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Re: calculating heat input

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  • geoff
    Hi, I,m pretty new to this hobby. (2months) I have a homemade 5 gallon (U.K) Boka reflux its only a metre high (39 inches) and 46mm diameter (nearly 2
    Message 1 of 21 , Apr 24 10:22 AM
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      Hi, I,m pretty new to this hobby. (2months) I have a homemade 5 gallon (U.K) Boka reflux its only a metre high (39 inches) and 46mm diameter (nearly 2 inches). The boiler is a 3Kw urn used for making hot drinks (thermostat controlled). From the outset i had to come up with a way of controlling the power input. I just used a triac controller you can get them on e-bay and amazon for about £12 (usd 20) generally from China.With this i have almost infinite adjustment of power input. During the reflux after full on heat up to boil i drop the power to 800Watts which gives me the right velocity for good reflux I get 92% ABV with a 25% take off, as things progress I have to slowly(over 10 hours) turn the watts up to 1600 (ABV drops to 88%) also reducing the take off rate.So what I am saying is that its good to know all the technical heat calcs for the boiling mix, its not necessary to know this (i Didnt) to get acceptable performance. Basically biggest heater you can power from your suppy(fast boil) and a cheap triac controller. Just search on heat input or triac controller.

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    • DarkGreyMatter
      And 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
      Message 2 of 21 , Mar 20
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        And 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'm not!
        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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