Compact Air Condenser

[Swag]

I came across a big old heat sink and thought it might make a good condenser. I'm putting together a stovetop pot still an wanted a small air condenser to go along with it.
The heat sink was 4" x 18" so I cut it in half. I had a couple of fans which I could use for cooling so I set about putting the unit together.



The idea was to build a copper condensing chamber between the two sinks. I had some copper grounding bar that I salvaged from some equipment racks which were in a dumpster. I used that to build the sides of the box.



There were a bunch of tapped holes along the bar, so I drilled them out to 1/8" and hammered some brass rod into the holes to plug them. Then I pinned and soldered the corners to make a nice square box. I also added an input pipe and tapped an exit hole.
I used a couple of sheets of copper for the lids. I soldered one to the frame and then attached them both to the heat sinks using thermal adhesive. Thermal adhesive is designed to transfer heat.



I then assembled the pieces together and clamped on the fans. Here is the input side:



And the output side:



I haven't tested it yet, but I'm confident that the heat sink is plenty capable of doing the job.

Cheers

[yakattack]

Interesting build. Beautiful craftsmanship. You'll have to keep us updated as you use it.

Yak

[shadylane]

I've thought about something similar but never got around to building it.
Just a thought, a bigger outlet would decrease the odds of it plugging.
Keep us posted on how it works

[googe]

Good stuff mate!, looks like you've found your distilling niche . Wonder what it would be like to have a fan on each end, one blowing air through and the other sucking?.

[still_stirrin]

Vanes in the vapor path would increase the contact time and help you with condensation. I would make the horizontal and staggered between top and bottom.
ss

[still_stirrin]

Vanes in the vapor path would increase the contact time and help you with condensation. I would make them horizontal and staggered between top and bottom.
ss

edit: corrected typo.

[just sayin]

I will interested to see how it works. Nice looking rig!

[Swag]

Vanes in the vapor path would increase the contact time and help you with condensation. I would make them horizontal and staggered between top and bottom.
ss

edit: corrected typo.

Good thought. I had a couple of vanes in there, as you can see by the solder residue on the plate in the third picture, but I removed them because they were slightly tilted and prevented a good seal. I may ad some if problems indicate that they would help, or in a future build. I was also thinking a thinner plenum might be more effective, but I went with what I had on hand, The 2 plates are 9"x4" which gives me 72 sq in's of surface, plus the outer edges of the frame. The thing's heavy too.

Cheers

[Swag]

Good stuff mate!, looks like you've found your distilling niche . Wonder what it would be like to have a fan on each end, one blowing air through and the other sucking?.

Thanks for the vote of confidence. I thought of mounting the fans on the ends, and I'm sure it would work. However, you would have to build a cowling to contain the air and mount the fans on. I simply chose easy. In this configuration the fans blow directly down on the heatsink's thick base, which I believe removes the heat a little bit more efficiently.
I have a bunch of sugar wash going right now, so when it's done I'll give this contraption a test run while stripping it.

Cheers

[skow69]

I love your work on air cooling. It's an under-studied area that deserves much more attention than it gets. Nice score on the heatsink. Aluminum extrusions get spendy fast, in my experience. A heatsink can easily become the most expensive part in an electronics project.

Vanes in the vapor path would increase the contact time and help you with condensation. I would make them horizontal and staggered between top and bottom.

+1 the vanes. That would be a cheap and easy way to increase your contact surface area. I think this is probably similar to what ss was referring to.

vanes.jpg (4.45 KiB) Viewed 5116 times

Or, in keeping with our SOP, you could stuff some scrubbies in the box. Any material for droplets to form on would improve efficiency.

Can't wait for the review. Keep up the good work.

Skol,
skow

[still_stirrin]

....That would be a cheap and easy way to increase your contact surface area. I think this is probably similar to what ss was referring to.

Exactly skow.

Increasing the contact area between the vapor and the copper (which will conduct heat to the aluminum fins) will improve heat transfer. Slowing the vapor long enough to transfer the heat, causing condensation in the chamber is the key to this design.

...Or, in keeping with our SOP, you could stuff some scrubbies in the box. Any material for droplets to form on would improve efficiency...

Scrubbies...yes, that's perfect. Well put skow.
ss

[still_stirrin]

...Wonder what it would be like to have a fan on each end, one blowing air through and the other sucking?...

This too.

Swag, if the fans blew along the fins, instead of straight into them, the fans would be more effective at convecting the heat away from the fins. And I'd suggest blowing from the liquid outlet end towards the vapor inlet to help establish a temperature gradient (as much as you can get across the heat sinks).
ss

[bearriver]

Nice experiment.

I'd leave the fans the way they are, which emulates the airflow of heatsinks in electronics.

Baffles or vanes, whichever they are called, would be slick.

[Swag]

I love your work on air cooling. It's an under-studied area that deserves much more attention than it gets. Nice score on the heatsink. Aluminum extrusions get spendy fast, in my experience. A heatsink can easily become the most expensive part in an electronics project.
Skol,
skow

Thanks, I'm an electronic tech by trade and have a lot of heat sinks that I have scavenged off equipment which was being tossed. I can now start putting them to good use.
I understand the thinking behind vanes and scrubbies. However, I believe that if the plenum is sufficiently cooled it will draw vapor in according to the rate of condensation. I use small tubing on the output deliberately to prevent external air from equalizing the pressure in the condenser. The liquid running through the the tube fills the space and prevents air running back up into the condenser.
Nevertheless, the next one I build I'll add some vanes for comparisons sake.

Cheers

[bellybuster]

now this one is slick, curious to see how much wattage it can knock down. Compact and neat.

[carbohydratesn]

Very neat idea! That's a nice lookin', unconventional condenser.

However, I believe that if the plenum is sufficiently cooled it will draw vapor in according to the rate of condensation

Don't forget, the vapor isn't just being drawn in - it's also (well, mostly) being pushed by the vapor behind it, from the boiler.

If the condenser can't 'draw in' all of the vapor that's produced, the rest is just going to push through and go zipping through the condenser.

If the condenser is just an empty box, the vapor will continue to zip right on through, and out of your still. All of the vapor that doesn't come in contact with the sides of the box will escape.

If the condenser has scrubbers or baffles inside, that vapor has a much better chance of condensing before it is able to escape as a gas.

[Boda Getta]

Very nice!

[Swag]

Don't forget, the vapor isn't just being drawn in - it's also (well, mostly) being pushed by the vapor behind it, from the boiler.

If the condenser can't 'draw in' all of the vapor that's produced, the rest is just going to push through and go zipping through the condenser.

If the condenser is just an empty box, the vapor will continue to zip right on through, and out of your still. All of the vapor that doesn't come in contact with the sides of the box will escape.

If the condenser has scrubbers or baffles inside, that vapor has a much better chance of condensing before it is able to escape as a gas.

Lets think about what's happening in the box. The plates attached to the heat sinks are drawing heat from the vapor which comes in contact with them, and condensing that vapor. Condensation on the plates creates a low pressure area adjacent to the plates, which in turn draws more vapor towards them. Scrubbers are not going to accelerate or add to that process unless the scrubbers are somehow cooled (which is not the case). Vanes would help only by drawing heat back into the sinks. Ideally, vapor is not flowing through the condenser, only into it.
That's my theory anyway, but the proof is in the pudding. I have some more fabrication to get done on the pot still, and a small leak to fix in the condenser, but should have some tentative results this weekend. Thanks for everyone's input.

Cheers

[carbohydratesn]

Let's think indeed.

Scrubbers are not going to accelerate or add to that process unless the scrubbers are somehow cooled (which is not the case)

No, that is absolutely the case. They would be cooled by their physical contact with the heatsinks. It would give the heatsinks a much larger surface to condense vapors on. It would allow much more heat to travel from the vapor out to the heatsinks.

Instead of having an empty box full of air, where the only surfaces for vapors to condense on are the flat sides, it would replace some of that useless empty space with metal that could actually serve a purpose and condense more of your vapor.

Give it a shot without scrubbers. See how much vapor is allowed to pass right through it at different levels of boiler power. Then pack it with a few scrubbers and compare.

I can guarantee you that there will be a large difference in performance. With scrubbers or baffles, it will be able to knock down a lot more vapor, and a lot more power. There's a good reason that several top-notch distillers have suggested doing something like this...

[still_stirrin]

+1 carbohydratesn.

The scrubbies will increase "contact time" of the vapors to the heat sink materials, and increase the surface area in common between the vapor and the heat sink. That allows better heat transfer between the fluid and the solids (via conduction) NOT convection, which is heat transfer through a fluid (be it, a liquid or a vapor).

Lengthening the travel path (vanes or baffles) does the same thing....increases the contact surface area AND the contact time.
ss

[Swag]

I still don't buy the scrubbies because they have limited contact area with the sink and actual heat transfer would be poor. Their value in "slowing the flow", or even creating turbulence in this application is questionable in my opinion. Vanes, which are properly attached to the sinks, are a different story. They would have sufficient mass, and solid contact with the sink, in order to provide good conduction.
I can add some vanes easy enough to make SS happy.
I am having a problem keeping the thing sealed. I could only solder one of the plates to the frame. The other one wouldn't solder cleanly because I could only heat it from the outside. Consequently, I made a PTFE gasket which just isn't cutting it no matter how hard I clamp it. It's possible that the edge of the frame isn't perfectly flat and the gasket material is too stiff to fill in the gaps. I do have a small milling machine that I could use to flatten things out. Any suggestions?

[bearriver]

Wrap the PTFE gasket in PTFE tape to make it more compressible. Cheap easy fix.

I think you are underestimating the potential of the scrubbers in a condenser. Both of my condensers can handle a %200 increase in power with scrubbers, compared to without. Food for thought...

"Baffles" or "vanes" would be ideal, albeit tricky. I would make a one piece structure that drops into the frame as a no solder option, not unlike what many dephlegmators utilize.

[Kegg_jam]

I was thinking something like this

[Swag]

Wrap the PTFE gasket in PTFE tape to make it more compressible. Cheap easy fix.

I think you are underestimating the potential of the scrubbers in a condenser. Both of my condensers can handle a %200 increase in power with scrubbers, compared to without. Food for thought...

"Baffles" or "vanes" would be ideal, albeit tricky. I would make a one piece structure that drops into the frame as a no solder option, not unlike what many dephlegmators utilize.

Teflon tape sounds like a good idea, thanks. You may be right about the scrubbies, I haven't made any tests with them so I should probably keep my mouth shut until I do.
I'll screw the baffles directly to the heat sink and interleave them so the vapor has to travel alternately from one sink to the next. That way I don't have to make them fit perfectly between the sinks.

[Hound Dog]

I could see the vanes getting in the way not allowing you to keep the sides flat and in good contact with the heat sinks. Try making them narrower so they go from frame to frame but not side to side. Basically just the opposite as has been drawn. It would force the vapor from side to side as it passed through.

I was skeptical with your last one that turned out to work. I hope this does too. Glad you are trying new things.

[Swag]

I could see the vanes getting in the way not allowing you to keep the sides flat and in good contact with the heat sinks. Try making them narrower so they go from frame to frame but not side to side. Basically just the opposite as has been drawn. It would force the vapor from side to side as it passed through.

I was skeptical with your last one that turned out to work. I hope this does too. Glad you are trying new things.

Thanks, I'm having fun. I was planning on doing pretty much what you mentioned about the vapor path. In fact I did a little work on it today.



You can see how the baffle vanes will slot in. I milled out some notches in each vane so the screw heads would clear, and that they would be long enough to thread into the sink. These particular 4-40 stainless screws were the same length as the vane width, so the notches were the fix. The vanes now hav a very solid connection with the sink which will enable a good transfer of heat
There is a gap between the vanes and the frame for drainage which I stuffed with copper mesh to force more vapor over the vanes while letting liquid pass.

Cheers,

[bearriver]

I'm curious how this condenser will respond to an obstruction, such as bits of grain material.

When do you plan on running it?

[just sayin]

Great solution to the vains! Improved thermal cantact, increased chilled surface area, and turbulence. What more could you ask for?
I am feeling like a nine year old counting off the days to Christmas and his first Red Rider BB Gun... This has been exciting to watch, can't waite to see how many watt this baby will knock down!

[Swag]

I'll be giving it a test run this weekend on the pot still. I have a propane burner which I'll crank up high to see what kind of performance I get. I'll post the results.

Cheers

[NgrainD]

Been thinking a lot lately about condensers. Even have an idea about an air version I've been kicking around. I really like this tho. It's very small and compact. If it works you should call it the "smart condenser."
I wonder tho. Not to be critical, I think you are doing an awesome job. Would thinner material for the veins be more efficient? Seems like it may take quite a bit of effort to extract heat from such thick bars. In other words it seems that a thicker vein might retain more heat than it expelles to the outer sink. Just a thought.
Stay safe, and still well friend.