Bare copper tubing ambient air cooled condenser. Can do?

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rezaxis
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Bare copper tubing ambient air cooled condenser. Can do?

Post by rezaxis » Thu Jan 10, 2008 9:50 pm

I can lay my hands on 50' of 5/8" (1/2" ID) refrigeration copper and 30' of 3/4" (5/8" ID) refrigeration copper. Both unused and sealed and still in boxes, for scrap prices.

I have seen photos of a spiral still and Pints fan cooled condenser. Has any one successfully made an ambient air cooled condenser using bare copper tubing, that can keep up with a 15 gallon keg boiler and gas heat? I've seen the finned tube stuff and that's not where this is going.

I picture the 3/4" being used on the way up and then the 5/8" being used on the way down, with the 3/4" spiraling up, say in about a 10" in diameter coil and the 5/8" spiraling down around the upwards spiral with maybe a 14" diameter coil. Does my description make sense?

I would like to eliminate condenser water and pumps and the use of fans. I'll have to put some sort of pressure relief on my boiler for safety, but the main questions are: Is this a sound idea and is this enough copper to support this size rig?

I saw a Bokabob design that just has a single coil spiraling up and is open at the top, with condensate leaving as it drips back down the coil and before it re-enters the boiler. This looks good because of the open nature of the coil, but the condensate will come out hot and I don't like that.

Even at scrap prices this isn't going to be cheap and I don't want to muck it up, or worse, build something that just isn't going to work. Any experience out there?
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HookLine
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Post by HookLine » Thu Jan 10, 2008 10:28 pm

Nice find on the copper.

As to the design options, I don't think the laws of physics allow too many options.

The only possibilities I can add to the ones you have already listed are:

1. Hang a damp cloth on the condenser tubing, and re-wet it frequently.

2. Make the condenser longer.

Using a fan seriously increases the cooling efficiency, at very little extra up front or running cost. Why don't you want to use one?
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Post by new_moonshiner » Fri Jan 11, 2008 5:28 am

Some things there is just no doing without.. and water to cool a still is one of those .. with very few exceptions.

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Post by Dnderhead » Fri Jan 11, 2008 6:20 am

Ambient air condenser could be made but it mite have to be
exceedingly long

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Post by DestructoMutt » Fri Jan 11, 2008 1:46 pm

80 feet of tubing....define your version of sound. yes, you can make it work. the compromises/trade-offs might not make it worthwhile for most people, but they may be ok for you. increased run times, inefficient use of fuel...

i believe the "spiral tube stills" work because of the low volume of vapor produced by their heaters. with the low vapor flow, the size of the tube is actually sized appropriately. i believe the shape of the tube (an upward spiral) is more for looks and/or space limitations than for physical design properties.

increased vapor flow in an upward spiral might cause "choking". however, a downsloping spiral/coil might work; depending upon the amount of heat input.

non-moving air is a poor heat sink, it is such a poor performing heat sink that it is classified as an excellent insulator. water though, can hold lots of heat and can transfer it between objects quite efficiently.

what type of a still are you designing? why no water?

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Post by absinthe » Fri Jan 11, 2008 5:13 pm

you could use convection to help cool the coil...

so have the coil encased in a bucket or similar with a smaller one inside make sure you have the outer one lifted higher than the inner one so that air can enter the system at the bottom..

now on the top of the otter bucket you want a chimney it will need to be at least a few feet tall i would think to get a good convection current

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Post by HookLine » Fri Jan 11, 2008 5:40 pm

DestrutoMutt wrote:i believe the shape of the tube (an upward spiral) is more for looks and/or space limitations than for physical design properties.
The upward section of the spiral is the reflux part of the condenser. It is actually an important part of the design, definitely not just there for looks.
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Post by DestructoMutt » Fri Jan 11, 2008 5:51 pm

hookline is correct, however, i was talking about the arrangement of the tubing. instead of having a straight column that was 10ft/3m tall, a person would coil/spiral their column up and then use another spiral down for the cooling coil (again in lieu of a straight run).

but that assumes we are talking about a column still or goose neck alembic as opposed to a true pot still.

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Post by HookLine » Fri Jan 11, 2008 5:59 pm

Fair point, I think we are both correct. The spiral shape itself is definitely for space-saving, and maximising cooling surface area.
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Post by rezaxis » Fri Jan 11, 2008 6:47 pm

Sorry I ain't been on here, and thanks for the replies.


I don't want to use fans 'cause they make noise. I don't to use water because it costs me money to run water down the drain. And if I recirculate then I have to run a pump and that makes noise.

80' foot of tubing is a loooong stretch. I picture it stacked up beginning about 2' above the boiler. Maybe I should consider putting it off to the side to eliminate heat rising from the gas flame under the boiler.

I would like to keep the running footprint of this thing as small as possible.

I like the chimney idea, but it might be beyond my scrounging and fabricating abilities. I think there would be a natural convection type of situation set up by just having the coils of copper running around one on top of the other. The heat rising from the bottom one moving air across the next and so on, and all of that helping to draw cool air up.

I don't think I'm ever gonna be anything but a pot stiller. I'm beginning to imagine difficulties controlling the amount of reflux with this thing. It would be interesting to see how this thing would stabilize and what percentage would come off.

I can't afford to build it twice though, so I gotta really sort it out good before I start and that's where all your comments, observations, ideas and warnings are very helpful to me. I encourage you to bring more of the same to this topic. Thanks.
Rez
Last edited by rezaxis on Fri Jan 11, 2008 7:21 pm, edited 1 time in total.
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Post by jjnorcal » Fri Jan 11, 2008 6:55 pm

rezaxis wrote:And if I recirculate then I have to run a pump and that makes noise.
My pond pump, which I got from HD, is about the size of my hand, delivers more than enough water to my bucket, runs essentially dead silent, and cost about $16, if I recall.

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Post by rezaxis » Fri Jan 11, 2008 7:09 pm

I got to admit I've done little serious thinking on this before I posted and I've thought of another detail since my last post.

Lets call the inside coil the reflux coil and the outside coil the condenser coil.

The reflux coil would have a fixed ability to cool vapors dependent upon ambient temperatures. If the reflux coil was big enough and not enough heat applied, there might be no vapor speed left at the turn to enter the condenser coil. Too little heat applied and none of the vapors would travel over to the condenser coil. All of the vapors would be condensed in the reflux coil and return to the boiler. Too much heat applied could cause a potentially dangerous, tube plugging puke and might also cause vapor to escape the end of the condenser coil. Huffing might occur. Accurate flame control would be key to operating this thing.

A too big reflux coil could be made, although given the inefficiency of bare copper tubing to sink heat to ambient air, I doubt it. Too small on the other hand would equal slow. And I don't like slow.

Hmmm,

Rez
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Post by rezaxis » Fri Jan 11, 2008 7:17 pm

jjnorcal, I was typing while you were posting. I've been using a carbonator pump and a 1/3 HP motor the size of my head. It makes noise, and uses the juice. I'm just trying see a no fuss solution to all the tanks and hoses and pumps and fans and etc. in this if I can make it work. I haven't bought the copper yet and I don't have to. It's not going anywhere.
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Post by HookLine » Fri Jan 11, 2008 7:17 pm

Fans do not have to run real hard (ie noisy) to be very effective.

If you wind a spiral air condenser in a conical shape, instead of a straight cylinder shape, you will get much better convection cooling.
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Post by rezaxis » Fri Jan 11, 2008 7:23 pm

I suppose I could just make an eighty foot long condenser coil! That would be a pot still then! I've thought of the cone shape coils to eliminate rising hot air from the coil below. I think that's a good idea too.
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Post by stoker » Fri Jan 11, 2008 11:34 pm

what's wrong with a coil in a drum?
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Post by Old_Blue » Sat Jan 12, 2008 5:12 am

rezaxis,

I ain't trying to be overly critical but I'm sure what you're trying to do has been tried a thousand times over the past thousand years. If it was that efficient or worked that well, 99.999999% of distillation equipment wouldn't be using some type of liquid as a heat exchange medium today.
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Post by DestructoMutt » Sat Jan 12, 2008 12:39 pm

if you are just interested in a pot still type set up, then an 80 foot condensing coil is the way to go.

where will you be setting up? i am assuming outside due to the gas rig and the size of the keg/pot. are you an apartment/condo dweller with limited outdoor space (patio)? closely packed or townhouse/brownstone/ type attched housing? nosy neighbors? law enforcement neighbors?

some vague details would help with this solution required situation.

for instance: a rain barrel makes a convincing cover story for a barrel that can be used to conceal you condensor coil - especially if you do hook it up to your downspout and "forget" to empty the barrel onto your garden during the dry season.

the pond pump i use to recirculate my water is extremely quiet, especially when at the bttom of a 220l/55gal drum full of water. the return hose is draped over a towel so there is no gurgle of return water. my liebig is 20 feet long, but coiled. (the coiling eliminated two potential problems - space used and laminar flow of the vapor and of the cooling liquid (turbulence in the path of each increases the heat transfer).)

so please, more info...one can only do so many sudoku puzzles before they become boring, and crossword puzzles become repetitive after awhile...

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Post by HookLine » Sat Jan 12, 2008 3:37 pm

DestrutoMutt wrote:my liebig is 20 feet long, but coiled.
You have a 20' coiled Liebig? :shock: I would love to see a photo of that, plus an explanation of how you made it.
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Post by absinthe » Sat Jan 12, 2008 3:52 pm

id say he has a copper coil with a rubber hose over top i have seen them used as wort chillers for full grain beer making
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Post by HookLine » Sat Jan 12, 2008 4:11 pm

Ahh, yes, silly me. Sorry, DestrutoMutt, wasn't thinking first thing on a Sunday morning. Probably should go back to bed for another hour or two. :wink:
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Post by DestructoMutt » Sat Jan 12, 2008 7:37 pm

absinthe is correct.

it keeps up with a 3800w heating element in a sanke keg/pot still (goose neck) at full power (240v).

no huffing and puffing, no srubber stuffed inside like with the original liebig i had.

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