Sizing Dephlegmator

[flyingdutchman]

Hi,
I did do some searching and reading before posting this question so as not waste peoples time with things that have already been posted. I would like to summarize what I think to be true so if I am off track you can correct me? My understanding is that the purpose of a dephlegmator is to condense some but not all of the vapor to liquid w/out obstructing the overall vapor path. Often this is used for a plated column or flute build so as to prevent flooding of the plates? Possibly how much we want condensed could be dependant on build size and plate types? So I am interested in dephlegmators and would like to know .....

1) How does one goes about sizing it? From the parent site I see there is a great calculator for sizing reflux condensers but that seems to be laid out for 100% reflux which seems to be more than is required. It seems like if the condensor was over built it might be rather difficult controlling it to get just a small amount of reflux? Do people start with some rough estimate like 50% reflux?? Or is it extremely variable and strictly based on build size and type?

2) I see others have mentioned using a coil type condenser or maybe even a 2 stage coil type condenser. Would a single wound internal coil (say 1/4" properly sized) work or even 1/4" external coil solidly bonded to the outside of the column. I see a couple of people posted about trying this but never saw any results.

Thanks

[Usge]

I'm no expert on deplegmators, but I've built a couple and tested them.

You can stick anything on top of a column/tube that you can cool and it will reflux (to varying degress) distillate back down the column, and allow certain lighter vapor components to pass. I've seen everything from just 1/8" or 1/4" soft copper coil wrapped like a snake on the outside of the copper column or lynearm, to as minimal as just having a couple of small tubes pass through the head near the take off point. But, the dephlegmators everyone is using today...function in two ways....first: they are capable of "Total" reflux...returning everything back down the column allowing nothing to pass through them. Second: they are adjustable/variable after that point, such that they can be balanced between returning distillate to the plates (or back down the column packing), and allowing certain portions of the vapor to pass thru to get condensed. In that way, they sort of act as a CM "gate" as well.

You "could" have a dephlegmator that was tuned to a certain range..that always functioned the same way (allowing only certain portions of vapor to pass). But, the design everyone is using lately is the "shotgun", which is fully capable of shutting down the vapor and returning everything to put the column under total reflux, and then adjusting it to allow flow after that. AS to size...that's normally "square" (ie., 4x4 in a 4 inch column, 2x2 in a 2" column). The issue with them is, the more cooling (knockdown) power they have..the harder they are to tune after (ie., you have to just use barley a dribble into them to even get the distillate to flow) — ie, they are too efficient. On the 2incher I built...I started at 3.75" long and had fits trying to control water flow through it. It "easily" knocked down everything my stove could throw at it, but even with the water flow "off" it would still take a few mins before distillate would start to come out. I surmised it was just too efficient, knocking down too much wood. So, I shortened it to 2". At 2" (square) it would "just" barely knock down full reflux at the start if I turned up the water flow all the way. It was better in that I could ease off the water flow and get some distillate out. BUt, still hard to control because the flow through the deplegmator was just not enough to really keep it even (it kept crapping out on me...changing flow rates, etc through vacuming, etc. through the various connections/flow paths). So, I redesigned it using a 3-way ball valve and using output from the condenser for flow. This one flows very well, no issues there.

I found using water from the product condenser output to feed the cooling to dephlegmator has some advantage in the way in which they work together. The less vapor that reaches the product condenser (passes the dephlegmator) the cooler the water will be in the product condenser (and therefore to the dephlegmator). As more vapor passes the dephlegmator ...(ie., when you want/need "less" reflux), the vapor that comes over heats the water in the product condenser and helps with the flow issues inherent to very efficient reflux condenser designs like the shotgun. If you want to squeeze tails later in the run...as you increase the flow of water to the dephlegmator, the vapor slows, the temp of the water in the product condenser begins to drop again...adding more reflux value where/when it's needed. This helps with some of the inherent problems of having a pass-through reflux condenser that is efficient enough to knock down everything...when you still need some sensitivty to it after that point.

Having said all that, and having spent countless hours building and tinkering with these things...I would say that at a smaller level...a simple double would coil or single coil with cold finger 6-8" long would probably do..albeit with slightly less fine tuning control (which may or may not be necessary depeding on what you are trying to do). The trick would be placement inside the tube in regards to the lynearm (take off point). If you want to go through my pain and suffering...here's the thread

http://homedistiller.org/forum/viewtopi ... 17&t=22424

[NcHooch]

'course th size would pretty much be determined by the amount of vapor you have running up the column, right? ...Shotguns seem to be the most popular when used with flutes, their design and form fits nice into the flute column. I suspect the shotgun is the most efficient as well. Concerning the size, I'd venture to say that you could prolly take a SWAG (scientific wild ass guess) concerning the size, and then divide by 2, and that would be darn near perfect.

[flyingdutchman]

Hi Usge. Thanks so much for your reply it was extremely helpful. I had previously seen your post but will go back and reread it again. I can certainly see where

The issue with them is, the more cooling (knockdown) power they have..the harder they are to tune after (ie., you have to just use barley a dribble into them to even get the distillate to flow) — ie, they are too efficient.

It seems like once the flow is down to a dribble it can create alot of problems. I think the 2x2 or at least the ability to

"just" barely knock down full reflux at the start if I turned up the water flow all the way.

is a great refernce point for sizing the condensor. I reall liked your input about feeding the dephlegmator from the output of the product condenser. I never realized it would act as a sort of self controling feed back loop that is very slick I thought maybe one way to control the dephlegmator was sort of like this for cm rigs I saw in "the compleat distiller" by Nixon and Mcgraw.

(The image is his I got online). The internal coil dephlegmator was an idea from "peters still" on the parent website http://homedistiller.org/equip/photos-reflux" onclick="window.open(this.href);return false;" rel="nofollow. I only considered this as my brazing skills are non existant. I can solder ok as I used tyo be a plumbers apprentice for a couple of years and weld (stick/mig) fine just but never learned to braze which seems like it lets me down as far as a shotgun condensor. Ultimately I would like to build a plated column (no windows, a flute looks really beautiful but probably outside my skill set). I havent done enough research to decide if I would want bubble plate or sieve plates and probably thats a topic for another day once I am a little more up to speed on the topic. Thanks again I appreciate it.
Ps I have tried the swag method in the past but in my hands it usually results in doing the job twice. I have to agree cutting the estimate in half is probably a good idea in this case i usually over build things lol