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Howdy all,
Been lurking and reading for a while now and finally have a question i cant find an answer to with the search feature.
This is my first still and decided on the valved reflux. I'll be using the all 2" adaptation as noted in many posts. My question revolves around the condenser coil. I am thinking of using 3/8' od for the outer coil and 1/4 od for the inner coil. Will this cause any problems with the water such as excessive cavitation or flow speed problems? My thoughts are to use the 3/8 od as the input and the 1/4 as the output, thus limiting the internal cavitation but it will increase the water pressure.
Should i scrap this and just roll a 1/4" od double helix?
The reason for wanting the 2 different sizes is the gain in surface area of the 3/8" od over the 1/4" but i cant roll a double helix of just 3/8" and get in the 2" pipe. That 50% (roughly) gain in surface area from 1/4" to 3/8" is too tempting not to try hard to find a way of using it.
Is this a bad idea? has anyone done this and was the effect beneficial?
Any and all input is welcome. If this has been covered and i didnt find it, then by all means, flame away
Thanks
Drum

Use 1/4" for both the inner and outer coils. You will get much more surface area for heat exchange than if you use 3/8", AND a better ratio of coolant volume to heat exchange surface area.

just go with 1/4"

my 1/4" single coil works just fine.. just stuff a little scrubber in the top to slow down the vapor.

Another vote for all 1/4 inch.

I would stick with the 1/4"
You even have to wind that fairly tight to get a double coil in a 2" column.

Thank you for the advice. 1/4" it is. Ended up using a 5/16" wooden dowel to wrap the inner coil and a 1.25" wooden dowel to wrap the outer coil. Used one of my 3/8" coil mistakes (and there are many) to fashion a coupler that i'll get soldered up tomorrow. Overall length is 16" with 30' of 1/4" copper tube. Final overall diameter is 1.793" at the widest. So basically i get a tenth of an inch on each side when it is mounted.
Filling the tubes with salt was the best thing i could have done. I started without doing that as it really seemed like an unnecessary step but i couldnt have been more wrong. Once i started using salt, i only had one more problem. Evidently i missed an air pocket and it went flat almost at the end so i had to go get more copper.

Here are some pics of the final go 'round with the tubing.

Pretty good job, and good that you have a decent space between successive turns on each coil. Although the 16" length is overkill for a 2" column. Half that length is enough.