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hx design

Eric Johnson
Eric Johnson Member Posts: 174
I have a 150K btu flat plate heat exchanger, and my original plan was to pump tank water through one side and boiler water through the other. However, I'm not at all confident that it would work going both ways (storing and recovering) and I would rather have a stratified tank than a mixed one, which is what a flat plate or shell & tube would produce. At least in my small tank.

Based on people's experience with in-tank coils, I'm fairly confident that this would work, but I don't have a good sense of how big to make it. I mean if you do the math, a 200-foot 1" copper coil is what would be required for this boiler. However, people who know what they're talking about say I can probably get by with less. And since I have the rigid pipe and soft copper is about $5.50 a foot, I'd like to go with what I've got.


  • Eric Johnson
    Eric Johnson Member Posts: 174
    hx design

    I've pretty much decided to build a header-type heat exchanger (two, actually) for my nonpressurized heat storage tank. In another thread, hot rod suggested using silver solder to make the connections between the 1" headers and 1/2-inch feeder lines. I don't know why silver solder is better, but if hot rod suggests it, I'm doing it.

    Anyone have any other suggestions on the right way to do this? Attached is a pic of the connection I'm talking about.

    The boiler (wood gasification) is rated at 205K btu/hr. I'd like to have enough capacity to put most of into the tank on occasion. I'm thinking about building a series of these with 5-foot one-inch copper headers and 3-foot 1/2-inch feeders. I guess it would be better to overbuild it, but I really don't have a good feel for how much capacity I need. Any suggestions on the spacing of the 1/2-inch lines on the header and the number of these 3x5 units top and bottom? I want a dedicated hx on the bottom for stashing heat and a separate one on the top for recovery.

    Not that it matters, but the tank is 1,000 gallons, with potential expansion in the future to 2,500 gal.
  • Ken_40
    Ken_40 Member Posts: 1,320

    this would be faster, cheaper, better engineered, known results based on engineered data?

    http://www.weil-mclain.com/products/display/18-Heat exc.

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  • hot_rod
    hot_rod Member Posts: 22,151
    nice solder work

    without a socket, like a fitting has, you don't have enough surface are for a soft solder joint to hold. Plus the movement while installing the HXers could break a soft solder joint.

    Even T-Drill joints with a shaoolw socket need silver soldered joints to pass code. Trust me I have tried soft solder on T-Drilled radiant manifold projects :)

    I like the Blockade cop-phos solder from JW Harris. Lower melt point but a strong vibration tolerant joint. Very easy to flow.

    I think your HX concept will work fine. It's all about surface area of the copper conductor in the fluid. I think you will have plenty.

    hot rod
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
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