I am in the process of building a still to produce ethanol for fuel purposes.
The vapour cooling part of the still consists of approximately 15 ft of 5/16 inch pipe wound in a loose coil about 50mm external diameter in side a 67mm copper pipe. Water is passed through the coil, and the ethanol vapour rises up around and through the coil, condenses out and drips back down to a collecting funnel and outlet pipe.

What I would like to do is replace the water flow with the cooling side of a domestic refrigerator. I will have to first de gas the unit I wish to use, silver solder up the new pipe work and get the unit re-gassed.
Question is, how to regulate the amount of cooling at the coil so it does not get too cold and ice up to a solid block. This would also be bad, because the very cold ethanol returning to the reflux colomn would upset the temperature balance of the reflux packing.
Could the speed of the pump motor be varied, using phase angle controller/light dimmer type circuit? The cooling needs to be stable, IE pulses of heating/cooling is not desirable, a constant controlled amount of flow of refigerant through the coil is required.
Fianlly can you see any othe r problems? or any other advice

The design of the still unit I am using can be found at
http://hades.itl.net/~npaisnel/alcohol/design.pdf
and the cooling coil
http://hades.itl.net/~npaisnel/alcohol/cooling coil.pdf
although I am using a greater daimeter colomn and copper not glass

Cheers

Neil