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39077Re: [Distillers] Re: condensor

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  • Trid
    Apr 5, 2007
      --- 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.

      -really digging the idea of the cold-finger...condenser, you sick little monkeys!!!
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