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Re: [Distillers] Re: Reflux Valve = Temperature Controller (?)

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  • Mike Nixon
    peter_vcb wrote: Subject: [Distillers] Re: Reflux Valve = Temperature Controller (?) MIKE N- could you please comment on Johans 1/2 copper tube still. 95%
    Message 1 of 17 , Mar 31, 2003
      peter_vcb wrote:
      Subject: [Distillers] Re: Reflux Valve = Temperature Controller (?)

      MIKE N- could you please comment on Johans 1/2" copper tube still.
      95% from a 3% wash with no packing, what is going on there! all i can consider is that the tube is so narrow that the vapour is exposed to a large surface area just like packing.
      =============================
      Hi Peter,
       
      I'll give it a go, but first thanks to Johan for the pic.  Helps a lot, so I've shoved it in here as well
      Rodmac is right ... with those indentations it's reminiscent of a Vigreux condenser that has its internal surface area increased by lots of indentations.
      As I see it, the main feature of Johan's procedure is that it is deliberately kept very slow, so the vapor is moving up this column at a very low speed indeed.  As in a lyne arm, vapor will condense on the walls and some of this liquid will be re-evaporated to give vapor with a higher concentration of volatiles.  Stripped liquid will accumulate and trickle back down, and the richer vapor will condense a little further up to repeat the process.  As the vapor speed is very low, we can think of the column in Tony's terms as having a very small HETP, so we can envisage this liquid/vapor interchange being repeated many, many times before the vapor reaches the top, resulting in good separation.
       
      The low speed of the vapor is one important factor.  The other is the surface/volume ratio.  Same reasoning that we use with packing ... the greater the surface area of the liquid in a given volume of vapor, then the more efficient the evaporation interchange will be.  Now the ratio between the internal surface area of a tube and its volume (which will be the same thing as liquid surface area/vapor volume) is very simple: it's 4/D, where D is the diameter.  Other things like length and Pi all cancel out.  Johan is using 1/2" diameter tubing, so the ratio is 8.  Compare this with, say, a 2" diameter tube where the ratio is just 2.  He has also increased this ratio slightly by getting busy with his trusty Thor's Hammer, so the ratio could possibly be nearer 9 than 8.  We can also see that if he had used 1/4" diameter tubing them the ratio would be up to 16.
       
      I reckon that it is this combination of slow vapor speed and fairly high surface/volume ratio that makes Johan's method work so well.  I would also think that using several 1/4" diameter tubes would be even better ... the surface/volume ratio would remain the same of course (16), but the volume being processed would increase with every extra tube used.  However, if anyone cares to see is this works, I wouldn't bother with the indentations.  They are a good idea with 1/2" tubing, but the slight increase in surface area you would get with 1/4" diameter wouldn't be worth mangling a bunch of nice copper tubing that could be used for other purposes at another time.
       
      Make any sense?
       
      Mike N
       


    • Johan
      ... Från: Mike Nixon [mailto:mike@silverkey.co.nz] Skickat: den 31 mars 2003 23:20 Till: Distillers@yahoogroups.com Ämne: Re: [Distillers] Re: Reflux Valve =
      Message 2 of 17 , Mar 31, 2003

         

         

        -----Ursprungligt meddelande-----
        Från: Mike Nixon [mailto:mike@...]
        Skickat: den 31 mars 2003 23:20
        Till: Distillers@yahoogroups.com
        Ämne: Re: [Distillers] Re: Reflux Valve = Temperature Controller (?)

         

        peter_vcb wrote:
        Subject: [Distillers] Re: Reflux Valve = Temperature Controller (?)

        MIKE N- could you please comment on Johans 1/2" copper tube still.
        95% from a 3% wash with no packing, what is going on there! all i can consider is that the tube is so narrow that the vapour is exposed to a large surface area just like packing.

        =============================

        Hi Peter,

         

        I'll give it a go, but first thanks to Johan for the pic.  Helps a lot, so I've shoved it in here as well

        Rodmac is right ... with those indentations it's reminiscent of a Vigreux condenser that has its internal surface area increased by lots of indentations.

         

        As I see it, the main feature of Johan's procedure is that it is deliberately kept very slow, so the vapor is moving up this column at a very low speed indeed. 

        --

        >

        I should give it a try with much less heat, I have only tried it with 500-550W because of the thermostat regulated boiler, so vapour speed is high.

        But the reflux was high as well when I got 95%

        On the other hand reflux was low when I got 92% from about 12 % mash and 550W

         

        I wonder how it will work with less heat..

        --

         

         As in a lyne arm, vapor will condense on the walls and some of this liquid will be re-evaporated to give vapor with a higher concentration of volatiles.  Stripped liquid will accumulate and trickle back down, and the richer vapor will condense a little further up to repeat the process.  As the vapor speed is very low, we can think of the column in Tony's terms as having a very small HETP, so we can envisage this liquid/vapor interchange being repeated many, many times before the vapor reaches the top, resulting in good separation.

         

        The low speed of the vapor is one important factor.  The other is the surface/volume ratio.  Same reasoning that we use with packing ... the greater the surface area of the liquid in a given volume of vapor, then the more efficient the evaporation interchange will be.  Now the ratio between the internal surface area of a tube and its volume (which will be the same thing as liquid surface area/vapor volume) is very simple: it's 4/D, where D is the diameter.  Other things like length and Pi all cancel out.  Johan is using 1/2" diameter tubing, so the ratio is 8.  Compare this with, say, a 2" diameter tube where the ratio is just 2.  He has also increased this ratio slightly by getting busy with his trusty Thor's Hammer, so the ratio could possibly be nearer 9 than 8.  We can also see that if he had used 1/4" diameter tubing them the ratio would be up to 16.

         

        I reckon that it is this combination of slow vapor speed and fairly high surface/volume ratio that makes Johan's method work so well.  I would also think that using several 1/4" diameter tubes would be even better ... the surface/volume ratio would remain the same of course (16), but the volume being processed would increase with every extra tube used.  However, if anyone cares to see is this works, I wouldn't bother with the indentations.  They are a good idea with 1/2" tubing, but the slight increase in surface area you would get with 1/4" diameter wouldn't be worth mangling a bunch of nice copper tubing that could be used for other purposes at another time.

         

        Make any sense?

         

        Mike N

         

         



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      • Mike Nixon
        Johan wrote: Subject: SV: [Distillers] Re: Reflux Valve = Temperature Controller (?) I should give it a try with much less heat, I have only tried it with
        Message 3 of 17 , Mar 31, 2003
          Johan wrote:
          Subject: SV: [Distillers] Re: Reflux Valve = Temperature Controller (?)

          I should give it a try with much less heat, I have only tried it with 500-550W because of the thermostat regulated boiler, so vapour speed is high.
          But the reflux was high as well when I got 95%
          On the other hand reflux was low when I got 92% from about 12 % mash and 550W

          I wonder how it will work with less heat..
          ===========================================
          Much better separation I reckon.  I had no idea you were running it at that power ... I had imagined that it was much lower.
          At 550W, speed of vapor in a 1/2" diameter column is 109 cm/sec!  That is seriously FAST
           
          Mike N
           
        • peter_vcb
          hi Mike makes lots of sense, thanks. i did an excel file after i posted yesterday to see the variance in the ratio just like you mention. i got different
          Message 4 of 17 , Apr 1, 2003
            hi Mike
            makes lots of sense, thanks. i did an excel file after i posted
            yesterday to see the variance in the ratio just like you mention. i
            got different ratios than you (i used mm) but same ratios between
            diameters (i.e. 1/2" was 4 times 2"). i tried putting them into Tonys
            calculators but gave up quickly! Johan initialy had an undeformed
            tube and still got high strength. i am planning on making one with
            several columns. i found out 1/2" 316 s/s tube is cheaper than copper
            for me so i will use that (just over 2euro per metre). i figure that
            i can add many columns and if they are tall enough and identical i
            should get an even output from each of them (and hence run at high
            power). i am thinking of columns 4 or 5 metres high without
            insulation for the top metre to cause some ambient reflux. i think if
            they are outdoors then the long fall of 4 metres on the output side
            may mean they need no cooling at all. i will make one and get it
            right before replicating the other columns.

            Peter

            --- In Distillers@yahoogroups.com, "Mike Nixon" <mike@s...> wrote:
            > peter_vcb wrote:
            > Subject: [Distillers] Re: Reflux Valve = Temperature Controller (?)
            >
            > MIKE N- could you please comment on Johans 1/2" copper tube still.
            > 95% from a 3% wash with no packing, what is going on there! all i
            can consider is that the tube is so narrow that the vapour is exposed
            to a large surface area just like packing.
            > =============================
            > Hi Peter,
            >
            > I'll give it a go, but first thanks to Johan for the pic. Helps a
            lot, so I've shoved it in here as well
            > Rodmac is right ... with those indentations it's reminiscent of a
            Vigreux condenser that has its internal surface area increased by
            lots of indentations.
            >
            > As I see it, the main feature of Johan's procedure is that it is
            deliberately kept very slow, so the vapor is moving up this column at
            a very low speed indeed. As in a lyne arm, vapor will condense on
            the walls and some of this liquid will be re-evaporated to give vapor
            with a higher concentration of volatiles. Stripped liquid will
            accumulate and trickle back down, and the richer vapor will condense
            a little further up to repeat the process. As the vapor speed is
            very low, we can think of the column in Tony's terms as having a very
            small HETP, so we can envisage this liquid/vapor interchange being
            repeated many, many times before the vapor reaches the top, resulting
            in good separation.
            >
            > The low speed of the vapor is one important factor. The other is
            the surface/volume ratio. Same reasoning that we use with
            packing ... the greater the surface area of the liquid in a given
            volume of vapor, then the more efficient the evaporation interchange
            will be. Now the ratio between the internal surface area of a tube
            and its volume (which will be the same thing as liquid surface
            area/vapor volume) is very simple: it's 4/D, where D is the
            diameter. Other things like length and Pi all cancel out. Johan is
            using 1/2" diameter tubing, so the ratio is 8. Compare this with,
            say, a 2" diameter tube where the ratio is just 2. He has also
            increased this ratio slightly by getting busy with his trusty Thor's
            Hammer, so the ratio could possibly be nearer 9 than 8. We can also
            see that if he had used 1/4" diameter tubing them the ratio would be
            up to 16.
            >
            > I reckon that it is this combination of slow vapor speed and fairly
            high surface/volume ratio that makes Johan's method work so well. I
            would also think that using several 1/4" diameter tubes would be even
            better ... the surface/volume ratio would remain the same of course
            (16), but the volume being processed would increase with every extra
            tube used. However, if anyone cares to see is this works, I wouldn't
            bother with the indentations. They are a good idea with 1/2" tubing,
            but the slight increase in surface area you would get with 1/4"
            diameter wouldn't be worth mangling a bunch of nice copper tubing
            that could be used for other purposes at another time.
            >
            > Make any sense?
            >
            > Mike N
          • Mike Nixon
            peter_vcb wrote: Subject: [Distillers] Re: Reflux Valve = Temperature Controller (?) hi Mike makes lots of sense, thanks. i did an excel file after i posted
            Message 5 of 17 , Apr 1, 2003
              peter_vcb wrote:
              Subject: [Distillers] Re: Reflux Valve = Temperature Controller (?)

              hi Mike
              makes lots of sense, thanks. i did an excel file after i posted yesterday to see the variance in the ratio just like you mention. i
              got different ratios than you (i used mm)  .....
              ============================
              Hi Peter,
              The way I figured it, the circumference of a cylinder diameter D is (Pi)D, so the surface area is(Pi)DL
              The volume of that cylinder is (Pi)D2L/4
              so the ratio of surface area/volume came to 4(Pi)DL / (Pi)D2L  .... or 4/D
              Snag is, the dimensions of this are "per length" so yes, the number you get will indeed depend on what units you use, so it's better to get rid of that length by comparing different tubes to get a dimensionless number.
               
              So if we compare tube A with diameter Da with tube B with diameter Db we get TubeA/Tube B = Db/Da
              Suppose Tube A is 1/4 inches diameter and tube B is 2 inches diameter, we get Db/Da = 2*4 = 8
              In metric terms ... Tube A is 1/4 * 25.5 mm diameter and tube B is 2 * 25.4 mm diameter, and the ratio is again 8.
              In words, Tube A has 8 times as much surface area per volume than tube B
               
              Better?
              Mike N
            • homedistiller
              Hi all, I also follow, with interest, the pipe column experiments. On the next page, it says that a single, (insulated of course!) open tube column of 6 mm
              Message 6 of 17 , Apr 2, 2003
                Hi all,
                I also follow, with interest, the "pipe column" experiments.
                On the next page, it says that a single, (insulated of course!) open
                tube column of 6 mm (.25 inch) has a plate height of 80 cm for a
                throughput of 10 ml/minute.

                http://ull.chemistry.uakron.edu/chemsep/slide.html$Chapter=/chemsep/
                distillation/&Last=34&Slide=31

                I was thinking of just stretching a thin polypropylene rope, copper
                electricity wire, stainless steel cable (2 or 3 mm diameter ?) inside
                this column.
                The slightest obstruction inside this pipe would instantly reduce the
                plate height and thus create many more stages for the same length of
                pipe. It would increase the contact surface, would reduce the
                downward velocity of the reflux and a rope or a cable can be easily
                removed for cleaning purposes.

                As Mike Nixon proposed already in an earlier post, similar of those
                "pipe columns" can be bundled in parallel.

                Dirk




                --- In Distillers@yahoogroups.com, "Mike Nixon" <mike@s...> wrote:
                > peter_vcb wrote:
                > Subject: [Distillers] Re: Reflux Valve = Temperature Controller (?)
                >
                > hi Mike
                > makes lots of sense, thanks. i did an excel file after i posted
                yesterday to see the variance in the ratio just like you mention. i
                > got different ratios than you (i used mm) .....
                > ============================
                > Hi Peter,
                > The way I figured it, the circumference of a cylinder diameter D is
                (Pi)D, so the surface area is(Pi)DL
                > The volume of that cylinder is (Pi)D2L/4
                > so the ratio of surface area/volume came to 4(Pi)DL / (Pi)D2L ....
                or 4/D
                > Snag is, the dimensions of this are "per length" so yes, the number
                you get will indeed depend on what units you use, so it's better to
                get rid of that length by comparing different tubes to get a
                dimensionless number.
                >
                > So if we compare tube A with diameter Da with tube B with diameter
                Db we get TubeA/Tube B = Db/Da
                > Suppose Tube A is 1/4 inches diameter and tube B is 2 inches
                diameter, we get Db/Da = 2*4 = 8
                > In metric terms ... Tube A is 1/4 * 25.5 mm diameter and tube B is
                2 * 25.4 mm diameter, and the ratio is again 8.
                > In words, Tube A has 8 times as much surface area per volume than
                tube B
                >
                > Better?
                > Mike N
              • peter_vcb
                Mike, yep i was working the same way using mm and using a standard length of 1m. so do you think Johans coiled copper tube idea would work as well or even
                Message 7 of 17 , Apr 2, 2003
                  Mike,
                  yep i was working the same way using mm and using a standard length
                  of 1m.
                  so do you think Johans coiled copper tube idea would work as well or
                  even better? if coiled the cooled vapour will flow down the tube
                  whereas if it is vertical it may fall straight down and the tube may
                  experience less wetting of the available surface. conversely it will
                  only flow on the lower section of the tube so vertical may be better.
                  if a coiled one would work it would easier to use indoors you could
                  have 10metres coiled to a low height. it could coil up fully
                  insulated and coil back down over itself with a fan blowing on it. i
                  still have this idea of a nice efficient radiator in my room pumping
                  out booze all day and keeping me warm :-)

                  if it scaled up perfectly (i know it wont) a 2" column would need to
                  be 6m high to work the same as the 1/2" 1.5m column. the cross
                  section area of a 2" column is 16 times that of a 1/2" column. so to
                  run at the same power i would need 16 columns at 1.5m which is 24m of
                  1/2" tube (56euro to me) compared to 6m of 2" tube (105euro). so has
                  anybody heard of a very high column run with no scrubbers? cheaper
                  than copper of s/s would be scaffolding poles. you could get 6m very
                  cheap and redistill the output to leave the nasties behind.

                  Peter


                  --- In Distillers@yahoogroups.com, "Mike Nixon" <mike@s...> wrote:
                  > peter_vcb wrote:
                  > Subject: [Distillers] Re: Reflux Valve = Temperature Controller (?)
                  >
                  > hi Mike
                  > makes lots of sense, thanks. i did an excel file after i posted
                  yesterday to see the variance in the ratio just like you mention. i
                  > got different ratios than you (i used mm) .....
                  > ============================
                  > Hi Peter,
                  > The way I figured it, the circumference of a cylinder diameter D is
                  (Pi)D, so the surface area is(Pi)DL
                  > The volume of that cylinder is (Pi)D2L/4
                  > so the ratio of surface area/volume came to 4(Pi)DL / (Pi)D2L ....
                  or 4/D
                  > Snag is, the dimensions of this are "per length" so yes, the number
                  you get will indeed depend on what units you use, so it's better to
                  get rid of that length by comparing different tubes to get a
                  dimensionless number.
                  >
                  > So if we compare tube A with diameter Da with tube B with diameter
                  Db we get TubeA/Tube B = Db/Da
                  > Suppose Tube A is 1/4 inches diameter and tube B is 2 inches
                  diameter, we get Db/Da = 2*4 = 8
                  > In metric terms ... Tube A is 1/4 * 25.5 mm diameter and tube B is
                  2 * 25.4 mm diameter, and the ratio is again 8.
                  > In words, Tube A has 8 times as much surface area per volume than
                  tube B
                  >
                  > Better?
                  > Mike N
                • Aaron Pelly
                  Did you never get your low power input-air cooled-heater-still to work? I had forgotten about it actually. What progress _did_ you make? ... ...
                  Message 8 of 17 , Apr 2, 2003
                    Did you never get your low power input-air cooled-heater-still to work?

                    I had forgotten about it actually.

                    What progress _did_ you make?

                    > -----Original Message-----
                    > From: peter_vcb [mailto:viciousblackout@...]
                    > Sent: Wednesday, 2 April 2003 21:55
                    > To: Distillers@yahoogroups.com
                    > Subject: [Distillers] Re: Reflux Valve = Temperature Controller (?)

                    <snip>
                    > i
                    > still have this idea of a nice efficient radiator in my room pumping
                    > out booze all day and keeping me warm :-)
                    <snip>
                  • peter_vcb
                    Hi Aaron i never actually tried it (it is made though). i made the air stripping still instead but it stank my room out and that was at 60C. my fan didnt have
                    Message 9 of 17 , Apr 2, 2003
                      Hi Aaron
                      i never actually tried it (it is made though). i made the air
                      stripping still instead but it stank my room out and that was at 60C.
                      my fan didnt have much of a cooling effect on that so i presumed it
                      would have had very little effect if it was actually boiling.

                      for those who missed it my plan was to have my own reflux still run
                      at such low power that it would only need air cooling and i could
                      leave it on all day long. i ran my reflux still it at about 600W and
                      got about 600ml per hour. if i made an "air liebeg" it may work. a
                      large diameter pvc tube with the copper outlet tube in it and a fan
                      blowing up it. Johans 1.5m 1/2" copper tube is a better and cheaper
                      bet, very easy to make and gives the same output. if the copper
                      outlet (or downturn on Johans) is long enough then it will cool by
                      ambient air if the power is low enough. otherwise i would have the
                      tube going into a worm in a bucket of water which would be changed
                      daily. my other idea is an outdoor still like Johans 1/2" tube but
                      have it about 5m high so it will be completely cool by the time it
                      travels downturned 5m of tube. the downturn tube could also be filled
                      with carbon to slow the distillate down to allow more cooling.

                      Peter


                      --- In Distillers@yahoogroups.com, "Aaron Pelly" <apelly@m...> wrote:
                      > Did you never get your low power input-air cooled-heater-still to
                      work?
                      >
                      > I had forgotten about it actually.
                      >
                      > What progress _did_ you make?
                      >
                      > > -----Original Message-----
                      > > From: peter_vcb [mailto:viciousblackout@y...]
                      > > Sent: Wednesday, 2 April 2003 21:55
                      > > To: Distillers@yahoogroups.com
                      > > Subject: [Distillers] Re: Reflux Valve = Temperature Controller
                      (?)
                      >
                      > <snip>
                      > > i
                      > > still have this idea of a nice efficient radiator in my room
                      pumping
                      > > out booze all day and keeping me warm :-)
                      > <snip>
                    • mwmccaw
                      Peter, what you are describing begins to sound a lot like a gas chromatography column, which is often a very long coil of very fine tubing. The key problem I
                      Message 10 of 17 , Apr 2, 2003
                        Peter, what you are describing begins to sound a lot like a gas
                        chromatography column, which is often a very long coil of very fine
                        tubing.
                        The key problem I see with what you describe will be heat loss - the
                        smaller the column diameter, the faster the heat loss per unit
                        length, so there will be a maximum length you can run - as soon as
                        the column temperature falls below 78 deg C, you're hosed....
                        You're right that you would have more potential area for reflux, and
                        that it should proceed downward more slowly, but it will also only
                        coat a fraction of the tube diameter.
                        In short, worthy of an experiment!
                        Mike McCaw



                        --- In Distillers@yahoogroups.com, "peter_vcb"
                        <viciousblackout@y...> wrote:
                        > Mike,
                        > yep i was working the same way using mm and using a standard
                        length
                        > of 1m.
                        > so do you think Johans coiled copper tube idea would work as well
                        or
                        > even better? if coiled the cooled vapour will flow down the tube
                        > whereas if it is vertical it may fall straight down and the tube
                        may
                        > experience less wetting of the available surface. conversely it
                        will
                        > only flow on the lower section of the tube so vertical may be
                        better.
                        > if a coiled one would work it would easier to use indoors you
                        could
                        > have 10metres coiled to a low height. it could coil up fully
                        > insulated and coil back down over itself with a fan blowing on it.
                        i
                        > still have this idea of a nice efficient radiator in my room
                        pumping
                        > out booze all day and keeping me warm :-)
                        >
                        > if it scaled up perfectly (i know it wont) a 2" column would need
                        to
                        > be 6m high to work the same as the 1/2" 1.5m column. the cross
                        > section area of a 2" column is 16 times that of a 1/2" column. so
                        to
                        > run at the same power i would need 16 columns at 1.5m which is 24m
                        of
                        > 1/2" tube (56euro to me) compared to 6m of 2" tube (105euro). so
                        has
                        > anybody heard of a very high column run with no scrubbers? cheaper
                        > than copper of s/s would be scaffolding poles. you could get 6m
                        very
                        > cheap and redistill the output to leave the nasties behind.
                        >
                        > Peter
                        >
                        >
                        > --- In Distillers@yahoogroups.com, "Mike Nixon" <mike@s...> wrote:
                        > > peter_vcb wrote:
                        > > Subject: [Distillers] Re: Reflux Valve = Temperature Controller
                        (?)
                        > >
                        > > hi Mike
                        > > makes lots of sense, thanks. i did an excel file after i posted
                        > yesterday to see the variance in the ratio just like you mention.
                        i
                        > > got different ratios than you (i used mm) .....
                        > > ============================
                        > > Hi Peter,
                        > > The way I figured it, the circumference of a cylinder diameter D
                        is
                        > (Pi)D, so the surface area is(Pi)DL
                        > > The volume of that cylinder is (Pi)D2L/4
                        > > so the ratio of surface area/volume came to 4(Pi)DL / (Pi)
                        D2L ....
                        > or 4/D
                        > > Snag is, the dimensions of this are "per length" so yes, the
                        number
                        > you get will indeed depend on what units you use, so it's better
                        to
                        > get rid of that length by comparing different tubes to get a
                        > dimensionless number.
                        > >
                        > > So if we compare tube A with diameter Da with tube B with
                        diameter
                        > Db we get TubeA/Tube B = Db/Da
                        > > Suppose Tube A is 1/4 inches diameter and tube B is 2 inches
                        > diameter, we get Db/Da = 2*4 = 8
                        > > In metric terms ... Tube A is 1/4 * 25.5 mm diameter and tube B
                        is
                        > 2 * 25.4 mm diameter, and the ratio is again 8.
                        > > In words, Tube A has 8 times as much surface area per volume
                        than
                        > tube B
                        > >
                        > > Better?
                        > > Mike N
                      • Johan
                        I agree that heatloss probably is a problem, but insulate it may not be so hard since it is a coil. Johan Peter, what you are describing begins to sound a lot
                        Message 11 of 17 , Apr 2, 2003
                          I agree that heatloss probably is a problem, but insulate it may not be so
                          hard since it is a coil.

                          Johan

                          Peter, what you are describing begins to sound a lot like a gas
                          chromatography column, which is often a very long coil of very fine
                          tubing.
                          The key problem I see with what you describe will be heat loss - the
                          smaller the column diameter, the faster the heat loss per unit
                          length, so there will be a maximum length you can run - as soon as
                          the column temperature falls below 78 deg C, you're hosed....
                          You're right that you would have more potential area for reflux, and
                          that it should proceed downward more slowly, but it will also only
                          coat a fraction of the tube diameter.
                          In short, worthy of an experiment!
                          Mike McCaw



                          --- In Distillers@yahoogroups.com, "peter_vcb"
                          <viciousblackout@y...> wrote:
                          > Mike,
                          > yep i was working the same way using mm and using a standard
                          length
                          > of 1m.
                          > so do you think Johans coiled copper tube idea would work as well
                          or
                          > even better? if coiled the cooled vapour will flow down the tube
                          > whereas if it is vertical it may fall straight down and the tube
                          may
                          > experience less wetting of the available surface. conversely it
                          will
                          > only flow on the lower section of the tube so vertical may be
                          better.
                          > if a coiled one would work it would easier to use indoors you
                          could
                          > have 10metres coiled to a low height. it could coil up fully
                          > insulated and coil back down over itself with a fan blowing on it.
                          i
                          > still have this idea of a nice efficient radiator in my room
                          pumping
                          > out booze all day and keeping me warm :-)
                          >
                          > if it scaled up perfectly (i know it wont) a 2" column would need
                          to
                          > be 6m high to work the same as the 1/2" 1.5m column. the cross
                          > section area of a 2" column is 16 times that of a 1/2" column. so
                          to
                          > run at the same power i would need 16 columns at 1.5m which is 24m
                          of
                          > 1/2" tube (56euro to me) compared to 6m of 2" tube (105euro). so
                          has
                          > anybody heard of a very high column run with no scrubbers? cheaper
                          > than copper of s/s would be scaffolding poles. you could get 6m
                          very
                          > cheap and redistill the output to leave the nasties behind.
                          >
                          > Peter
                          >
                          >
                          > --- In Distillers@yahoogroups.com, "Mike Nixon" <mike@s...> wrote:
                          > > peter_vcb wrote:
                          > > Subject: [Distillers] Re: Reflux Valve = Temperature Controller
                          (?)
                          > >
                          > > hi Mike
                          > > makes lots of sense, thanks. i did an excel file after i posted
                          > yesterday to see the variance in the ratio just like you mention.
                          i
                          > > got different ratios than you (i used mm) .....
                          > > ============================
                          > > Hi Peter,
                          > > The way I figured it, the circumference of a cylinder diameter D
                          is
                          > (Pi)D, so the surface area is(Pi)DL
                          > > The volume of that cylinder is (Pi)D2L/4
                          > > so the ratio of surface area/volume came to 4(Pi)DL / (Pi)
                          D2L ....
                          > or 4/D
                          > > Snag is, the dimensions of this are "per length" so yes, the
                          number
                          > you get will indeed depend on what units you use, so it's better
                          to
                          > get rid of that length by comparing different tubes to get a
                          > dimensionless number.
                          > >
                          > > So if we compare tube A with diameter Da with tube B with
                          diameter
                          > Db we get TubeA/Tube B = Db/Da
                          > > Suppose Tube A is 1/4 inches diameter and tube B is 2 inches
                          > diameter, we get Db/Da = 2*4 = 8
                          > > In metric terms ... Tube A is 1/4 * 25.5 mm diameter and tube B
                          is
                          > 2 * 25.4 mm diameter, and the ratio is again 8.
                          > > In words, Tube A has 8 times as much surface area per volume
                          than
                          > tube B
                          > >
                          > > Better?
                          > > Mike N



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