Offset condenser questions

rezaxis · Post by **rezaxis** » Tue Nov 21, 2006 6:58 pm

Long post, thanks for reading.

Keg with 2.5" (63mm) column packed with copper mesh, 48" (1.2M) to where the reflux enters the column. 6" (15cm) up from there a 2 x 2 x 2 (50 x 50 x 50mm) tee goes over to the condenser, collection cup. The condenser is 26 turns of 1/4"ID (6mm) copper inside 2.5" (63mm) pipe. The coil is separated enough to keep the coils from touching together, but the gap between turns isn't near equal to the OD of the tube. The coil is separated from the sides of the condenser shell by about 1/2" (13mm) all around. My condenser water is pumped from a picnic cooler with a pump that can be described as over sized. It flows into the top of the condenser and exits the bottom. To make the transition between this 2.5" (63mm) condenser and the 2" (50mm) tee/drop to the collection cup, I made a cone/reducer that allows the vapors to come up through a 3/4" (19mm) hole surrounded by 6 more 1/4" (6mm) holes, this also funnels the condensed vapor down the center of the 2" (50mm) Dia. drop through the tee to the collection cup. The cup is dished at the bottom and the condensate drains at the center where it tee's off, one way back to the column, the other to the output.

A picture would have been so much easier!

I had to get that out of the way so you folks might understand what's happening next: Hope some of you are still with me.

I made a trial run with plain tap water. My condenser will not knock down the amount of vapors I can produce. It can do it at a VERY low flame, but no higher. I also hear a gurgling noise coming from inside the condenser that maybe sounds like condensate hitting a hot surface and re vaporizing!

The output/reflux valves are almost too hot to touch, and the condensate is hot! It kind of drains out unevenly too.

Should I scrap this condenser and go with a completely different design? Would removing several turns of coiled tube, increasing the distance between coils make the rebuilt condenser more efficient even though the tubing length has been shortened? Is my cone that the vapor goes up through and the condensate drip down through the surface that is possibly re vaporising condensate, or could the collection cup area be hot enough to vaporize condensate? Should I lose the holes in the cone and just open it up till it's just a 2.5" (63mm) to 2" (50mm) reducer? Is everybody else with this type of rig have valves and the surrounding part be so hot? Is an even smaller burner the answer? Or scrap this thing and scavenge parts to make a pot still?

I got a wash that's gonna be done in a day or two...

masonjar · Post by **masonjar** » Tue Nov 21, 2006 8:31 pm

For the condensor, you could improve its effectiveness by filling the gaps between the coils and the outer pipe walls with copper mesh.

The gurgling might have something to do with those 1/4" holes. I can't quite picture what this looks like, but those holes sound kind of small for BOTH vapor to ascend and condensate to descend. The 3/4" hole sounds fine to me. My elliptical plate still will gurgle if I turn the heat up too high. In my case, the column literally gets flooded with liquid because when I pulled the thermometer out of its hole, the liquid started pouring out the thermometer hole - even though this was a few inches higher than the top of the packing. Is it possible that the liquid level in your column climbed high enough that the 3/4" hole was submersed?

My distillate was what I would describe as 'very warm', and the needle valves also get 'very warm'. I wrapped my condensor hoses around the take-off line to help cool it off and that worked nicely for me.

rezaxis · Post by **rezaxis** » Tue Nov 21, 2006 9:32 pm

Hey mason jar thanks for the reply. Maybe I can better describe the cone with the holes thing:

Describing it from the top down - It starts with a 2.5 inch copper slip coupling. To the bottom edge on this slip coupling is brazed a shallow cone pointing downward. The cone has a 3/4 inch hole in the center surrounded by 6, 1/4 inch holes. Brazed to the center of this cone is a short length of 2 inch copper pipe, which covers all the holes in the cone. The condenser slips into the top and the bottom slips into the tee coming off the refraction column. The vapors must pass through the holes in the cone on the way up and the condensate must pass through the holes in the cone on the way down.

I'll do another water boil tomorrow with the copper mesh packed in the condenser. I'm leaning toward cutting one big 1 1/2 inch hole in the cone. This would still leave 1/4 inch all around and allow condensate to fall directly into the collection cup without running down the sides and maybe back into the tee branch leading to the column. Might also eliminate the gurgling if it's really caused by vapor/condensate passing each other.

I was able to remove the collection cup and valves while the rig was steaming and with a flashlight I was ALMOST able to see up in there to the cone and see what was happening, but with all the hot water dripping and steam coming out it was getting dangerous and I gave it up.

speedfreaksteve · Post by **speedfreaksteve** » Tue Nov 21, 2006 10:11 pm

Unless I missed something with your design, it seems apparent that the real problem is lack of flow through the 1/4" coil, and possibly a secondary problem of lack of surface area for the vapours to hit the condenser. If you were using 3/8" copper coil then your flow would increase 50%, which should make a huge difference.

rezaxis · Post by **rezaxis** » Wed Nov 22, 2006 8:03 am

Steve,

I get 2.3 GPM through this coil. The temperature difference (delta T) across the coil is barely noticeable, just a degree or two maybe. I can barely feel the difference in temperature with my hands. Leads me to believe that I have enough flow, but I'm not utilizing it efficiently. I would like to see this delta T be more like 6F.

Heat exchanger guys out there feel free to point out any errors in my thinking. The only way I ever learned anything was by screwing up something first!

I think I'm either having a problem with the vapors not contacting the condenser coil efficiently, or maybe I'm just pushing too much vapor into the condenser. I know I can push a lot of vapor through this 2.5" column.

I think I'm going to open up the cone to just leave a drip edge for the condensate to fall directly into the collection cup, and fill the condenser with mesh.

masonjar · Post by **masonjar** » Wed Nov 22, 2006 10:59 am

I strongly believe the mesh will take care of the vapors sneaking around the coil. My coil is only about 10 turns or so. I got 4 feet of 1/4" pipe and the whole thing fits in in the 1.5" column and takes only about 8" of space. My column floods before any vapors leak out. I do have my condensor rather tightly packed with mesh though. I think people have a tendency to over-do their condensors. It takes only a trickle of water to pull the heat out.

rezaxis · Post by **rezaxis** » Wed Nov 22, 2006 2:35 pm

Have you ever measured the difference in temperature of the water entering and the water leaving your condenser?

I know I have way more water flowing through my condenser than I need to. I could throttle the out put of the pump, but it would just cost me more electricity to pump through the restriction. This motor draws 4.5A with no head, but I could run it for a year straight and generate 200+ psig the whole time!

I got the motor and pump for nothing, and like everything else that's just sorta scabbed together from salvaged parts, it's not perfectly suited for the job but it works. So, in this case I got more pump than I need.

And Steve, yeah I would have liked to make the coils in my condenser from 3/8" tubing, but scavenged 1/4" ID soft copper tube is what I had to work with (Try to find 5/16" compression fittings!) So I made it as big as the free piece of tubing would allow me to make it, figuring it would be better to have too much condenser than not enough.

rezaxis · Post by **rezaxis** » Wed Nov 22, 2006 9:03 pm

Well. I just wrapped up my final water run. And I think it was a real success!

I stuffed the condenser with mesh per MasonJars suggestion(I remember reading that on here somewhere too...) I left the holes in the cone alone.

Fired up 10 gallons of water and this thing now knocks down ALL the vapors I can produce! I just left the burner running as fast as it was going when I brought it up to temp and it started running condensate in a steady stream alternating with moments of fast dripping. I collected 4.2 liters of distilled water in 1 hour.

Some other facts gathered: Averaged about 10F differential condenser water temperature. I feel that is very good! My condensate came out at 158F! That's HOT! I expected much cooler. My picnic cooler was filled with 130F water at the end! I'll use ice next time!

And this is prolly the best thing right here: I have 5 seperate slip in connections on this rig. Where a piece of copper pipe slips down into a larger piece of copper pipe with typical slip coupling type tolerances. NONE of these connections passed ANY vapor that I could tell. I wrapped two of the connections with tissue paper and they stayed bone dry the whole time!

And the gurgling... It's coming from the metering valve on the out put! Don't ask me what's happening in there! Ain't got a clue! Would like one though...

masonjar · Post by **masonjar** » Wed Nov 22, 2006 10:08 pm

And the gurgling... It's coming from the metering valve on the out put! Don't ask me what's happening in there! Ain't got a clue! Would like one though...

Is the output line 1/4" pipe also? How long is it?

My output line is 1/4" and about 3 feet long. When I turn the valve so that it is a slow drip, it takes almost a minute for the liquid to move down the long pipe. I wonder if maybe yours allows air bubbles to climb up the output pipe and gurgle through the needle valve or something.

So does your column flood if you go full reflux and blast the heat?

trippvc · Post by **trippvc** » Thu Nov 23, 2006 1:19 am

it's easier to knock down alchol vapor than water anyhow. r

markx · Post by **markx** » Thu Nov 23, 2006 2:41 am

The condensate coming out of a reflux head is always near the boiling point temp......you'll need an additional aftercooler for the takeoff to cool it down to acceptable levels. 2.3GPM is way overkill.....my cooler handles 3kW with under 1 liter per minute. Haven't measured the temp of entering water but it exits with temp being around 55C.

The gurgling occurs when the takeoff valve is wide open and starts sucking in air and condensate alternatively by the pressure drop that the exiting liquids create. I get that too when I run water through the column or open up the valve all the way.

rezaxis · Post by **rezaxis** » Thu Nov 23, 2006 7:31 am

Masonjar: I don't know if my column floods or not, but I don't think so, 'cause if it did it would overflow the collection cup and begin leaking there (that's one of the slipped connections I mentioned earlier.) My take-off is 1/4" OD copper about 3' long.

Markx: Yeah, too much pump, not gonna change it unless I fall into something more appropriate. Thanks for the explanation about the gurgling! I got it. I got a siphon going, that alternately makes and breaks. I'll put a vacuum breaker in the beginning of my output line to solve this. That should even out the exiting stream of condensate. Thanks for turning the lights on for me!

After cooler! Yaugh! I thought I was done with the building part of this project...

markx · Post by **markx** » Thu Nov 23, 2006 1:20 pm

Don't bother with the vacuum breaker......the gurgling is really not a problem and will not occur when normal takeoff rates are applied. Alcohol flows much more evenly compared to water and you should not experience the fluctuating flow with the real stuff.

hornedrhodent · Post by **hornedrhodent** » Fri Nov 24, 2006 9:01 pm

="rezaxis"

After cooler! Yaugh! I thought I was done with the building part of this project...

You'll need the aftercooler if you want to get continuous readings from your alcometer.

rezaxis · Post by **rezaxis** » Fri Nov 24, 2006 9:59 pm

Yeah, mister rhodent, I figured that out tonight when ran my first wash through it without a condensate cooler. My parots beak got to sit on the sidelines.

I found out I can flood my column. I found out I can loose equilibrium, or what ever it's called when I fiddle with the valves too much. I found out I can't figure how to make cuts from smell/taste/feel alone (yet). It all smelled sweet and sort of bad.

I kept checking and waiting for that "sweet" smell to go away and it never did. I collected to 92C and shut it down. It's all split into 400mL portions and I'll play with it tomorrow.

Might mix it all except the first 250mL which I seperated first back into 5 gallons of water and run it again. Try to get a reflux ratio figured out and just let it run without playing with the valves too much.

Anyway, I sure wouldn't have gotten to this point without this forum and the home site, so thanks to all.

hornedrhodent · Post by **hornedrhodent** » Fri Nov 24, 2006 10:20 pm

="rezaxis"I kept checking and waiting for that "sweet" smell to go away and it never did. I collected to 92C and shut it down. It's all split into 400mL portions and I'll play with it tomorrow.

Might mix it all except the first 250mL which I seperated first back into 5 gallons of water and run it again. Try to get a reflux ratio figured out and just let it run without playing with the valves too much.

Yes - checking the small bottles in order the next day when your nose and tongue are fresh is a good idea.
Re-distilling a number of times with a new still is a good idea - you need to learn to drive it.
Diluting it back to brewing strength may help eliminate some of the nasties as well - you could also add some bicarb soda to the pot and see if it does anything to clean up that heads carryover.