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30103Re: SS wall heat conduction math

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  • abbababbaccc
    Jun 1, 2005
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      Andrew, a mash temperature will typically vary inbetween 90C (~17%) -
      99C (~1%) during operation. IMO you'll get missleading results by
      using 78C for mash temperature.

      - Riku

      --- In Distillers@yahoogroups.com, Andrew Forsberg <andrew@u...>
      wrote:
      > Hi all,
      >
      > The internet has provided me with far too many conflicting rates and
      > formulae for calculating whether an external water bath for a
      stainless
      > steel boiler will or will not provide sufficient heat.
      >
      > I'd very much appreciate it if an engineer on the list would give
      this a
      > once over:
      >
      > T1 = 105 degC (water + table salt jacket)
      > T2 = 78 degC (mash)
      > Heat transfer coefficient = no idea... Ignoring it for the moment.
      > K = approx 14 W(m2 . K) (I have seen more figures for SS than I
      care to
      > poke sticks at. This is the most conservative, and is for 270K, so
      > anything better would be super).
      > Q = Watts
      > A = Area = .64m2
      > D = thickness of the SS wall = approx 2 mms
      >
      > Q/A = (T1 - T2) / (D . 1/K)
      >
      > Q/A = (27) / (.002 / 14)
      > = 27 . 7000
      > = 189,000
      >
      > Q = 189,000 . 0.64
      > = 120.96 kW
      >
      > So, what I'd like to know is -- will a 2mm stainless steel wall for
      an
      > area of .64m2 allow heat to pass through at a rate of up 120kW for
      that
      > temperature differential? Even approximately? As long as it's higher
      > than 3 or 4kW I'm happy. Unfortunately some formulae I've found
      > suggested the figure would be closer to 800W...
      >
      > Cheers and thanks,
      > Andrew
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