44992Re: calculating heat input
- Mar 20, 2014And hidden there, in all that heat input, is a huge indicator of the inefficiency of typical pot-stilling experience:
To get (alcoholic) vapour of any %ABV out of the top of a still, the entire contents of the pot first need to be heated up to BP. Then more heat is needed to vaporise anything you want to travel upwards!
Careful study of Langmuir's Equation (you know, that Nobel Laureate physicist fellow.....) shows that no boiling, at all, is actually necessary if the energy input is properly managed.
But to keep things simple.......let's assume that the output must be condensed (the inverse of boiling) from vapor, so we'll allow that portion of the wash to be considered "boiled" - but not the rest.
(The bulk of the wash merely needs to be raised to boiling point to ensure free evaporation of the desired alcohol molecules, into the vapor phase and out of the liquid phase. All of them.)
Any heat put into the non-alcoholic portion of the wash is ejected as effluent (From stills of ANY design regime) and so is all of the heat energy it contains!
And there's the key...... in a Smart Still, that "waste heat" can be used to preheat the wash up to it's boiling point, so that it is at the ideal (vaporisation) temperature the instant any further heat is applied.
The wisest amongst you all might have by now realised that the only way to get all of the alcohol out of a pot still charge is to heat all of that charge up to the boiling point of water.
Because the boiling point only slowly migrates upwards in a pot still (as the alcohol boils off) this takes considerably, considerably more heat than the idealised minimum according to Langmuir's Equation.
You might be content to assume that such a problem is insurmountable?
I understand Conservation Of Energy and can state, with certainty, that substantial improvements in practical distillation efficiency are achievable.
NB: there is no guarantee that doing this will be a trivial pursuit!
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