a lot of those old whiskey stills are so tall.

    I personally have found that induced reflux makes bugger all difference to ABV in my rigs at the start of the run especially with a higher % charge. But it does help to concentrate (or compress as you guys insist) all the smaller, lighter fractions but this also seems to be a contentious issue online.
    It also helps to keep the water down at the end of the run which I think is more how you guys seem to run.

    Copper has it’s befits too, it would be silly to write it off without a second thought. It conducts heat much better for one, which can create more passive reflux in a pot. The path to lower water usage in your condenser is through better heat transfer.

    @punkin do your bubble plates still bubble without forced reflux?

    Also, what’s the deal with your plumbing there? Are you cooling and reusing your condenser water?
    That might be a great use for a few shell and tubes that you may have lying around. Water/water or even water/air. Indirect, air cooled still using a computer fan blowing up a vertical 2” tube. We use a similar concept called an attemperation loop.
    I read your mail but I’ll reply to it at home tonight. What you suggest sounds fine. Thanks.

  • edited January 2014

    I don't have those bubble balls anymore mate, but they certainly did bubble when i used them (without forced reflux) I'm not sure they would have been as effective passively in a stainless column though.

    Yes i recirc my cooling water, the 200l drum you see there is balanced with a 500l tank on the other side of the wall. The colling water is pumped out of the drum (or was) and hot water was run back into the tank.

    The tank would layer quite well and it would only be on a long reflux run in summer that i would have to top it up from the bottom with cooler water.



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  • The main issue here is speed. Provided the column can loose enough heat to create natural reflux you are OK. If it can not then you need to add in induced reflux. You can run any column without induced reflux but it might be very slow. Copper is more helpfull in this context than stainless. It is always good to include the option fot instantly switching the still into 100% reflux, just as a safety option. If you can fit it into your configuration. :)

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