Yet another condensing coil

[MetalHead]

I'm relatively new to the "profession" and ran into some confusion and challenges making a coil. This information might be helpful to someone in a similar situation.

The goal that I had for my coil was to use easily available components, get things done relatively fast, and get good performance.

Performance:

I went to the calculator in the forum and, for my application, it looked like about 6 ft. of 1/4" OD copper tubing would fit the bill. This calculator is great and easy to use. Very highly recommend it. In my case, since I wasn't too confident of some of the numbers I input, I decided to plan on 8 ft of active coils.

Materials and availability:

I did a little research in that I looked around the local Lowes. I can get up to 2" OD copper tube and related fittings off the shelf. So, I want to use the 2 inch CU tube for the shell of my condenser, meaning that I have to wind my coil pretty tightly to allow the vapor to get around it. I can get down to 1/4 in. CU fittings, same shelf, but...

The small fittings are a bit deceiving. 1/4" CU fittings are really 3/8" OD, and I wanted to build my coil from 1/4" actual OD copper. You can get 1/4" actual OD soft copper tube, but standard 1/4 fittings won't work, they're too big. If you get the 3/8 actual OD copper tube it won't bend in a very tight coil without collapsing. The smaller OD tube is also better for heat transfer.

Just to make clear:
Copper fittings labeled as 1/4", are really 3/8 in OD. From here on out, I'm going to refer to the tube sizes as their actual OD.

What I decided to do was make a parallel flow tube condenser, with two parallel paths, each of 1/4 OD tube. They are joined with a couple of home-made manifolds, providing 3/8 OD tube going into and out of the coil - which are easy to get fittings for.

So here we get it done:

I cut two lengths of 1/4 inch OD tubing to 5 ft each. One end was pinched (Just cut with a pair of dikes). The other end was de-burred and flared, then I made a little funnel with some masking tape. (You can skip the flaring, I had the tool sitting there) Fill the tube with salt, rap along the sides to make sure it fill all the way. Then pinch off the ends. The salt will make forming it easy, and can be flushed out later.

I then marked off 10 inches, and made a 180 degree bend using a 1inch tube for a mandrel, then a 90 degree bend using a tubing bender. This is shown in many posts about making a condenser. Just be sure to bend both of the tubes the same way. This can then be inserted into the 1" od tube:

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This gets us started winding the coil. Just keep things tight and move your way up the 1 inch pipe. Bend one tube at a time, and keep it all compact:

When you have the amount of coils you want, pull it out of the tube, it should look like this:

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Next came the little manifolds, which are made and soldered in place. They can be done with a hacksaw, file, and drill press. Use 1/2 thick brass, and pickel it before soldering:

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Trim the center tubes of the coil and shake out the salt in the straight portion (The rest will be flushed out later) Solder the in-line junction manifold to the tubes coming out of the center of the coil. Solder a length of 3/8 OD tube going out, about 6 inches or so.

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Then do the same with the outer portion of the coil. Cut and trim the two tubes and shake out the salt. There will be some de-burring and filing, be careful not to damage the adjacent coils. Pull the coils apart until they have about 1/8 inch spacing between them. Then solder on the second junction and 3/8 OD tube.

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Now you're almost done. Expand out the rest of the coil so that the tube spacing is about 1/8 inch all the way through. Use a piece of hose and attach one of the 3/8 tubes to a water spigot. Turn it on and the salt will flush out in a couple of minutes. Let it run for awhile and check for leaks. Then back down to the shop to fit it to the outer shell. This assembly should slide into a 2" copper tube without any problem. I did file a chamfer in the 90 degree junction to help center it. Get a 2 inch cap and mark/drill it for the 3/8 tubes. Poke the tubes through and solder in place, then solder the whole cap onto the 2" tube. (Note that I used a brass cap, since I had the material handy)

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I should note here that I probably was too conservative with the overall size. I ended up with 20 wraps using 2 lengths of 5 ft each. You might want to bring the size down a bit. The goal I had was to end up with the 3/8 OD tubes, which are then easy to plumb into the rest of the still using easy-to-get hardware. I also avoided using 3 inch copper tube for the shell, which was hard to come by. I've done a couple of trial runs, and its working well.