Except for those in the electronic business, everyone knows what a condenser is. It's a device that cools down whatever vapors that flow through it to the point where the vapors condense into a liquid. That liquid is what the rest of the still is all about. In the still we are building, it is also the heart of the cooling system.
Condensers can be designed in many ways, but for a lot of reasons, as you'll see in the next paragraphs, a jacketed core condenser is particularly well suited for this still. With jacketed condensers, a circulating and cooling water supply runs between the jacket and the core. This condenses the liquids contained in the hot vapors coming from the column and going through the core.
Here's a sketch of what the insides of the condenser look like:
Simple as it might seem, there are a lot of considerations behind making a proper condenser for the kind of column we want to build.
Most low capacity distillation devices use a small capacity condenser. This is because they are designed for only one purpose: to drop the temperature of the distillation vapor to the point where the liquid separates out of the vapor. That usually does not require a great deal of cooling. Pot stills sometimes just use a coil of tubing that cools the vapor by just exposing it to the surrounding air temperature.
But keep in mind we are building a reflux still. That is a more sophisticated design. In the course of its operation, the reflux still produces a much higher quality of distillate than the pot stills because it effectively re-distills the mixture many times before it is drawn off from the still. That of course, requires much more cooling and much better temperature control than the simpler pot stills.
So, to accommodate these needs, we've designed this still with a much larger cooling capacity incorporated into the condenser. We've done that because we need not only the cooling required to condense the distillate vapors, but also to carefully regulate and control the temperatures inside the reflux tower.
To properly utilize the extra cooling capacity, we've made the water supply and drain lines from V2" copper pipe and run these cooling lines through the reflux column as part of the normal cooling circulation. The primary purpose of these lines is to control the amount of re-distillation (reflux) that occurs inside of the column.
In the sketch shown below you can see that the input cooling water is circulated first through the bottom of the column, then through the condenser, and finally back through the top of the column again.
The rather large surface area of the copper jacket of this condenser acts as a radiator. It dissipates the heat conducted both by the lower input cooling pipe and the heat absorbed from the column vapors by the water as it passes through the column on its way to the condenser.
Those are the reasons why the big, jacketed condenser we are going to build for this job is better. Its also happens to be easier to fabricate and more efficient than those condensers which use a coiled tube contained within the distillate output pipe.
The first step in building the condenser is to fabricate the core assembly.
The Condenser Core
Here's a drawing of what we want to make first. It's the condenser core. It's made from only three pieces:
To make the core you begin by soldering together a IV2" X 1" reducing coupling to a 23" length of 1" pipe. Be sure to clean the fittings and pipe with sandpaper or a stiff wire brush so it shines. Then brush on some flux to both pieces, and use lead-free solder. When you heat the joint enough with a torch, the solder will be sucked up into the joint. While the solder is still runny looking and shiny, wipe the joint with a clean rag. Makes a nice finish on the joint. Then solder a 1" X V2" reducing coupling on the other end in the same way. When you get done, it'll look like this:
The next step is to build a jacket that fits closely around the core. That will allow a thin, fast moving, layer of water with a lot of surface area to circulate around the core, and quickly absorb the heat. In turn, it also allows the condensation rate (both internal and external) to react as quickly as possible to changes in the water flow.
Since the column output is made of 1 V2" piping, we have to reduce this down to 1" piping for the core (above), and then make the jacket out of 1 V2" pipe. That will leave a W space surrounding the core for the water to circulate. To do this, we have to do some strange things to the end caps of the jacket, so that it will match the underlying core plumbing. Here's what's involved:
One cap has a 1 1/8" hole drilled in the end, the other cap, a 5/8" hole. The hardest part is to cut the right size holes in the caps so they will fit nicely with the core.
When the caps are done, you have to cut two nipples of 1 V2" pipe each 2 V2" long, and a piece 23 V2" long for the main jacket. When you assemble the jacket, the V2" reducing tee outlets should be 18 V2" on center. This is not a critical length, but later on you will see that it is important to insure that the cooling tube holes in the reflux column match this dimension.
The more important dimension is the overall jacket length. When the core is placed inside the assembly, it should fit snugly at both the top and bottom caps. You can adjust the length of either one of the nipple fittings (before you solder them) to make any fine adjustments.
Now you can complete the assembly by putting the core assembly through the holes in the jacket end caps, making sure the Tee's are centered along the length, and soldering all the joints. The core and jacket should look like this just before putting them together.
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