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Re: Why does nobody paint the cooling spiral?

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  • abbababbaccc
    Hmm, I know black does indeed increase absorption of different vawelengths of light. How does it increase the molecular level heat transfer in between metal
    Message 1 of 21 , Apr 29, 2006
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      Hmm, I know black does indeed increase absorption of different
      vawelengths of light. How does it increase the molecular level heat
      transfer in between metal and air?

      - Riku

      --- In new_distillers@yahoogroups.com, "Jan Wouter"
      <janwouter.mailgroups@...> wrote:
      >
      > Funny, I was thinking about this also. I also was thinking about
      adding
      > cooling fins to add to the column. Painting it black would increase
      the
      > radiation and also efficiency.
      >
      > Regards
      > Jan Wouter
      >
      > 2006/4/28, grafoszillo <erikhermann@...>:
      > >
      > > It should be a well known fact, that blank metal does not radiate
      heat
      > > very well. A painted metal surface (preferably black) radiates
      much
      > > better.
      > > That's the reason why e.g. central heating radiators and
      electrical
      > > busbars are always painted.
      > >
      > > But everyone leaves the copper tube of the cooling spiral blank,
      or
      > > even polishes it.
      > >
      > > While most heat transfer happens by convection, a painted spiral
      > > should add a good amount of raddiation.
      > > Did somone ever try this?
      > >
      > > Cheers
      > > grafoszillo
      > >
      > >
      >
      >
      > [Non-text portions of this message have been removed]
      >
    • Paul McMillan
      No, painting it black would act as an insulator and make it less efficient.
      Message 2 of 21 , Apr 29, 2006
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        No, painting it black would act as an insulator and make it less efficient.

        On 4/29/06, Jan Wouter <janwouter.mailgroups@...> wrote:
        > Funny, I was thinking about this also. I also was thinking about adding
        > cooling fins to add to the column. Painting it black would increase the
        > radiation and also efficiency.
        >
        > Regards
        > Jan Wouter
        >
        > 2006/4/28, grafoszillo <erikhermann@...>:
        > >
        > > It should be a well known fact, that blank metal does not radiate heat
        > > very well. A painted metal surface (preferably black) radiates much
        > > better.
        > > That's the reason why e.g. central heating radiators and electrical
        > > busbars are always painted.
        > >
        > > But everyone leaves the copper tube of the cooling spiral blank, or
        > > even polishes it.
        > >
        > > While most heat transfer happens by convection, a painted spiral
        > > should add a good amount of raddiation.
        > > Did somone ever try this?
        > >
        > > Cheers
        > > grafoszillo
        > >
        > >
        >
        >
        > [Non-text portions of this message have been removed]
        >
        >
        >
        >
        >
        > New Distillers group archives are at http://archive.nnytech.net/
        > FAQ and other information available at http://homedistiller.org
        >
        >
        > Yahoo! Groups Links
        >
        >
        >
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        >
        >
        >
      • Trid
        ... heat ... Quite the contrary. It is a well known fact that blank metal transmit thermal energy better than metal with anything on its surface. The thicker
        Message 3 of 21 , Apr 29, 2006
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          --- In new_distillers@yahoogroups.com, "grafoszillo"
          <erikhermann@...> wrote:
          >
          > It should be a well known fact, that blank metal does not radiate
          heat
          > very well.

          Quite the contrary. It is a well known fact that blank metal
          transmit thermal energy better than metal with anything on its
          surface. The thicker the material, the slower energy is transmitted
          from inside to outside.

          > A painted metal surface (preferably black) radiates much
          > better.

          Again, no. ANYTHING that adds thickness to a material will reduce
          its ability to transmit (radiate if you will) thermal energy. On
          top of that, paint of any sort has a lower ability to transmit
          thermal energy than metal. Therefore, the effective reduction of
          heat transfer is even greater than if one had added an equivalent
          thickness of the same metal. [1]

          Now metal painted flat black would absorb radiant heat energy (e.g.
          sunlight) more readily than shiny metal as it essentially "fails to
          reflect" that light and the energy is resultantly absorbed.

          > That's the reason why e.g. central heating radiators and electrical
          > busbars are always painted.

          Still no. Most radiators are painted for aesthetic purposes because
          they're in plain sight. If you ever look at the heat transfer
          surfaces in central AC (both heating and cooling) systems, you'll
          find bare metal. Electrical busbars are painted for either phase
          identification or electrical insulation.

          > But everyone leaves the copper tube of the cooling spiral blank, or
          > even polishes it.

          As mentioned by another, shiny copper is pretty.

          > While most heat transfer happens by convection, a painted spiral
          > should add a good amount of raddiation.

          Ultimately, any paint will suffice more as insulation (if even
          slight) than added heat transfer ability. For our purposes, the
          thinner the wall of the heat transfer surface, the more efficient it
          will be. The more thermally conductive that wall is (copper vs.
          plastic as an example), the more efficient it will be. Obviously
          there may be metals that are more thermally conductive than copper,
          however, toxicity and expense are some of the factors that eliminate
          most.

          Trid
          -thermodynamics is my friend, no, make that *our* friend :)

          [1]
          There may well be an exception to this statement in the case of a
          metallic based paint. Though I would suspect it is something that's
          highly specialized and prohibitively expensive. However, this still
          doesn't change the fact that added paint (no matter HOW thermally
          conductive) adds to thickness and therfore to reduced heat transfer
          capability.
        • aborzachtd
          The term for the ability to radiate heat energy is emissivity. Perfect emissivity is 1. It is my understanding that ambient still air heatsinks for large
          Message 4 of 21 , Apr 29, 2006
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            The term for the ability to radiate heat energy is emissivity. Perfect
            emissivity is 1.

            It is my understanding that ambient still air heatsinks for large
            transistor amplifiers use conduction (convection) with air to get rid
            of about 75% of the heat they remove and 25% is removed through
            emission (emissivity). Naturally, their surfaces are anodized black.

            Here is a listing of typical emissivity ratings:
            http://www.technifab.com/heat-trans-inter2.htm

            If you look down the list you will see that polished copper has an
            emissivity of .023 but if has a thick oxide layer it is .78. That is
            an increase of almost 40 times in favor of the thick oxide layer!

            The lesson is clear. If you want to keep heat in (reflux column,
            boiler etc.), polish it. If you what to let heat out (coil, etc.) let
            it tarnish.

            Paint or chemical stain can improve the situation if applied very,
            very thinly. Otherwise they can act as an insulator. Black anodizing
            is used on aluminum because it offers virtually no insulation at all.
            If you can find a way to chemicaly stain copper black, its emissivity
            should go above .78.

            The emissivity rules also apply to water cooled condensers. The
            emissivity stays the same, but because water is so much better at
            cooling than air, the % of heat loss due to emission (emissivity) in
            such a case is lower than the 25% mentioned above.

            And to answer your question below, it doesn't. If you want to do that,
            make the surface rough to prevent laminar flow and add air flow.
            Indeed, if you can do the same to the inside surface of tubes you will
            improve efficiency as well. You need turbulence, not laminar flow to
            improve heat transferance.

            ab

            --- In new_distillers@yahoogroups.com, "abbababbaccc"
            <abbababbaccc@...> wrote:
            >
            > Hmm, I know black does indeed increase absorption of different
            > vawelengths of light. How does it increase the molecular level heat
            > transfer in between metal and air?
            >
            > - Riku
          • Harry
            ... Guys, can we transfer this discussion over to the Distillers Group? You re frightening the newbies. Slainte! regards Harry
            Message 5 of 21 , Apr 29, 2006
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              --- In new_distillers@yahoogroups.com, "aborzachtd" <aborza@...> wrote:
              >
              > --- In new_distillers@yahoogroups.com, "abbababbaccc"
              > <abbababbaccc@> wrote:



              Guys, can we transfer this discussion over to the Distillers Group?
              You're frightening the newbies.


              Slainte!
              regards Harry
            • sonum norbu
              Frightening????? NAHHHHHHHH The question has been answered seven million times already. It s an interesting thread watching all the pros and cons but
              Message 6 of 21 , Apr 29, 2006
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                Frightening????? NAHHHHHHHH The question has been answered seven
                million times already. It's an interesting thread watching all the
                'pros' and cons but that's all...blanikdog :))



                ----- Original Message -----
                From: Harry
                To: new_distillers@yahoogroups.com
                Subject: [new_distillers] Transfer it: (was) Re: Why does nobody
                paint the cooling spiral?
                Date: Sun, 30 Apr 2006 00:53:11 -0000

                --- In new_distillers@yahoogroups.com, "aborzachtd" <aborza@...>
                wrote:
                >
                > --- In new_distillers@yahoogroups.com, "abbababbaccc"
                > <abbababbaccc@> wrote:



                Guys, can we transfer this discussion over to the Distillers Group?
                You're frightening the newbies.


                Slainte!
                regards Harry





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                [Non-text portions of this message have been removed]
              • abbababbaccc
                Thanks ab, that was new to me. So basically it seems to be beneficial to let your reflux coil (+ other condensers) and column packing get oxidized. - Riku ...
                Message 7 of 21 , Apr 29, 2006
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                  Thanks ab, that was new to me. So basically it seems to be beneficial
                  to let your reflux coil (+ other condensers) and column packing get
                  oxidized.

                  - Riku

                  --- In new_distillers@yahoogroups.com, "aborzachtd" <aborza@...>
                  wrote:
                  >
                  > The term for the ability to radiate heat energy is emissivity.
                  Perfect
                  > emissivity is 1.
                  >
                  > It is my understanding that ambient still air heatsinks for large
                  > transistor amplifiers use conduction (convection) with air to get
                  rid
                  > of about 75% of the heat they remove and 25% is removed through
                  > emission (emissivity). Naturally, their surfaces are anodized black.
                  >
                  > Here is a listing of typical emissivity ratings:
                  > http://www.technifab.com/heat-trans-inter2.htm
                  >
                  > If you look down the list you will see that polished copper has an
                  > emissivity of .023 but if has a thick oxide layer it is .78. That
                  is
                  > an increase of almost 40 times in favor of the thick oxide layer!
                  >
                  > The lesson is clear. If you want to keep heat in (reflux column,
                  > boiler etc.), polish it. If you what to let heat out (coil, etc.)
                  let
                  > it tarnish.
                  >
                  > Paint or chemical stain can improve the situation if applied very,
                  > very thinly. Otherwise they can act as an insulator. Black
                  anodizing
                  > is used on aluminum because it offers virtually no insulation at
                  all.
                  > If you can find a way to chemicaly stain copper black, its
                  emissivity
                  > should go above .78.
                  >
                  > The emissivity rules also apply to water cooled condensers. The
                  > emissivity stays the same, but because water is so much better at
                  > cooling than air, the % of heat loss due to emission (emissivity)
                  in
                  > such a case is lower than the 25% mentioned above.
                  >
                  > And to answer your question below, it doesn't. If you want to do
                  that,
                  > make the surface rough to prevent laminar flow and add air flow.
                  > Indeed, if you can do the same to the inside surface of tubes you
                  will
                  > improve efficiency as well. You need turbulence, not laminar flow
                  to
                  > improve heat transferance.
                  >
                  > ab
                  >
                  > --- In new_distillers@yahoogroups.com, "abbababbaccc"
                  > <abbababbaccc@> wrote:
                  > >
                  > > Hmm, I know black does indeed increase absorption of different
                  > > vawelengths of light. How does it increase the molecular level
                  heat
                  > > transfer in between metal and air?
                  > >
                  > > - Riku
                  >
                • richardt2005
                  ... We re talking about 2 completely different cooling mechanisms. Radiation and conduction. Everything radiates because it s warm. At above 700 degrees or
                  Message 8 of 21 , Apr 29, 2006
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                    --- In new_distillers@yahoogroups.com, "abbababbaccc"
                    <abbababbaccc@...> wrote:
                    >
                    > Hmm, I know black does indeed increase absorption of different
                    > vawelengths of light. How does it increase the molecular level heat
                    > transfer in between metal and air?

                    We're talking about 2 completely different cooling mechanisms.
                    Radiation and conduction. Everything radiates because it's warm. At
                    above 700 degrees or so, what's being radiated is in the visible
                    range. At 100 degrees it's infrared, about 3-5 micron wavelength.
                    Painting something black does increase the amount that it's radiating.

                    But most of the cooling in these coils is conduction. It heats up the
                    air that's touching it, that air rises, it's displaced by cool air,
                    repeat. Adding fins, wrapping in pot scrubbers, blowing a fan at it
                    will all increase cooling.

                    I don't know if an increas in cooling will get you anything.
                  • Harry
                    ... beneficial ... get ... NOT the packing, Riku. There s more reasons for using copper than just heat transfer. While ab may have a point about improving
                    Message 9 of 21 , Apr 30, 2006
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                      --- In new_distillers@yahoogroups.com, "abbababbaccc"
                      <abbababbaccc@...> wrote:
                      >
                      > Thanks ab, that was new to me. So basically it seems to be
                      beneficial
                      > to let your reflux coil (+ other condensers) and column packing
                      get
                      > oxidized.
                      >
                      > - Riku



                      NOT the packing, Riku. There's more reasons for using copper than
                      just heat transfer. While ab may have a point about improving the
                      transfer in air-cooled coils (they'd need all the help they can get,
                      as your own experiments prove), the purpose of using shiny clean
                      mesh in the vapour path is not just for separation purposes. Copper
                      in the path reacts with any sulfides in the vapours, forming those
                      oxide deposits and other gunk that you see in the packing after a
                      run. If you already have that mesh oxidised, the pure copper cannot
                      work its magic. End result, stinky nasty booze.

                      But for the sake of experimentation, by all means try it for a few
                      runs. Report back any findings. Who knows, it could be a winner.
                      If not, you can always bicarb and redistill (lots of invested time &
                      energy, but a decisive learning experience). But that's what this
                      hobby is all about.


                      Slainte!
                      regards Harry
                    • abbababbaccc
                      Actually I ve run with very oxidiced amphora mesh and I didn t notice any ill effects. Though I must admitt I didn t notice much benefit either - so I guess
                      Message 10 of 21 , Apr 30, 2006
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                        Actually I've run with very oxidiced amphora mesh and I didn't notice
                        any ill effects. Though I must admitt I didn't notice much benefit
                        either - so I guess it's all within the usual operating error margin.

                        - Riku

                        --- In new_distillers@yahoogroups.com, "Harry" <gnikomson2000@...>
                        wrote:
                        >
                        > --- In new_distillers@yahoogroups.com, "abbababbaccc"
                        > <abbababbaccc@> wrote:
                        > >
                        > > Thanks ab, that was new to me. So basically it seems to be
                        > beneficial
                        > > to let your reflux coil (+ other condensers) and column packing
                        > get
                        > > oxidized.
                        > >
                        > > - Riku
                        >
                        >
                        >
                        > NOT the packing, Riku. There's more reasons for using copper than
                        > just heat transfer. While ab may have a point about improving the
                        > transfer in air-cooled coils (they'd need all the help they can
                        get,
                        > as your own experiments prove), the purpose of using shiny clean
                        > mesh in the vapour path is not just for separation purposes.
                        Copper
                        > in the path reacts with any sulfides in the vapours, forming those
                        > oxide deposits and other gunk that you see in the packing after a
                        > run. If you already have that mesh oxidised, the pure copper
                        cannot
                        > work its magic. End result, stinky nasty booze.
                        >
                        > But for the sake of experimentation, by all means try it for a few
                        > runs. Report back any findings. Who knows, it could be a winner.
                        > If not, you can always bicarb and redistill (lots of invested time
                        &
                        > energy, but a decisive learning experience). But that's what this
                        > hobby is all about.
                        >
                        >
                        > Slainte!
                        > regards Harry
                        >
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