Air condenser

[Swag]

I just recently took my still out of mothballs. Pieces were everywhere, but I finally got a basic reflux column going for a batch of sugar wash. It was a chilly day, and I barely had to run any water through the condenser, so it occurred to me that I could accomplish the same thing with air.
I like building things, so I thought I would experiment. I started with the reflux condenser. I used a 1 1/2" copper pipe, 14" long as the base. I attached this to a 2" adapter to fit the top of my column. I also ground off the nibs on the adapter so I could push it through and get more centralized drips back on to the packing.
The way the cooling works is twofold. The air enters in from the top of the ABS enclosure and cools the column. It then exits the enclosure through 1/2" copper pipes running through the column and out through the side of the ABS enclosure. This method affords a lot more surface area for the vapor to come in contact with.
Here's a picture of the column with the pipes running through it:



Here is a picture of the final assembly:



The blower should arrive in the next couple of days. I also have to make an adapter to fit the blower with a tube to feed this thing. Still a work in progress, so I'll update the thread as I go along.
Hell, it may even work....

[Brutal]

Man that's a cool idea! I think it will work but the effectiveness would likely be very dependent on the air inlet temperature. Hope it's not too loud. Love the design of it.

Drinking a Sierra Nevada right now.

[Hound Dog]

I tried way early on to build a air cooled condenser. Not as efficient as your setup. It didn't work worth a damn. I hope to hear your more efficient system works out. It is an inventive idea. Keep us informed either way please.

[InglisHill]

Perhaps what it would lack is a change in temperature gradient over the length of the condenser, one thing water does well. Very interesting. The other thing would be if the air was cold enough you could experience shock cooling, in the isolated places where the tubes are.

Well hell, I am interested to see how you get on

[Brutal]

I remember a post by Bushman of a small micro distillery somewhere that had the most unusual still set up. It had a layed over rotating column, and the condenser was layed back the other way and was just long copper air cooled tubes with shrouds for the air. I zoomed that picture and studied the hell out of it. I think they had a couple of slant plates at the take off. But I'm getting off topic... It's a professional air cooled condenser. Hope Bushy don't mind if I drop his pic in here.

[Swag]

Love the rotating column idea in that pic Brutal, thanks for sharing. Plenty of different ways to skin a cat.
I'm no engineer, but the concept of cooling is fairly basic. You have X amount of heat per unit of time which needs to be displaced. Air is not nearly as good a conductor as water, but that can be compensated for with more surface area and a higher flow rate. Besides, I don't have to take all the heat out of the vapor to cause condensation.

Drinking a Sierra Nevada right now.

Ha! Didn't notice the box in the picture at first. Had plenty of that over the holidays. The Lagunitas Brewery is close to my sons house and we often go there to sample the different brews. I love their IPA.

[shadylane]

Some were in my junk pile is a air-cooled condenser made from 6 ft of finned copper tubing.
I remember on a freezing cold day, it needed a shroud and fan to handle the output from a uninsulated 15.5 keg still with 1375w
The finned tubing came from a base board heater like this.

[Swag]

Any kind of a cooling system needs and adequate flow of coolant to achieve the desired result. Tight cooling fins are great dissipators of heat, yet they still require a focused flow of air across them to remove more heat that they were designed to dissipate. A baseboard heater is relying on convection flow to accomplish this, and is designed accordingly. You would need a specially designed shroud and a high pressure blower to overcome the excessive turbulence and resistance of tightly packed fins, (which are designed for a very slow air velocity across them).
My design is relying on a fairly high rate of flow in a completely enclosed environment. The resistance is low and should be able to pass a fair amount of air through.
That's the theory anyway, we'll have to see how it works.

[still_stirrin]

Well, I am an engineer. And you'll need 30-50 times more airflow (mass flow) than water per degree of temperature difference between the fluids.

The coefficient of conductivity of water to water thru copper is 350-455 W/sq meter per degree Kelvin.
The same for water to air thru copper is only 13.1 W/sq meter per degree Kelvin.
For steam (vapor) to air thru copper is just a little better at 17 W/sq meter per degree Kelvin.

What this says is that the air as the conducting fluid is very innefficient, VERY much so compared to water. So, I hope you have a backup plan to knock down your hot vapors, because I seriously doubt your contraption will be effective enough even at low heat inputs rates.

Good luck. And be safe. You definitely don't want an open flame anywhere near your experiment either. So don't use propane or a stove burner as your boiler heat source.

With an eye of caution here,
ss

[Swag]

Thanks for your response SS. I agree that air is an inferior medium to water, but it does have a rich history of heat transference. Air does a fine job of cooling the engine in our automobiles, as well as transferring the heat from our furnace to our living space.
I figure the air I'm blowing through the condenser is about 100 degrees F cooler than the vapor temperature to start. I'm also using a blower, not a fan, so I can get a fairly high rate of flow. I am also figuring that I don't need to cool the vapor down to room temperature, rather just enough to condense it.
Given the very small volume of water I need to run through my condenser as it is, I think I can easily push 50 times as much air through my contraption.
Anyway, ya never know unless you try.

Cheers!

[shadylane]

Just a thought, A reflux condenser will need a vent on top.

[still_stirrin]

Thanks for your response SS. I agree that air is an inferior medium to water....

It's not an opinion...its physics. You can't wish that away. Have you done any heat transfer analysis?

... I think I can easily push 50 times as much air through my contraption....

50 times as much MASS flow? Bullsh##.

Anyway, ya never know unless you try....

Absolutely don't try it with an open flame. We'll be reading about you in the paper if you do.

I'm completely serious here. Don't gamble on a "hunch" when it comes to highly explosive vapors. DON'T!!!!
ss

[youngonce]

I always wondered if I could use a compressor to squeeze the liquid out of my mash - pressurize the cooler to squeeze the liquid.. sorry off topic..

[Brutal]

Just a thought, A reflux condenser will need a vent on top.

Yes the copper will need a vent on top. I guess an extension that pokes through the shroud is in order. It can't be sealed.

Other thoughts, a blower (leaf blower or similar) will heat the air as it passes through. It will also be as loud as a train.

I am still in support of this experiment.

[Swag]

Thanks for your response SS. I agree that air is an inferior medium to water....

It's not an opinion...its physics. You can't wish that away. Have you done any heat transfer analysis?

... I think I can easily push 50 times as much air through my contraption....

50 times as much MASS flow? Bullsh##.

Anyway, ya never know unless you try....

Absolutely don't try it with an open flame. We'll be reading about you in the paper if you do.

I'm completely serious here. Don't gamble on a "hunch" when it comes to highly explosive vapors. DON'T!!!!
ss

So serious! Don't worry, I'll just be testing it with water. No, I haven't done any heat analysis, I'm just going on intuition here. It's just a curious experiment I'm doing. If it works, great, if not who cares. I enjoy building my hunches to see if they work, that's all. I always learn something anyway...

[Swag]

Just a thought, A reflux condenser will need a vent on top.

??? What am I venting? The air goes in through the top and out the 1/2" copper pipes on the side.

[Brutal]

Just a thought, A reflux condenser will need a vent on top.

??? What am I venting? The air goes in through the top and out the 1/2" copper pipes on the side.

A vent for the vapor path. To allow for expansion and movement of the vapor.

[carbohydratesn]

What are you venting? Alcohol and water vapors, mostly, in case your condenser does not knock them all down - just like with any other reflux column.

Air does a fine job of cooling the engine in our automobiles...

Only when the heat is first pulled away from the engine via radiator fluid...the heat is transferred to your radiator, which has an enormous surface area.

Air cools the radiator, not the engine. The engine is water/fluid-cooled.

Internal combustion engines are often cooled by circulating a liquid called engine coolant through the engine block, where it is heated, then through a radiator where it loses heat to the atmosphere, and then returned to the engine. Engine coolant is usually water-based, but may also be oil.

http://en.wikipedia.org/wiki/Radiator_% ... cooling%29" onclick="window.open(this.href);return false;" rel="nofollow

Please do be careful with this, if you use alcohol be prepared to pull the plug as soon as you hear vapor escaping.

[Hound Dog]

Swag, what kind of takeoff do you have for this? What collects the condensated alcohol to get it out? Is it slant plates like a boka? If that is the case then you need to have a vent because you have to close off your take off to let things reflux and you can't run a closed system as this would build pressure on heating and a vacuum on cooling.

Thinking of this, what do you plan to do for a pruduct condencer? If the system is based on a LM style design your alcohol will be exceptionally hot coming off the still. Probably steaming hot. This is why we use a liebig with a water cooled Boka. If it is a CM or a VM, well you are taking vapor off the column and still need to condense it.

The air cooled condenser at the top of the column is for reflux, this only gets you half way there.

[Swag]

Swag, what kind of takeoff do you have for this? What collects the condensated alcohol to get it out? Is it slant plates like a boka? If that is the case then you need to have a vent because you have to close off your take off to let things reflux and you can't run a closed system as this would build pressure on heating and a vacuum on cooling.

Thinking of this, what do you plan to do for a pruduct condencer? If the system is based on a LM style design your alcohol will be exceptionally hot coming off the still. Probably steaming hot. This is why we use a liebig with a water cooled Boka. If it is a CM or a VM, well you are taking vapor off the column and still need to condense it.

The air cooled condenser at the top of the column is for reflux, this only gets you half way there.

This still will be a VM type, and I presently have a water cooled Liebig for my product condenser. I also have a custom pressure release system of which I will provide a photo of when I get home from work.
Although I haven't been doing this for a while, this will be the fifth still I've built. I worked for a time as the service manager for a company which installed large industrial air compressor and vacuum systems. This gave me a fairly good understanding of air dynamics. It also provided me with lots of scrap copper, which I'm now putting to good use.

[bellybuster]

Im a bit cornfused... with the top of your cooling section closed the still will just build pressure until your vapour management valve is opened(huge safety issue). The vapour will never reach your cooling section without a vent on top. Am I missing something here??

[Swag]

Im a bit cornfused... with the top of your cooling section closed the still will just build pressure until your vapour management valve is opened(huge safety issue). The vapour will never reach your cooling section without a vent on top. Am I missing something here??

If the reflux condenser is doing it's job, it should be able to condense all the vapor produced by the boiler and return it down the column as liquid. This is done during the stabilizing phase when the still is first heating up. After that, the valve to the product condenser is opened up to start condensing vapor. If the reflux condenser is inadequate, and pressure builds up, you do need a vent (which I have) or you can crack the valve to the product condenser to relieve pressure. Also, I do not solder the reflux condenser to the top of the column. In the worse case excessive pressure would simply blow the condenser off.

[bellybuster]

but the vapour needs a vent at the top in order to pass by the reflux condenser, without that you simply have a pressure vessel. Without a low pressure area for the vapour to travel to it simply will not travel. Am I mistaken??
turn the nozzle off on a garden hose, does the water move??
Its quite possible I'm way off on this but......

[Swag]

but the vapour needs a vent at the top in order to pass by the reflux condenser, without that you simply have a pressure vessel. Without a low pressure area for the vapour to travel to it simply will not travel. Am I mistaken??
turn the nozzle off on a garden hose, does the water move??
Its quite possible I'm way off on this but......

I know, it seems a little goofy until you understand it. When vapor condenses to liquid there is a huge reduction in volume. This creates a low pressure area within the condenser, which then draws in more vapor. That's why you can completely shut off the output as long as the reflux condenser is efficient enough to condense all the vapor from the boiler. This is easy enough to achieve with a water fed condenser, and yet to be seen with my contraption.

[bellybuster]

wouldn't you have to have a seriously efficient condenser to pull that off? As the pressure rises in the still, so do the boiling points requiring that much more condensing power to attain full reflux. It would be like chasing your own tail.

Don't get me wrong, Im interested, guess I just don't understand the dynamics fully

[Swag]

Turning the output off is a standard procedure to let the column attain equalibrium before running the product condenser. Some guys do it for an hour or longer. My water fed reflux condenser does it easily. All you're doing is taking the same amount of heat out of the vapor as was put into it, just like the product condenser does. Whatever your heating source expands, the condenser contracts.

[Swag]

In addition to my previous post, the liquid which has been condensed is now flowing back down the column through the packing, further cooling and condensing the up-swelling vapor. This causes the the water in the vapor to condense first, since it has a higher vaporization temperature than the alcohol. This process eventually stratifies the temperature in the column so that the elements within the vapor which have the lowest boiling point are at the top of the column. Then it's harvest time.

[skow69]

If the reflux condenser is inadequate, and pressure builds up, you do need a vent (which I have) or you can crack the valve to the product condenser to relieve pressure. Also, I do not solder the reflux condenser to the top of the column. In the worse case excessive pressure would simply blow the condenser off.

Now I'm confused. Looking at your photo, I see the cooling air is vented, but not the vapor from the boiler. Also, the condenser appears to be soldered.

I think I understand bellybuster's point. At the start, the column and RC are filled with air (not condensable). Normally, vapor produced in the boiler pushes the air out the vent at the top until vapor fills the column and RC and the reflux cycle begins. Without the vent, vapor production will build pressure and the air will compress a bit, but I don't see any reason to believe the vapor will ever get to the condenser.

Turning the output off is a standard procedure to let the column attain equalibrium before running the product condenser. Some guys do it for an hour or longer. My water fed reflux condenser does it easily. All you're doing is taking the same amount of heat out of the vapor as was put into it, just like the product condenser does. Whatever your heating source expands, the condenser contracts.

True enough that in a closed system, once the initial air is evacuated, you could theoretically attain a steady state of vaporization/condensation that balanced exactly and so didn't cause any pressure change. But a volume of liquid expands by a factor of some 1600 when it vaporizes, so it only takes 1 or 2 ml of liquid to fill the entire column with vapor. I don't think you can count on that balance without some very accurate system of measurement and control.

[bellybuster]

Now I'm confused. Looking at your photo, I see the cooling air is vented, but not the vapor from the boiler. Also, the condenser appears to be soldered.

I think I understand bellybuster's point. At the start, the column and RC are filled with air (not condensable). Normally, vapor produced in the boiler pushes the air out the vent at the top until vapor fills the column and RC and the reflux cycle begins. Without the vent, vapor production will build pressure and the air will compress a bit, but I don't see any reason to believe the vapor will ever get to the condenser.

True enough that in a closed system, once the initial air is evacuated, you could theoretically attain a steady state of vaporization/condensation that balanced exactly and so didn't cause any pressure change. But a volume of liquid expands by a factor of some 1600 when it vaporizes, so it only takes 1 or 2 ml of liquid to fill the entire column with vapor. I don't think you can count on that balance without some very accurate system of measurement and control.

exactly what I was sadly attempting to get at. Thanks Skow69

[Tokoroa_Shiner]

I agree with belly and skow. There needs to be a vent at the top of the column. As the still and wash heat up. It will all expand. That needs to go some where.