Building a Tube in Tube Condenser



Plumbers Delight tube in tube condenserThere are lots of ways to build a condenser. The simplest is a coil of copper in a bucket of water. Here we build the "Plumber's Delight". It is the condenser most often used with the GL 1 day process. It is a copper tube in tube condenser. The methanol vapors will be inside the inner tube and the cooling water will be between the inner and outer tubes. They are often 6 to 10 feet long, but due to the recent high price on copper, we only going to make ours 5 feet long. The longer the condenser the faster it will remove the methanol from the biodiesel.

I've done a bit of scrounging and will use some copper I already have laying around. The inner copper tubing should really be 1/2" soft copper and the outer tube should be 3/4" rigid copper tubing. Since I have a roll of 3/8" soft copper tubing and a stick of 3/4" rigid on hand, that's what I'm going to use.

Close up of the ends of a tube in tube copper condenser

3/4" x 1/2" x 1/2" Tees can be found in the big box hardware stores. We'll use that on the ends of our Plumbers Delight. Since we have substituted 3/8" soft copper for the normal 1/2" soft copper we also need a couple of 1/2" x 3/8" reducers.

Copper fittings have a stop built into them either they are little dimples or they have a ridge going all round the end of the fitting. You want the ones with dimples.  You will have to file them out so your inner tube can slide all the way through the reducer. In my case it will be the 1/2" x 3/8" reducer and in your case it will be the 3/4" x 1/2" x 1/2" TEE.

The soft copper tubing will need to be several feet longer than the rigid outer tubing to make it work easier. For the part that is inside the rigid tubing we are going to crimp the copper at 3 to 6 inch intervals with alternating crimps 90 degrees apart. You do not want to close it completely. You do want to leave about 1/16 of an inch gap. To get the crimps consistent, use a pair of vise grips and scrap of tubing to get the depth of the crimp just right. The crimps are to break up the laminar flow of the inner tube so more of the methanol vapors make surface contact with the inner copper tube. This improves the overall efficiency of the condenser.

Plumbers Delight with Crimps

All that's left is to solder up our Plumbers Delight. Be sure to use lead free solder. When your finished it should look like this:

Plumbers Delight with Crimps
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