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reflux thermometer

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  • povinstitute
    On the offset valved reflux still why put the thermometer at the top of the column as opposed to between the condensor coil and takeoff? Jeff
    Message 1 of 9 , Mar 2, 2007
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      On the offset valved reflux still why put the thermometer at the top
      of the column as opposed to between the condensor coil and takeoff?

      Jeff
    • bbornais
      I suppose you could. The top of the column is convenient, however, and will give you the best readings. The top of the column is removable, allowing different
      Message 2 of 9 , Mar 3, 2007
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        I suppose you could. The top of the column is convenient, however, and
        will give you the best readings. The top of the column is removable,
        allowing different setup if you wish. This is advantageous due to the
        fact that you don't have to drill a hole permanently into your still
        for the probe.

        As long as the probe is not coming into contact with condensed vapour,
        then it will work fine.

        Bryan.
      • Aad Van Roosmalen
        Hoi all Even when the probe is in contact with the condensed vapor it will work fine. the temperature is the same proost Aad ... Mijn Postvak In wordt
        Message 3 of 9 , Mar 3, 2007
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          Hoi all
           
          Even when the probe is in contact with the condensed vapor it will work fine.  the temperature is the same
           
          proost Aad

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        • bbornais
          The temperature of condensed vapour is below the boiling point of the alcohol/water azeotrope. A small amount of contact will probably be negligible, but the
          Message 4 of 9 , Mar 3, 2007
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            The temperature of condensed vapour is below the boiling point of the
            alcohol/water azeotrope. A small amount of contact will probably be
            negligible, but the temperature of condensed vapour is not the same as
            the vapour, or it would not be a liquid.

            Bryan.
          • Harry
            ... the ... be ... same as ... In theory, the temperature of the liquid at the moment it changes phase (collapses) from vapour to liquid, is the same. The
            Message 5 of 9 , Mar 3, 2007
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              --- In Distillers@yahoogroups.com, "bbornais" <bbornais@...> wrote:
              >
              > The temperature of condensed vapour is below the boiling point of
              the
              > alcohol/water azeotrope. A small amount of contact will probably
              be
              > negligible, but the temperature of condensed vapour is not the
              same as
              > the vapour, or it would not be a liquid.
              >
              > Bryan.
              >


              In theory, the temperature of the liquid at the moment it changes
              phase (collapses) from vapour to liquid, is the same. The liquid
              will still be at its boiling point.

              However in practice, most reflux condensers are built for overkill
              (I guess we're scared it won't work). They do the normal job of
              removing the latent heat of vaporization, thus cooling the vapour
              first to a boiling liquid. Then in a lot of cases the liquid thus
              coming off the bottom coils is actually sub-cooled to a point
              somewhat below that.

              This is a prime cause of many of the problems of 'dumping' that are
              discussed. The too-cool reflux liquid has to travel further down
              the column before it begins to reboil, and in some cases it can
              actually dump all the way back to the boiler. Of course this can be
              controlled by a skilled operator, just by slowing down the coolant
              feed.

              Overkill condensers are fine if you take the time to learn how to
              regulate the coolant. If condensers are undersize, they require
              that the heat input is reduced to match the capacity of the
              condenser, or you'll lose vapour, thus product. This of course is
              desirable in VM stills ie partial condensation as reflux, the vapour
              not condensed is harvested for product. On the whole, it is better
              to build a bit over requirements, then use coolant and/or power
              input adjustments , depending on what style of still you have, LM or
              VM.


              Slainte!
              regards Harry
            • bbornais
              My hat is off to you Harry. Bryan.
              Message 6 of 9 , Mar 3, 2007
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                My hat is off to you Harry.

                Bryan.
              • povinstitute
                Where should the thermometer be ideally positioned in an offset head valved reflux sytem if cooling management is also employed? Jeff ... of ... are ... be ...
                Message 7 of 9 , Mar 4, 2007
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                  Where should the thermometer be ideally positioned in an offset head
                  valved reflux sytem if cooling management is also employed?

                  Jeff




                  --- In Distillers@yahoogroups.com, "Harry" <gnikomson2000@...> wrote:
                  >
                  > --- In Distillers@yahoogroups.com, "bbornais" <bbornais@> wrote:
                  > >
                  > > The temperature of condensed vapour is below the boiling point
                  of
                  > the
                  > > alcohol/water azeotrope. A small amount of contact will probably
                  > be
                  > > negligible, but the temperature of condensed vapour is not the
                  > same as
                  > > the vapour, or it would not be a liquid.
                  > >
                  > > Bryan.
                  > >
                  >
                  >
                  > In theory, the temperature of the liquid at the moment it changes
                  > phase (collapses) from vapour to liquid, is the same. The liquid
                  > will still be at its boiling point.
                  >
                  > However in practice, most reflux condensers are built for overkill
                  > (I guess we're scared it won't work). They do the normal job of
                  > removing the latent heat of vaporization, thus cooling the vapour
                  > first to a boiling liquid. Then in a lot of cases the liquid thus
                  > coming off the bottom coils is actually sub-cooled to a point
                  > somewhat below that.
                  >
                  > This is a prime cause of many of the problems of 'dumping' that
                  are
                  > discussed. The too-cool reflux liquid has to travel further down
                  > the column before it begins to reboil, and in some cases it can
                  > actually dump all the way back to the boiler. Of course this can
                  be
                  > controlled by a skilled operator, just by slowing down the coolant
                  > feed.
                  >
                  > Overkill condensers are fine if you take the time to learn how to
                  > regulate the coolant. If condensers are undersize, they require
                  > that the heat input is reduced to match the capacity of the
                  > condenser, or you'll lose vapour, thus product. This of course is
                  > desirable in VM stills ie partial condensation as reflux, the
                  vapour
                  > not condensed is harvested for product. On the whole, it is better
                  > to build a bit over requirements, then use coolant and/or power
                  > input adjustments , depending on what style of still you have, LM
                  or
                  > VM.
                  >
                  >
                  > Slainte!
                  > regards Harry
                  >
                • Aad Van Roosmalen
                  Hoi Bryan, At the boilingpoint of any liquid there can be vapour as well as liquid and hat is just what we use. proost Aad
                  Message 8 of 9 , Mar 6, 2007
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                    Hoi Bryan,
                     
                    At the boilingpoint of any liquid there can be vapour as well as liquid and hat is just what we use.
                     
                    proost Aad
                  • Aad Van Roosmalen
                    Hoi Harry You needs some overkill because you do not want to blow your ethanol into the envirement(attic ro basement). You can see (in a glascondenser) when
                    Message 9 of 9 , Mar 6, 2007
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                      Hoi Harry
                       
                      You needs some overkill because you do not want to blow your ethanol into the envirement(attic ro basement).
                      You can see (in a glascondenser) when you have overkill, then only the bottom part of the condenser will be wet.
                       
                      proost Aad
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