Yummy's always Improving Deflag coolant control

[Yummyrum]

Controlling A deflagmator is a pain in the arse at best . It requires a critically adjusted water flow which takes a while to hone in on mostly due to the huge lag time between adjusting and seeing change in output .

Basically there are three states when running:
1) Full reflux ....this is usually at the start to allow the plates to load and equalize
2) Partial reflux ...this is when you draw off product and occurs during most of the run
3) No reflux ......this is when you want to run in pot still mode or at the end of the run where you might want to strip remaining tails

You can achieve all this with just a single coolant control valve but if you need to quickly switch from one state to the other and back again , you spend a ridiculous amount of time re- fiddling the knob to get it back to where it was running nice .
An example might be the cell phone rings and you need to put the still into full reflux while you are taking a call .


When taking off product the flow required through the deflag is extremely small , basically a dribble .
I originally used a gate valve ....but it was horrible , so much back lash ,

then a ball valve ....it was better in that regard but still touchy as all shit ......and finally got a needle valve . Each improved the situation but even the needle valve was touchy mainly because I was a scabby bastard and bought a cheap one

At this stage I could see the merit of being able to switch quickly from full reflux to adjustable ( states 1 and 2 above )
I fitted a bypass valve across the needle valve .This was a major improvement .

This arrangement has worked well but the needle valve sucked due to its poor quality and the act of placing your hand on it will alter the setting and the output flow will change

That's when Copperhead road gifted me a Parker needle valve ( love you Copperhead ...that's and Aussie thing ) so it was time to fix this mess up and revue the situation .

Seeing as the Parker Needle valve needed a whole new plumbing make-over , I decided to fork on a three way valve .These incidentally aren't cheap .
For those who don't know , a three way valve has three positions . It has one input/output that can switch between one of two other ports or neither. So by incorporating it I can satisfy all three states above

The observant may have noticed that on the first pic the water lines are on the same side where as in following pics there is an input feed added on the opposite side with the original lower port being capped off .

I subsequently used that lower capped port as a physical mounting point to secure the plumbing ...so although it looks like there is a connection here , it is only an anchor point ....no water flows .

So after looking at all the shiny new plumbing I decided to give the old Deflag a polish too ....just for CopperHead road

[still_stirrin]

I like it. Form, function, and fashion!

So, what’s in your deflag (sorry, I didn’t go back to the build thread)? It’s obviously 4” ID and it looks to be roughly 6” long. What size and how many vapor tubes inside?

Also, boiler kW rating? What is the deflag’s full knock-down power rating?

With the improved valve design/solution, you have much control, including the fine control for the CM process. So, the vapor tube and conducting surface areas must be well designed and built, making the heat transfer efficient and balanced for your boiler.
ss

[Yummyrum]

SS , I built the deflag about 4-5 years ago and just copied others at the time . It has 7 x 3/4” OD pipes in it and although it looks close to 6” long , the ends are not as they look . It’s actually closer to 4” .

And while it works on the Flute , it is not ideal . It can knock back more power than I effectively ever use because if I run harder , I suffer entrainment so in this application it works .
But the quantity of water in it is large meaning that any adjustment takes ages to change the output flow as the large body of water slowly changes temp .

Where I do have a problem with this deflag is when I use it on my 4” packed section . In this application I would like to run with heaps more power to get the reflux ratio up but I am limited by the high vapour flow simply blowing straight through regardless of how much cooling water is flowing .

So I have been thinking of replacing it with a lot more tubes so there will be more are and therefore a lower vapour speed and with much less water in the deflag , response time should improve

Sorry I can’ give you power figures as I run on gas

[Yummyrum]

This is the bottom , you can see that it isn't the full length of the shell.

But when you look at it , there is only 20% area for the vapour to go into ....I guess this is why I have so many problems with vapour blow threw . ...Hence the logic to add more pipes .

Originally I wanted to add this to it and have adjustable water level but I never bothered . That is also the reason there is a plate soldered on the side covering the slit that would have been open to the attachment .

I think that my adjustable level RC would have worked and I may try it some day just for shits and giggles ...but I don't think it will be as wonderful as I originally imagined

[still_stirrin]

This is the bottom , you can see that it isn't the full length of the shell...But when you look at it, there is only 20% area for the vapour to go into...I guess this is why I have so many problems with vapour blow threw...Hence the logic to add more pipes.

A couple of thoughts regarding dephlemator design: vapor flow area should be optimized to allow the maximum vapor production from the boiler at the appropiate vapor velocity. So, more tubes is good. But conduction surface area between the vapors and the coolant should also be maximized as well. Therefore, a longer tube bank is advantageous. What you want is a longer dwell time to give the vapor opportunity to lose its heat to the condenser. This reduces the liklihood of vapor blowby even at higher power settings.

You’ve said that the water volume in your deflag is so great that it pulls too much heat from the vapors until the vapor production pushes vapor out of the top. Indeed, the larger reservoir of water is a great heatsink for power but it is not the most efficient with the heat input. A smaller water jacket (more, possibly smaller diameter tubes) would work more efficiently, increasing conduction surface area, vapor dwell time and allow a better temperature gradient through the condensing cycle. Also, a baffle or two would create turbulence (mixing) in the coolant flow to eliminate localized hot spots.

The deflag is a complicated shell & tube HEX design, but can be optimized for the desired performance given the boiler’s range of production. A 4” shell is capable of a lot of power.

These are just some thoughts regarding HEX design. Obviously, your deflag works well within the range of operation you like to run it at.

Cheers.
ss

[shadylane]

Your the man Yummy
The best way I've found to control a defleg was to use a coil instead of a shotgun.
A coil is physically shorter, lighter, easier to build, less likely to leak and has a faster throttle response.
The shotgun is sexier. I leave it on the shelf for friends to look at

[Copperhead road]

Love ya work yummy, it’s looking flasher than a rat with a gold tooth.