Avoiding air in the top of Dephlegmator

[Talix]

Hi guys

On my way to a completely modular flute. I've gotten a fair way but want to make sure that I avoid the worst pitfalls...

I'm now up to putting together my shotgun dephleg. It will consist of a 150mm section of 4" pipe, and 12 lengths of 1/2" tube. I'm aiming for about 100mm of total cooling jacket length. I'd also decided to go with baffles to improve efficiency and reactiveness. However, an issue I've suddenly become aware of is that if using cross flow (inlet at the top, outlet at bottom) the gasses suspended in the water will accumulate at the highest point of the RC, slowly leading to a decrease in efficiency toward the end of the run...

Now, I can just swap the in- and outlet, no biggie with the cross flow I've heard... But should I then also discard the baffles? It seems as if baffles are just to increase the effectiveness of cross flow heat exchange. It might even be counter productive having them if in/out are reversed.

What do you think?

[Talix]

For your reference, I've attached the original design as a pdf.

[corene1]

I had that problem also, but I re-plumbed my dephlag and it works quite well now. I plumbed the water in at the top and out at the bottom just as you described, but I put the flow control valve on the exit and ran the water pressure in the top. I also put a small bleeder valve on the top opposite the inlet. So when I run the still I turn on the water with the exit valve closed and bleed all the air out of the dephlag using the small bleeder . This guarantees no air in the chamber and it gives very finite control of the water temps in the dephlag itself since it constantly under pressure from the fill side . .

[cranky]

You know, I have read many posts where people insist you have to go in from the top and out the bottom. I don't think it is as critical as people seem to think. I believe the cold water will naturally sink to the bottom anyway and hot go to the top. I plumbed mine in through the bottom because I don't want the water in my dephleg pressurized, I worry it might result in a leak. I have had no control issues whatsoever by plumbing in from the bottom and out the top and I know for certain no matter what the dephleg will be full of water.

[Talix]

I had that problem also, but I re-plumbed my dephlag and it works quite well now. I plumbed the water in at the top and out at the bottom just as you described, but I put the flow control valve on the exit and ran the water pressure in the top. I also put a small bleeder valve on the top opposite the inlet. So when I run the still I turn on the water with the exit valve closed and bleed all the air out of the dephlag using the small bleeder . This guarantees no air in the chamber and it gives very finite control of the water temps in the dephlag itself since it constantly under pressure from the fill side . .

You know, I have read many posts where people insist you have to go in from the top and out the bottom. I don't think it is as critical as people seem to think.

Yeah, that's what I figured as well... Baffles are out I guess, I can make a few more perf. plates out of the copper sheets instead

I don't think I'll use a bleed valve though. Just cracking the exit valve open should fill the chamber, no?

[Saltbush Bill]

The water on my the dephlegmator goes in the top and out the bottom.
Due to the way that I built mine I was worried that the dephlegmator would get an air bubble in the top of it.
Most people said that it would not happen, water pressure alone would be enough to blow any air out of the system as long as you opened it up to full reflux at the beginning of the run.
In short pumping a lot of water through the the dephlegmator in a short time would blast any air out.
I'm not that great at doing things the way others say I should , so I went right ahead and put in a air bleed in the top of my the dephlegmator, glad I did ....lots of air escapes when I bleed it off.
I often wonder how many dephlegmators dont preform to optimum because they have air caught in them.

[Yummyrum]

I've seen Salty bleed that valve and there is a lot of air comes out . .... so it is a genuine issue .
Corene does the same as Salty with a bleed valve .

I'm kinda like Cranky , I use the cold in at the bottom , hot out at the top with the valve on the outlet at the top to keep the deflag full and not have any syphoning effect ....: iff'n that is a concern .

I don't have mains pressure so not worried about leaks ( LOL I'd Bloody hope my brazing would be able to cope ) poke poke @Cranky


All methods work at the end of the day . Don't get too hung up on it .
What you should be thnking about is flow adjustment control . Needle valves will be the difference between frustration and pleasure . Needle bypass for quick full refux is nice also .

Don't worry about baffles . ... seriously .... at 100 mm long , vapour speed "blow through" will be your limiting concern long before cooling efficiency becomes an issue

And before vapour blow through becomes an issue , pulling tails through your run will be .
What I'm trying to say is you deflag will be fine for normal flute operation but controlling the minimal coolant flow that is required really is the main thing you should be worried about .

[shadylane]

+1 Yummy
On a side note.
For several reasons, I prefer a dimroth style of dephlegmator better than a shotgun
Especially on a plated column

[Saltbush Bill]

What you should be thnking about is flow adjustment control . Needle valves will be the difference between frustration and pleasure . Needle bypass for quick full refux is nice also .

Don't worry about baffles . ... seriously .... at 100 mm long , vapour speed "blow through" will be your limiting concern long before cooling efficiency becomes an issue

Iv'e been trying to say that for ages ......you do it so much better Yummy

[cranky]

I don't have mains pressure so not worried about leaks ( LOL I'd Bloody hope my brazing would be able to cope ) poke poke @Cranky

Have you seen the crappy solder work on my columns? I never had trouble with the shotgun leaking but had a hell of a time with the copper to stainless connections on my dimroths. Lots of people do have trouble with leaks, I run a pump with 11 Ft head lift that I'm pretty sure puts out more pressure than I would be comfortable with. My backup pump is capable of 24 Ft head lift and puts out so much pressure that if it is run without a relief valve it blows fittings apart, sprays like a fire hose and empties a 55 gallon reservoir in seconds. I seriously doubt my crappy solder work could stand up to that.

Just to fill people who may not have seen my setups, I run a shotgun on top of my neutral column and a dimroth in my flute. I like the dimroth best but have no complaints about the shotgun. I think the initial control on the dimroth might be a bit faster to react to adjustments but once the shotgun is up to temp it is fine.

[Euphoria]

FWIW, Just my two cents, but I have always run my dephlegmator cooling water in from the bottom and out the top, with my metering valve on the upper outlet water line. I have never found it to run erratically, nor have I ever had a temperature stability control problem. I run it on a 26 gallon boiler and a 4" fluted column. It has always worked quite well for me. It also helps greatly to have the cooling water supply/return lines split between the dephlegmator and the condenser, rather than running them in series. On mine, I have separate metering control for each off the common "wye" supply line from my cooling water reservoir.

[still_stirrin]

Another way to do it, if you still want the water to be counter flow (cold in at the top and warm out at the bottom) is to route the water discharge line up and over the top of the dephlag. That way, when the dephlag fills with water, the level of water is higher than the inlet even though the inlet is on the top of the dephlag.

I do it that way with my concentric RC. The condenser fills completely with water before the water flows out the discharge line.

“Gravity”....it’s not just “a good idea”....it’s the law!
ss

[captainshooch]

https://youtu.be/Vj6w5xOIxIo" onclick="window.open(this.href);return false;" rel="nofollow

[captainshooch]

I fill all my condenser wether is a PC or a RC from bottom with needle valve on top to regulate flow on output side.
Works just fine.

[captainshooch]

You can fill from top also.
https://youtu.be/Fbgbp2zCJYQ" onclick="window.open(this.href);return false;" rel="nofollow
I rather not.

[Bushman]

I have a shotgun dephlagmater, both fill and exit are at the top but the fill port tube extends to the bottom of the dephlagmater thus is the same as a bottom fill. Has worked great with no problems. Below is a drawing of my original plans that explains the build. Actual build, the second picture has fewer tubes as tests showed I didn't need the amount on my original drawing.

image.jpeg (14.9 KiB) Viewed 2440 times

[captainshooch]

My mash rookie condenser i got from 700G looks just like that bushy. It fills from bottom also. Best way to purge air out IMHO

[Saltbush Bill]

Thats the same design as mine to Bushman, The difference is mine fills from the top, one of the reasons I needed a air bleed valve. That design of dephlegmator with both tubes going in the top was fairly common back then.

[Bushman]

My mash rookie condenser i got from 700G looks just like that bushy. It fills from bottom also. Best way to purge air out IMHO

MR and I built them together. I did the CNC cutting and he had the design idea.

Thats the same design as mine to Bushman, The difference is mine fills from the top, one of the reasons I needed a air bleed valve. That design of dephlegmator with both tubes going in the top was fairly common back then.

It drops in the column through the top. If you look closely above the dephlagmater the plate that sits down on top of the column has a grove I milled to hold my 4" gasket. Serves like a ferrule and I seal it with a tri-clamp. Below are the milled pieces, the two smaller ones made up the dephlagmater and the larger one is the one I am talking about.

image.jpeg (27.56 KiB) Viewed 2422 times

[Saltbush Bill]

Drop in was the way it was done 7-8 years ago, how things have changed.

[cede]

For several reasons, I prefer a dimroth style of dephlegmator better than a shotgun
Especially on a plated column

Any picture ?

[Bushman]

Drop in was the way it was done 7-8 years ago, how things have changed.

Was an easy solution! Just cut the 4" tube lengthwise and soldered it a bit smaller to slide in.

[shadylane]

I've been plumbing the dephlemator with cold water in the bottom and hot out the top
Here's a pick of a 4" shotgun next to a 4" dimroth dephleg of similar knock down power.

[pfshine]

I am only going to build coil condensers from now on. It gets rid of the air problem, responds much faster and is far more efficient. Besides all that it's really simple to build and nowhere to leak from inside the column. I do think the deflag is a sexier build, but you can't see it in action with a sight glass like you can a coil. I always do cross flow and my control valves are always on the outlet so that you can't starve the system.

[cranky]

This is what mine looks like

It was much easier to make that a shotgun that's for sure

[Euphoria]

A Frankenphlegmator! Sorry, I just couldn't resist Cranky.
It's aliiiiiiive!!!!!