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Re: [Distillers] Re: condensor

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  • Robert Thomas
    ... ... How s that snipping for efficient use of bandwidth! Anyway, I have seen things that look like archimedes screws that insert into pipe
    Message 1 of 16 , Apr 5, 2007
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      --- Harry <gnikomson2000@...> wrote:

      <snip>

      > 5. Turbulence.

      <snip>

      How's that snipping for efficient use of bandwidth!
      Anyway,
      I have seen things that look like archimedes screws that insert into
      pipe work. They are induced to rotate by the flow, and hence actually
      break up the laminar pattern of flow further on.
      Now I'd guess this wouldn't work with vapour (at least not on our
      scale/vapour speed/volumes), but how about a fan at the top of a liebig
      blowing down? (not the cold finger design being talked about though).

      Just thinking out loud really.
      Cheers
      Rob.
      p.s. Happy Easter Everyone! Remember, rum and chocolate go well
      together!


      Cheers,
      Rob.



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    • sn_cur
      Not a physicist, but I am pretty sure that the optimal arrangement is a balance between turbulence and laminar flow. Maximising laminar flow reduces heat
      Message 2 of 16 , Apr 5, 2007
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        Not a physicist, but I am pretty sure that the optimal arrangement is a balance between
        turbulence and laminar flow. Maximising laminar flow reduces heat exchange efficiency.
        Maximising turbulence impedes coolant and/or vapour flow.

        Cheers
      • Trid
        ... Turbulence is related to flowrate. The greater the vapor speed will affect the turbulence, even through a parallel path. However, I like the mesh idea in
        Message 3 of 16 , Apr 5, 2007
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          --- Harry <gnikomson2000@...> wrote:
          > 5. Turbulence. Either or both of the fluids being turbulent is more
          > efficient. Commonly it is accomplished by making sure there is
          > something in the pathway of the vapour to force it to divert into
          > the walls of the coolant carrier. It's automatic with coils as they
          > are at rightangles to the vapour flowpath, and providing you put
          > something in the centre space (like mesh) there's full turbulence.

          Turbulence is related to flowrate. The greater the vapor speed will affect the
          turbulence, even through a parallel path. However, I like the mesh idea in
          that it not only makes for the turbulent flow, but the contact with the heat
          transfer surface effectively increases the surface area by means of conduction.

          > There's no such diversion in the proposed design, hence only the
          > edges of the vapours contact the copper transfer walls, leaving the
          > middle of the vapour to continue on (it's laminar flow, not
          > turbulent). You 'may' get some turbulence with the descending
          > condensate using the same path.

          In all fluid flow through a parallel path, there is the laminar boundary layer
          at the edges where the fluid contacts the surface, but the ratio of laminar to
          turbulent flow is proportional to the speed of the fluid...in our case, using
          vapor as that fluid. However, in a case where there is a phase change, I think
          it invalidates the laminar boundary layer as the density rapidly changes
          creating a vacuum where that laminar layer would exist...I think. Thus, I
          think the phase change would affect more turbulence than the droplets of
          condensate in the vapor path.

          > You 'may' also get some hold-up of
          > liquid in the condenser which could lead to problems. It's really
          > a 'try it & see' situation (IOW, experiment). :)

          I suspect liquid 'hold-up' might be more of a factor proportional to how
          tightly packed the mesh would be.

          > 6. Flow direction. There's 3 basic types of condenser: Co-current
          > (same direction of flow for both fluids), Counter-current (opposite
          > directions, considered the most efficient of all) and Cross-current
          > (fluids travel at rightangles to each other).
          >
          > In reality, most condensers are a combination of these. For
          > instance the proposed design has both co-current and counter-
          > current, therefore it's known as a multi-pass condenser (2 passes in
          > this case).

          Regardless of the flow direction, this design is a multi pass because it passes
          through the two sections in series as opposed to in parallel. In light of
          that, designing it as a single pass i.e. where the water is pumped into the
          inner and outer pipes simultaneously as opposed to one after the other, it
          could be more efficient. However, depending on the flowrate, that difference
          could be negligible.

          > Coils are both crossflow (rightangles) and either co- or counter-
          > current, depending on which way you feed the coolant, top or bottom
          > coil.
          >
          > Crossflows are most useful in high-volume and phase-change
          > situations, like steam recovery and our little application.
          >
          > If you consider all of the above you will see why Liebig-style
          > condensers need to be so big or long. No turbulence is the culprit.

          They also have a poor surface area to length ratio. For example, a Liebig with
          a 1/2" inner pipe and a 24" water jacket has 37.7 sq.in. heat transfer surface.
          I have a counter-flow shotgun with 14 tubes with 1/4" id (think big, fat
          Liebig with multiple tubes on the inside) and at only 12" long, has a surface
          area of 132 sq.in.
          The up-side: Liebigs are very easy to clean.

          Trid
          -really digging the idea of the cold-finger...condenser, you sick little monkeys!!!
        • Trid
          ... Actually, no...turbulence is quite desirable. It s also a factor of flow, not an impediment. The greater the flow, the greater the turbulence and the
          Message 4 of 16 , Apr 5, 2007
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            --- sn_cur <sn_cur@...> wrote:

            > Not a physicist, but I am pretty sure that the optimal arrangement is a
            > balance between
            > turbulence and laminar flow. Maximising laminar flow reduces heat exchange
            > efficiency.
            > Maximising turbulence impedes coolant and/or vapour flow.

            Actually, no...turbulence is quite desirable. It's also a factor of flow, not
            an impediment. The greater the flow, the greater the turbulence and the less
            laminar flow. Turbulence is desirable because of the mixing effect in the
            fluid where heat transfer is occurring.

            However, in dealing with situations where a phase change occurs...vapor to
            liquid in our case, we want more than just gross heat exchange. In our
            coolant, pump like mad...the greater the flow, the better. There's the
            turbulence in the coolant that makes it a more efficient heat transfer medium.
            On the vapor side, however, if we raise the flowrate, i.e. vapor speed, too
            much, then there isn't enough time spent in contact with the heat transfer
            surface to affect sufficient heat transfer for condensation to occur. Overall,
            there will be a greater magnitude of energy (in the form of heat) transferred
            from the vapor to the liquid...that's not what we're after. We're not making
            water heaters. Thus, the balance becomes one of heat input to condenser
            capacity. But what we're broaching now is the geometry of the rig as a
            whole...the power of the heat input, the size (i.d.) of the column, the area of
            the vapor space within the condenser, the flow characteristics of the vapor
            path through the condenser, the same regarding the coolant through the
            condenser, the relative paths of each, the physical size, the temperature of
            the coolant, the flow of the coolant...yadda, yadda, yadda.
            ...then combine all of this with the simple fact that we, at home, can only
            construct something *so* elaborate without resorting to a full blown machine
            shop (not that some of us don't fantasize :) ).

            It can be enough to make one scrap it and grab a bottle of Jack from the store
            to make the voices stop :)

            Trid
            -geek
          • sn_cur
            Thanks for your considered and interesting responses, Trid ... The greater the flow, the greater the turbulence and the less laminar flow. Turbulence is
            Message 5 of 16 , Apr 5, 2007
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              Thanks for your considered and interesting responses, Trid

              >Actually, no...turbulence is quite desirable. It's also a factor of flow, not an impediment.
              The greater the flow, the greater the turbulence and the less laminar flow. Turbulence is
              desirable because of the mixing effect in the fluid where heat transfer is occurring.

              I agree that a fair bit of turbulence is highly desirable, for the mixing effect. But
              presumably there has to be a limit to the amount of turbulence before it starts introducing
              resistance to flow. As I understand it, minimising (or at least controlling) turbulence is one
              of the main aims in designing large fluid delivery pipes, because turbulence (or at least
              uncontrolled and excessive turbulence) increases pumping costs, and the size of the pipe
              needed. Although at the flow rates used in stills it may not be an important factor.

              Actually, it is even more complicated than that, because I think the aim is to generate a
              small controlled turbulence layer at the interface between the fluid and the container
              (pipe), because that reduces friction there. But the central bulk of the fluid should be
              relatively turbulence free. I think that is also the way ship hull design is moving, smooth
              surfaces are out and special (geometrically regular) roughened ones are in these days. The
              idea came from shark skin.

              >However, in a case where there is a phase change, I think it invalidates the laminar
              boundary layer as the density rapidly changes

              The dynamic density changes (phase state changes) seem to me a very important factor in
              figuring out the behaviour of condensing heat exchangers. The phase state changes alone
              will introduce turbulence, and maybe that is all that is needed.

              It seems to me that it is a question of the amount and location of the turbulence, not
              simply of maximising overall turbulence.

              Like I said, I am no physicist, and we are getting into some serious physics here, the
              interaction between thermodynamics and fluid dynamics. Love it, but can't say I
              understand it real well. I could be wrong about this stuff.

              >It can be enough to make one scrap it and grab a bottle of Jack from the store to make
              the voices stop :)

              LMAO! Please, Doctor, make the voices go away! Don't worry son, just take these special
              pills, fire up your still, and start swilling.

              And it is getting pretty damn late here, so good night.

              Cheers
            • Robert Hubble
              Trid, Comments inline Zymurgy Bob, a simple potstiller ... That s what I hope I m addressing in my modified Liebig design. The last 1/4 or so of the 1/2
              Message 6 of 16 , Apr 5, 2007
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                Trid,

                Comments inline

                Zymurgy Bob, a simple potstiller





                >From: Trid <triddlywinks@...>
                >Reply-To: Distillers@yahoogroups.com
                >To: Distillers@yahoogroups.com
                >Subject: Re: [Distillers] Re: condensor
                >Date: Thu, 5 Apr 2007 06:54:36 -0700 (PDT)
                >
                >--- Harry <gnikomson2000@...> wrote:
                > > 5. Turbulence. Either or both of the fluids being turbulent is more
                > > efficient. Commonly it is accomplished by making sure there is
                > > something in the pathway of the vapour to force it to divert into
                > > the walls of the coolant carrier. It's automatic with coils as they
                > > are at rightangles to the vapour flowpath, and providing you put
                > > something in the centre space (like mesh) there's full turbulence.
                >
                ----snip----.
                > >
                > > If you consider all of the above you will see why Liebig-style
                > > condensers need to be so big or long. No turbulence is the culprit.

                That's what I hope I'm addressing in my "modified Liebig" design. The last
                1/4 or so of the 1/2" copper pipe vapor path is cross-drilled with 1/4"
                holes, spaced along the axis of the Liebig center on about 3/4" centers, and
                each rotated 90 degrees from the previous (and next) bore. Each of these
                bores has a segment of 1/4" copper tubing swaged and soldered into place,
                such that the last part of the vapor path is multiply interrupted by
                water-cooled copper, in a patter to induce turbulence.

                The reason for this design was experience with a wood-fired still I had many
                years ago, dealing with the wide range of energy utputs of a wood fire. In
                an earlier incarnation, the vapor path was reduced from 1/2" (nominal)
                diameter to 1/4" OD copper tubing as it entered the cooling jacket, and this
                condenser arrangement could be overwhelmed by large energy excursions of the
                wood fire, whereupon it would blow out the relief valve. When I extended
                about 10" of the 1/2" copper pipe inside the cooling jacket, my overpressure
                days were over, and I still got all the vapor cooling I could ever want.

                That's why my Liebig has perhaps 11" of unobstructed 1/2" copper vapor path
                to start, and a lot of turbulence and cooling surface at the end.

                >
                >They also have a poor surface area to length ratio. For example, a Liebig
                >with
                >a 1/2" inner pipe and a 24" water jacket has 37.7 sq.in. heat transfer
                >surface.
                > I have a counter-flow shotgun with 14 tubes with 1/4" id (think big, fat
                >Liebig with multiple tubes on the inside) and at only 12" long, has a
                >surface
                >area of 132 sq.in.
                >The up-side: Liebigs are very easy to clean.

                MY downside: Should I ever need to clean it, it would not be a pull-through.
                >
                >Trid
                >-really digging the idea of the cold-finger...condenser, you sick little
                >monkeys!!!

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              • Trid
                ... Sounds like a nice, long, stiff-bristled brush at about 3000rpm might be in order :) Which brings me back to a previously visited topic of cleaning. I
                Message 7 of 16 , Apr 5, 2007
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                  --- Robert Hubble <zymurgybob@...> wrote:

                  > >The up-side: Liebigs are very easy to clean.
                  >
                  > MY downside: Should I ever need to clean it, it would not be a pull-through.

                  Sounds like a nice, long, stiff-bristled brush at about 3000rpm might be in
                  order :)

                  Which brings me back to a previously visited topic of cleaning. I mostly
                  poststill and of course, that entails lots of "flavorful" residue on the vapor
                  side of my condenser tubes...especially when doing a batch of Absinthe. I
                  can't even imagine trying to get all that stuff out of a worm if one were to do
                  a batch of something else, say rum or whisky, lest it contaminate the flavor at
                  the very least.
                  I use a modular setup where my components are either slide-together (sealed
                  with silicone tape or plastic wrap if even necessary) or assembled with unions.
                  My cleanliness/flavor-contamination paranoia drove me to make everything
                  detachable, and with no more than a single 90 degree bend. So, as you would
                  deduce, I have a bucket full of elbows (both 45 and 90) all with unions on each
                  end. Then, if I need more cooling than one condenser can handle, I just put
                  another one on...if space is limited, I can put a couple elbows between them
                  and make a 180 degree bend and tweak the angles to fit. Since I graduated to
                  the shotgun condenser, I haven't encountered a need for additional cooling
                  capacity, so my modular rig has condensed (no pun intended) to where I only
                  need to direct the distillate spout towards the collection vessel. It's all
                  disassembleable so I can get a soapy brush to just about every surface that
                  will contact the vapors and get as much remaining residue off from the previous
                  batch as possible.

                  Concerning a number of prior posts questioning their cloudy spirit, often the
                  suggested culprit is tails left over from the previous batch. If this is the
                  case, then wouldn't this dictate discombobulating the head/condenser between
                  each and every spirit run such that tails don't contaminate the subsequent
                  batches? However, it doesn't quite add up...would this also necessitate
                  commercial pot still setups to thoroughly clean their stills between all runs?
                  I just can't imagine that allowing any kind of efficient business. Are tails
                  really such a contamination potential? Do sufficient heads rinse the tails
                  gunk out maybe? Perhaps it's too much of the tails-y heads in the middle?

                  ...or am I just being neurotic? :)

                  Trid
                  -neurotically yours
                • Harry
                  ... ... spirit, often the ... this is the ... head/condenser between ... subsequent ... necessitate ... between all runs? ... business. Are tails ...
                  Message 8 of 16 , Apr 5, 2007
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                    --- In Distillers@yahoogroups.com, Trid <triddlywinks@...> wrote:
                    <snip>
                    >
                    > Concerning a number of prior posts questioning their cloudy
                    spirit, often the
                    > suggested culprit is tails left over from the previous batch. If
                    this is the
                    > case, then wouldn't this dictate discombobulating the
                    head/condenser between
                    > each and every spirit run such that tails don't contaminate the
                    subsequent
                    > batches? However, it doesn't quite add up...would this also
                    necessitate
                    > commercial pot still setups to thoroughly clean their stills
                    between all runs?
                    > I just can't imagine that allowing any kind of efficient
                    business. Are tails
                    > really such a contamination potential? Do sufficient heads rinse
                    the tails
                    > gunk out maybe? Perhaps it's too much of the tails-y heads in the
                    middle?
                    >
                    > ...or am I just being neurotic? :)
                    >
                    > Trid
                    > -neurotically yours
                    >




                    You're gonna give your brain a hernia, Trid. :)

                    The simplest method of keeping condensers clean between runs
                    is...household white VINEGAR. It's not strong enough to eat away
                    your copper, but it does keep it REAL shiny.

                    At one time or another I've used Liebigs, coils and crossflows.
                    Assuming you have made them so they can be detached, do this...

                    Liebigs: Plug the outlet end with a cork. Fill the tube with
                    vinegar. Plug the other end with another cork. Store it until
                    required.

                    Coils and Crossflows: Drop them in a bucket of vinegar, enough to
                    cover the condenser completely. Put a lid on the bucket. Store
                    until required.

                    It only takes overnight to remove any residues in the condensers.

                    In all cases, RINSE WITH FRESH WATER BEFORE USE, as the vinegar will
                    turn blue (Sweitzers reagent, not really dangerous but I wouldn't
                    drink it).

                    Cleaning is that simple.


                    Slainte!
                    regards Harry
                  • Harry
                    Forgot to mention...the blue vinegar cleaning solution is reusable. Throw it out when it starts getting too much gunk in it. I typically reuse it for about a
                    Message 9 of 16 , Apr 5, 2007
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                      Forgot to mention...the blue vinegar cleaning solution is reusable.
                      Throw it out when it starts getting too much gunk in it. I typically
                      reuse it for about a year.

                      Slainte!
                      regards Harry
                    • Trid
                      ... What s the typical concentration that you use? Trid -humblest apologies for the brain hurty :)
                      Message 10 of 16 , Apr 5, 2007
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                        --- Harry <gnikomson2000@...> wrote:

                        > Forgot to mention...the blue vinegar cleaning solution is reusable.
                        > Throw it out when it starts getting too much gunk in it. I typically
                        > reuse it for about a year.
                        >
                        > Slainte!
                        > regards Harry

                        What's the typical concentration that you use?

                        Trid
                        -humblest apologies for the brain hurty :)
                      • Harry
                        ... Standard white table vinegar, it s 5% acetic acid. Use it neat. In Oz we buy cheap homebrand stuff from the supermarkets for about 50 cents per litre. I
                        Message 11 of 16 , Apr 6, 2007
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                          --- In Distillers@yahoogroups.com, Trid <triddlywinks@...> wrote:
                          >
                          > What's the typical concentration that you use?
                          >
                          > Trid
                          > -humblest apologies for the brain hurty :)
                          >



                          Standard white table vinegar, it's 5% acetic acid. Use it neat. In
                          Oz we buy cheap homebrand stuff from the supermarkets for about 50
                          cents per litre. I get 5 x 4lt plastic containers of it about once a
                          year.

                          Slainte!
                          regards Harry
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