VM Valve question

Vapor, Liquid or Cooling Management. Flutes, plates, etc.

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eternalfrost
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VM Valve question

Post by eternalfrost » Sat Dec 20, 2008 11:32 pm

im looking into tuning my bokakob into a VM and wanted some input on what to look for in a valve as that will be the main purchase for this project.

from what i can gather, SS gate valves are best since thier seals are PTFE and have the smallest surface area. they also create the least turbulance (effects debatable)
or a SS ball valve which has a bit more seal exposure

from what ive seen it seems like there isnt any appreciable difference in performance between ball and gate. comments?
also, for a 2 inch column, what would be the proper size for the takeoff branch on the T and what size valve? im wondering if there would be any change in performance between say branching off at 2 then reducing to something smaller then the valve, or just using a 2XsomthingX2 T from the start.

this is an ongoing lazy project over the holidays. mostly just wondering whats best to look for as a browse over ebay and the scrappers. what would be an ideal rolls-royce valve, an average valve, and what to steel clear of

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Re: VM Valve question

Post by manu de hanoi » Sun Dec 21, 2008 12:50 am

eternalfrost wrote:im looking into tuning my bokakob into a VM and wanted some input on what to look for in a valve as that will be the main purchase for this project.

from what i can gather, SS gate valves are best since thier seals are PTFE and have the smallest surface area. they also create the least turbulance (effects debatable)
or a SS ball valve which has a bit more seal exposure

from what ive seen it seems like there isnt any appreciable difference in performance between ball and gate. comments?
also, for a 2 inch column, what would be the proper size for the takeoff branch on the T and what size valve? im wondering if there would be any change in performance between say branching off at 2 then reducing to something smaller then the valve, or just using a 2XsomthingX2 T from the start.

this is an ongoing lazy project over the holidays. mostly just wondering whats best to look for as a browse over ebay and the scrappers. what would be an ideal rolls-royce valve, an average valve, and what to steel clear of
gates have a screw system to move the gate, and are less sensitive than the ball therefore more accurate(10 wheel turns vs 1/4 turn). Moreover there is a plastic joint around the ball in ball gate that is often of unknown composition.

Balls, screws n' gates make the world go round.

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Re: VM Valve question

Post by minime » Sun Dec 21, 2008 4:05 am

I've been using ball valves when building VM columns because they are light weight. I originally feared they might not be accurate enough but I've found they work OK because VM columns can be adjusted in very coarse ratios without suffering instability.
As for appropriate branch size I've discovered large is better. VM is primarily a vapor stream splitter so reflux ratio control comes entirely from the valve. If the outlet branch is undersized the max output will be preset. Much better to have more than you need versus too little. After running this style column I was so impressed I built another. So a 2 inch column should have a 2X2X2 tee. The branch can be immediately reduced in size right down to 1/2" for the product condenser and valve. I found this arrangement to work very well. It is a scaled up version from The Compleat Distiller.

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Re: VM Valve question

Post by eternalfrost » Sun Dec 21, 2008 11:19 am

thats interesting minime, ive never seen one quite like that before.

Image

where the takeoff isnt reduced until AFTER the elbow. do you notice any significant performance difference to this?
seems like it might take advantage of the "alcohol vapors sink" phenomenon everyone keeps mentioning with VMs

all the other ones ive seen with reducers have been in the horizontal part and it just seemed kind of pointless to me since the takeoff is ultimately restricted at the ball valve anyways so why bother not just going straight off the T

that head of yours makes sense to use a reduser to me tho

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Re: VM Valve question

Post by minime » Sun Dec 21, 2008 11:45 am

eternalfrost wrote:thats interesting minime, ive never seen one quite like that before.
where the takeoff isnt reduced until AFTER the elbow. do you notice any significant performance difference to this?
seems like it might take advantage of the "alcohol vapors sink" phenomenon everyone keeps mentioning with VMs
all the other ones ive seen with reducers have been in the horizontal part and it just seemed kind of pointless to me since the takeoff is ultimately restricted at the ball valve anyways so why bother not just going straight off the T
that head of yours makes sense to use a reduser to me tho
I have not experimented with the valve before the reducer so I can't compare. I do know this arrangement works beautifully and can be driven WAY past optimal. I was able to drive it all the way to 5500ml per hour but purity was down under 90% and temperature was impossible to control reliably at that rate. Producing azeotrope at 3800ml per hour was extremely stable with this arrangement and R/R is super easy to set and forget. Not quite as easy as my inverted funnel but that column has a predetermined maximum output rate because of the branch size.

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Re: VM Valve question

Post by maoule » Sun Dec 21, 2008 1:07 pm

I think one issue that others have brought up is that while the unit equalizes, product collects in the vertical past the elbow. I have 3/4" after the elbow and get about 100-110 ml of product when I open the valve. I just toss it with the foreshots. So remember to open the valve enough to clear the line before returning the normal take-off rate.
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Re: VM Valve question

Post by minime » Sun Dec 21, 2008 1:39 pm

maoule wrote:I think one issue that others have brought up is that while the unit equalizes, product collects in the vertical past the elbow. I have 3/4" after the elbow and get about 100-110 ml of product when I open the valve. I just toss it with the foreshots. So remember to open the valve enough to clear the line before returning the normal take-off rate.
Maoule, that's lots more buildup than I get. How long are you stabilizing for? You could also insulate the branch. Once it's up to temperature it shouldn't collect any more liquid.
How many runs do you have now?
Did you experience anything problems like the one described in this thread? http://homedistiller.org/forum/viewtopi ... =17&t=7350" onclick="window.open(this.href);return false;" rel="nofollow

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Re: VM Valve question

Post by eternalfrost » Sun Dec 21, 2008 2:18 pm

interesting point about pooling above the valve during equlization. i am a bit of a fanatic about insulation tho so the entire thing is going to be covered up anyways :wink: research habits...eliminate the variables!

one other question, how close is it safe to have the reflux condenser to the vapor split? in my mind if it were very close to the T it would 'steal' vapor from takeoff arm. obviously in the extreme case if the condenser were level with the takeoff, NO product could be removed

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Re: VM Valve question

Post by minime » Sun Dec 21, 2008 2:36 pm

eternalfrost wrote:interesting point about pooling above the valve during equlization. i am a bit of a fanatic about insulation tho so the entire thing is going to be covered up anyways :wink: research habits...eliminate the variables!

one other question, how close is it safe to have the reflux condenser to the vapor split? in my mind if it were very close to the T it would 'steal' vapor from takeoff arm. obviously in the extreme case if the condenser were level with the takeoff, NO product could be removed
From my experiment with the slant plate VM that was doomed to failure, I did uncovered this little tidbit of information. When I first fired up I could not get the slant plate to output more than a couple of drops per second. The placing of one scrubber between the coil and plate got me a small stream.
I'm fairly certain the expanding vapor will try to divide equally between the reflux coil and the branch if they are the same size. You could leave room for one scrubber if you're not concerned about height but not really needed. You need at least 2 to 1 R/R to get to 95+ anyway.

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Re: VM Valve question

Post by eternalfrost » Sun Dec 21, 2008 6:00 pm

would the head pictured above be considered to have a 1:1 min-RR? or perhaps a little higher like 1.5:1 due to resistance from the valve/reducer?

its just gauged by the amount of vapor hitting each condenser when the valve is full open yes?

and you want it to be as close to unity as possible, because you can always increase the ratio by closing the valve. having a min-RR that is too high simply forces you to run very slow (and clean)

right?

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Re: VM Valve question

Post by maoule » Sun Dec 21, 2008 7:08 pm

minime wrote:
maoule wrote:I think one issue that others have brought up is that while the unit equalizes, product collects in the vertical past the elbow. I have 3/4" after the elbow and get about 100-110 ml of product when I open the valve. I just toss it with the foreshots. So remember to open the valve enough to clear the line before returning the normal take-off rate.
Maoule, that's lots more buildup than I get. How long are you stabilizing for? You could also insulate the branch. Once it's up to temperature it shouldn't collect any more liquid.
How many runs do you have now?
Did you experience anything problems like the one described in this thread? http://homedistiller.org/forum/viewtopi ... =17&t=7350" onclick="window.open(this.href);return false;" rel="nofollow
No, I'm wondering if Jippe's boiler outlet (looks like 1"-1 1/4" to 2") is causing some problems. My old water heater unit (3/4" output to 1 1/4") was a real bitch to keep stable.
Anyway... 2 runs on my VM, stabilizing for minimum 30 min. and the last run was feints that stabilized for 2 hrs. It could be that the >7000w of heat need to be slowed a bit before hitting temp. I'll check that later this week; however, there will be some pooling regardless.
As far as the RR goes in a VM, I have questioned it in other threads: Destructomutt posited that the RR is a factor of the smallest opening in the take-off (3/4" to 2" is a 7.5:1). Is this correct or does the collapsing vapor factor in? Does it matter what happens after the condenser? I reduce to 3/8" after my condenser. Fact of matter, does the RR really matter if I plan to strip sugar washes w/my pot head and run reeeeal slow w/the VM for extra neutral?
Hopefully, this post hasn't steered the topic too far afield, but if we discuss the theoretical, it would be nice to conclude at least the basics.
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Re: VM Valve question

Post by eternalfrost » Sun Dec 21, 2008 9:00 pm

maoule wrote:It could be that the >7000w of heat need to be slowed a bit before hitting temp.

damn 7000W is a fucking trojan! i have 5500W and its almost too much to handle for stripping much less refluxing. i only use 750-1000 on the reflux run


As far as the RR goes in a VM, I have questioned it in other threads: Destructomutt posited that the RR is a factor of the smallest opening in the take-off (3/4" to 2" is a 7.5:1). Is this correct or does the collapsing vapor factor in? Does it matter what happens after the condenser? I reduce to 3/8" after my condenser. Fact of matter, does the RR really matter if I plan to strip sugar washes w/my pot head and run reeeeal slow w/the VM for extra neutral?

the problem with the RR ive seen in my readings is people haveing a overly high minimum ratio, forcing them to run much slower then necessary to get 96.5%. now that might not be a problem to some but idealy you would want to at least be ABLE to open her wide enough to start loosing purity, then crank the ratio back up to hitting azeotrope to maximize speed and heat efficiency. the idea is you can always increase the RR by closing the valve but going the other way you eventually hit a wall with the valve full open, and you dont want that wall to be restricting you

Hopefully, this post hasn't steered the topic too far afield, but if we discuss the theoretical, it would be nice to conclude at least the basics.

i dont think it off topic at all, in fact one of my original questions was about the whole RR issue. personally, my goal is to make a VM head that can hit azeotrope at maximum output, while having the option to crank up the RR and "over-reflux" it to see if that improves final tastes at all. just trying to find the way to make that happen

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Re: VM Valve question

Post by maoule » Mon Dec 22, 2008 3:14 am

eternalfrost wrote:
maoule wrote:It could be that the >7000w of heat need to be slowed a bit before hitting temp.

damn 7000W is a fucking trojan! i have 5500W and its almost too much to handle for stripping much less refluxing. i only use 750-1000 on the reflux run

the problem with the RR ive seen in my readings is people haveing a overly high minimum ratio, forcing them to run much slower then necessary to get 96.5%. now that might not be a problem to some but idealy you would want to at least be ABLE to open her wide enough to start loosing purity, then crank the ratio back up to hitting azeotrope to maximize speed and heat efficiency. the idea is you can always increase the RR by closing the valve but going the other way you eventually hit a wall with the valve full open, and you dont want that wall to be restricting you

Hopefully, this post hasn't steered the topic too far afield, but if we discuss the theoretical, it would be nice to conclude at least the basics.

i dont think it off topic at all, in fact one of my original questions was about the whole RR issue. personally, my goal is to make a VM head that can hit azeotrope at maximum output, while having the option to crank up the RR and "over-reflux" it to see if that improves final tastes at all. just trying to find the way to make that happen
The 7000w (2 heating elements)is just to speed the heat up phase. Once there, I back it way down. I only have a coupla runs with the new power controller I got from pinto, but the last pot still (UJSM) spirit run I did, I was running it at <200watts. That controller is awesome: it'll run from 238 volts down to 1 volt.
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Re: VM Valve question

Post by minime » Mon Dec 22, 2008 3:19 am

Since I've actually toyed with several configurations of VM I can say without hesitation and I have stated this in another thread.
Credit to Manu who advised when I originally started down the VM path
The size of the VM branch is critical to effective operation. The branch may be immediately reduced in size without consequence however. I have proven this on three separate occasions and found no detectable difference in output speed when reduced to 1/2 inch. It may be possible to reduce to an even smaller valve and liebig size but I have not attempted to do so.
EF's concern about vapor having immediate access to the reflux coil is valid and can be solved with the addition of one scrubber above the branch if required. I have found the minimum R/R to achieve 95+ with 60" of packing is 2 to 1 running a stripped charge in the boiler.
With 60" of packing the column is simply running itself once the initial valve opening is set. The quality of alcohol does not change until late in the reduced output stage of the run. The consistency of R/R without manual intervention is remarkable with VM and minor fluctuations in heat and vapor speed have no impact at the collection jar whatsoever. It may even be possible to operate VM on a cycling stove top. I will be testing the possibility come spring.
Both VM and LM have similar or identical collection rates and either is a good choice for high quality neutral. Having experience on both platforms I am completely convinced VM is superior in ease of operation and ease of construction. The most difficult aspect of a VM build is winding the reflux coil. It can be done completely with off the shelf copper parts.

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Re: VM Valve question

Post by eternalfrost » Mon Dec 22, 2008 9:26 am

thanks for all your wonderful info minime, both here and all those epic threads of yours. 8)

been thinking it over and what you say about the T diameters makes alot of sense really. it seems like the hard part is making the vapor bend the corner. the large take off diameter makes it easier (probably nearly even resistance to both paths) to do so. then the vapor can sort of wait in the 'staging area' near the reducer until it is sucked in by the collapsing vapor in the liebig.

no i am confident of my knowledge of the whole VM thing. im unhappy with my LM at the moment and first plan to extend the height another 24 inches (untill i hit the ceiling 8) ) to see if that will fix my problems. if not, ill be changing the head to VM

in all honesty, even if it does work ill be making a VM head eventually... :roll: love to tinker and the VM idea just seems so elegant to me. the engineer/scientist in me much prefers it over my solder-splattered, hacked together, needle-valve-using Bok head heh

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Re: VM Valve question

Post by snuffy » Tue Dec 23, 2008 6:55 am

I've been corresponding with Mike Nixon about VM. He says that turbulence at the takeoff point is critical to the proper operation of VM.

It can be as simple as having a lip below the takeoff point or an inverted elbow. If the flow is laminar at the takeoff point, the majority of the vapor will stick to the center of the column and the takeoff elbow will be relatively stagnant because of the boundary layer effects.

minime's large tee will have considerable turbulence because of the radical change in cross-sectional area in the middle of the tee.

One way to test how turbulence works: if somebody has a VM head with unsatisfactory performance, add a flat cross bar three column diameters below the takeoff. It doesn't need to be very wide -- 5% - 10% of the column diameter should be enough. It doesn't need to be big enough to block the passage, only to cause the streamlines to swirl around. This should cause plenty of turbulence and should produce an observable change.
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Re: VM Valve question

Post by minime » Tue Dec 23, 2008 8:55 am

snuffy wrote:I've been corresponding with Mike Nixon about VM. He says that turbulence at the takeoff point is critical to the proper operation of VM.
One way to test how turbulence works: if somebody has a VM head with unsatisfactory performance, add a flat cross bar three column diameters below the takeoff. It doesn't need to be very wide -- 5% - 10% of the column diameter should be enough. It doesn't need to be big enough to block the passage, only to cause the streamlines to swirl around. This should cause plenty of turbulence and should produce an observable change.
Would have been a good test for the slant plate VM design I tried. I still have that head and just might give that a try come spring. I'd love to see the slant plate design mature into something useful. I had such high hopes for it.

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Re: VM Valve question

Post by rad14701 » Tue Dec 23, 2008 4:47 pm

minime wrote:I'd love to see the slant plate design mature into something useful. I had such high hopes for it.
Ditto...

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Re: VM Valve question

Post by HookLine » Tue Dec 23, 2008 5:05 pm

if somebody has a VM head with unsatisfactory performance, add a flat cross bar three column diameters below the takeoff.
By unsatisfactory performance do you mean in terms of output rates, and maybe control of the still? I can't see how lack of turbulence above the packing makes any difference to final quality.

And three column diameters is a fair bit of lost packing height (150 mm loss for a 50 mm diameter column, that is not an insignificant amount). Wouldn't the vapour be fairly turbulent immediately after exiting the packing anyway?
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Re: VM Valve question

Post by HookLine » Tue Dec 23, 2008 5:10 pm

rad14701 wrote:
minime wrote:I'd love to see the slant plate design mature into something useful. I had such high hopes for it.
Ditto...
Ditto that ditto.

I think there is serious potential in that slant plate idea yet. Roll on spring for Minime!
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Re: VM Valve question

Post by snuffy » Tue Dec 23, 2008 7:46 pm

I mean unsatisfactory like poor control or too little output.

In turbulent flow, the pressure in the column will predominate -- thus pushing the vapor out the takeoff. In laminar flow, a side leg can have a much lower dynamic pressure than the main flow line, even negative.

According to my Crane Technical Paper No. 410, (aka The Flow of Fluids Through Valves, Fittings and Pipe), the flow resistance coefficients for standard tees are:
flow through run ... K = 20 ft
flow through branch ... K = 60 ft

The last term is "Eff sub t" meaning turbulent friction factor. "Eff without the sub tee" means laminar flow.

So in turbulent flow with equal diameters on run and branch, you'll get about 1/3 through the branch and 2/3 through the main run if flow restriction downstream at the run and branch are equal.

In laminar flow, all bets are off because then velocity and viscosity have to be taken into account. In really viscous or low velocity situations, you could get negative pressure at the branch. Or with the right geometry, like in a venturi pump....

The vapor velocity is so low in our columns (on the order of 20 inches per second in 2" pipe) that the flow will tend to be laminar unless we perturb it.

Three pipe diameters is the standard rule of thumb for downstream effects -- it takes that far for big vortices to shed smaller vortices.

A shorter distance would work just fine if the protrusion made a lot of turbulence -- which also means more flow restriction. It's a trade-off.

The other way would be to add a lip (by cutting the tube at 45 degrees) to the takeoff tube that sticks into the column. It would be interesting to see if having the lip down (causing a vortex in the takeoff tube) or the lip up (causing bow-wave turbulence) worked differently. My guess is both would do it more or less the same.

The vortices coming out of the packing have got to be so small that they settle down to laminar flow very quickly. Using mesh, loose felt blankets or screens to smooth turbulent flow to laminar is very common.

http://en.wikipedia.org/wiki/Lewis_Fry_Richardson" onclick="window.open(this.href);return false;" rel="nofollow:
Big whirls have little whirls that feed on their velocity,
and little whirls have lesser whirls and so on to viscosity.
(viscous flow is an old way of saying laminar flow)
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Re: VM Valve question

Post by HookLine » Tue Dec 23, 2008 8:52 pm

Good stuff, Snuffy.
The vortices coming out of the packing have got to be so small that they settle down to laminar flow very quickly.
That is true. But the if the mesh packing comes right up to the bottom lip of the take-off branch, would that be enough turbulence?

It will still take some finite distance for the small scale turbulence to settle, and once there is flow into the take-off branch presumably that would generate some additional turbulence of its own.
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Re: VM Valve question

Post by eternalfrost » Tue Dec 23, 2008 10:23 pm

seems to me the most straight forward way to make the path splitting even is to simply orient the T into a horizontal position. that way each branch will be identical.

the only problem i can see is returning the reflux into the center of the column. my first guess at solving that would be to extend the reflux side into the T with a 45 degree cut on the end. making a triangle trough into the center with a down-turned spout like a Bok.
you could even do the same from the other side on the takeoff arm to keep it symmetrical...

anyways, just a thought, it would only require one additional 90 elbow to get the reflux coil vertical again...

not sure on how much an issue the whole thing is though since mini's head can be cranked below azeotrope, so further splitting into the takeoff arm isnt really necessary...

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Re: VM Valve question

Post by HookLine » Tue Dec 23, 2008 10:58 pm

eternalfrost wrote:seems to me the most straight forward way to make the path splitting even is to simply orient the T into a horizontal position. that way each branch will be identical.
You mean something like this?
T-bar VM head.gif
T-bar VM head.gif (4.91 KiB) Viewed 2245 times
the only problem i can see is returning the reflux into the center of the column. my first guess at solving that would be to extend the reflux side into the T with a 45 degree cut on the end. making a triangle trough into the center with a down-turned spout like a Bok.
you could even do the same from the other side on the takeoff arm to keep it symmetrical...
That problem has been dealt with using just a simple collar at the top of the column, just below the T, like in the drawing above.
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Re: VM Valve question

Post by eternalfrost » Tue Dec 23, 2008 11:46 pm

yup exactly what i was talking about hook.

seems to me that would sidestep the whole theoretical laminar/turbulent issue you guys were talking about.

even though, in a practical sense, it seems the simpler vertical T works just fine as minime has shown.

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Re: VM Valve question

Post by HookLine » Wed Dec 24, 2008 12:00 am

eternalfrost wrote:yup exactly what i was talking about hook.

seems to me that would sidestep the whole theoretical laminar/turbulent issue you guys were talking about.
I agree.
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Re: VM Valve question

Post by rad14701 » Wed Dec 24, 2008 6:42 am

Good stuff, guys... I can see where variations on the VM theme could potentially make a big difference... Might have to dig into some of that theoretical literature Snuffy mentioned... Gonna have some extra free time over the holidays to do some reading...

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Re: VM Valve question

Post by maoule » Wed Dec 24, 2008 7:19 am

I'm trying to get my brain wrapped around what is happening to the vapor when and after it hits the reflux condenser; more specifically, the energy/velocity of the vapor. I understand the vapor condenses and falls back down the column, but, do the alcohols and water condense differently and is there any energy that wants to continue to atmosphere? What effect, if any, does having the reflux tube entirely open (except for the coil) to atmosphere, versus a cap with a vent hole, versus packing stuffed in the opening have on the process?
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Re: VM Valve question

Post by minime » Wed Dec 24, 2008 7:27 am

maoule wrote: What effect, if any, does having the reflux tube entirely open (except for the coil) to atmosphere, versus a cap with a vent hole, versus packing stuffed in the opening have on the process?
I run with my coil wide open to the atmosphere with one wrap of copper gauze. On the last column style I built 3" reduced to 2" the coil is only 6" long and the slight discoloration of the copper gauze from condensing was only on the first couple of inches. There is absolutely no energy being released to the atmosphere save a bit of heat radiating from the waste line of the coil.

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Re: VM Valve question

Post by rad14701 » Wed Dec 24, 2008 7:37 am

maoule wrote:I'm trying to get my brain wrapped around what is happening to the vapor when and after it hits the reflux condenser; more specifically, the energy/velocity of the vapor. I understand the vapor condenses and falls back down the column, but, do the alcohols and water condense differently and is there any energy that wants to continue to atmosphere? What effect, if any, does having the reflux tube entirely open (except for the coil) to atmosphere, versus a cap with a vent hole, versus packing stuffed in the opening have on the process?
Think of it this way, maoule...

The column holds gradient vapors at varying temperatures from bottom to top... The bottom will have more water vapor than the top because water is heavier... The packing catches the water and it works its way back down the column back to the boiler...

Having the reflux condenser at the top is like having an imaginary cap at the top... You supply enough coolant so that no vapors can make it past without condensing and falling back down as reflux... The condenser at the top is working like the bouncer at the front door of a club... Once the club is full to capacity, nobody gets past and is turned away...

Now what you have accomplished is to attain an equilibrium within the column, from bottom to top, where temperatures and vapor densities try to remain stable... With this equilibrium in place the product at the take off point should remain stable in temperature and ABV%, for as long as ethanol remains in the vapor...

So, here we have vapor which is a combination of water and ethanol rushing up the column at approximately 20 inches per second through our packing... We also have the brakes being applied at the top which eventually brings the vapor rise to a complete halt and turns it back as reflux... How far above the T this braking action starts, and how much effect it has on our product take off, is still up for debate... It is, however, in my opinion, an important piece of the puzzle... The distance and volume above the take off point, on up to the condenser, must have some bearing on overall VM performance as it is in this area that the brakes start being applied, so to speak... If the condenser is working too efficiently and returning a lot of reflux then this boundary could theoretically be pushed to or below the take off point... This is why a thermometer at the T is so critical...

Anyway, hope this helps...

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