Home Distillation of Alcohol (Homemade Alcohol to Drink)
Calculation of Condenser Size
Theres quite a few variables involved, so its hard to cover
every situation.
You have to consider how hot the vapour is, what its composition
is (eg water takes 3x as much cooling to condense than ethanol),
how cold the cooling water is & how hot its going to get, and how
well the cooling water is flowing around the tube, then even stuff
like if the tubes are vertical or horizontal.
There are very detailed equations about that let you work
this out precisely . But you can also use a few simplifying
guesses to sorta give an idea of what size it could be, for far
less effort. The results may not be quite as accurate, but they'll
give you an approximate idea of what size is involved (so to
be safe/certain you might even just double them !)
The hardest bit is the"heat transfer coefficient". This
descibes whats going on inside & outside the cooling coil or tube,
as well as the heat transfer properties of the tube (eg plastic vs
copper). Rather than doing all the calculations, we can use a
"typical" value. For "organics" being condensed using water in
a shell heat exchanger, this value can be typically 700-1000 W/m2C.
Lets use 850. This is for industrial condensors, where the cooling
water will be flowing past the tube at a fairly good velocity. For
the situation where the cooling coil is just sitting in a big tub of
water (and nothing is stirring the water), this value will be more
like 100-200 W/m2C (lets use 150 W/m2C).
Just remember that the size of the pot is irrelevent.
Its the heating element we need to match.
If you have a "reflux" condensor somewhere in your still as
well, this will be taking out some of the heat too. Subtract
away the amount of heat used there, from the total. So then your
distillate condensor might not be as big in that situation.
Note that you don't need such a long condenser if you keep the outlet temperature
of the water cold. But then the flowrate of water needed increases. Yours to choose.
If you're going for the "coil in a tub" approx, the "cooling water outlet temperature" refers
to how how the tub would typically get to at the end of the run. The maths isn't strictly true,
but should do as a bit of a guess. You can multiply the flowrate by how long you'd be running
the still for in order to work out how much water the tub would need to hold.
As always, they're only as accurate as the guesses used, and
the guesses I've shown above in the examples might not match your
situation in practice. But doing this should give you a basic
starting point from which to experiment. If in doubt, double the
size you estimate, and you should be OK (though your pocket a little
bit lighter).