how about a cheap, self contained, seawater cooled HVAC?

Discussion in 'Boat Design' started by Squidly-Diddly, Sep 10, 2016.

  1. W9GFO
    Joined: Dec 2014
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    Location: Olalla, WA

    W9GFO Senior Member

    I can imagine a well intentioned DIYer holding his hand to the water output and feeling that it is warmer, declares that he has made it more efficient.
     
  2. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    The whole point of a thermostat in automotive applications, is to keep the engine in a desired temperature range. Without it, the coolant eventually goes well out of range and this isn't good for any engine. There's a number of things that can also occur, with it removed and one of the bigger concerns is what happens when you decelerate (shock cooling). Modern engines will try to richen the mixture, because sensors are justly telling them the engine is cold and a host of other issues. So, what you end up with is an engine out of temperature range, out of air/fuel ratio range and suffering from other cooling related issues.
     
  3. W9GFO
    Joined: Dec 2014
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    W9GFO Senior Member

    Yes, and at a somewhat high temperature where it can operate more efficiently. The narrow temperature range allows for the engine to be built to closer tolerances. An air cooled engine by contrast must have higher tolerances for the wider operating temperature range.
     
  4. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    Agreed. I work with a lot of air cooled engines and just the valve lash clearances are telling, compaired to liquid cooled engines.

    It's interesting you mention "high temperatures" as this was a relatively recent revelation. For several decades 160 degrees was the standard, but with more machining precision, more precise fuel delivery and engine controls (timing, ignition, etc.), ideal temperatures have risen 10% - 15%, permitting leaner mixtures, better efficiency, etc.
     
  5. FAST FRED
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    Location: Conn in summers , Ortona FL in winter , with big d

    FAST FRED Senior Member

    "It's interesting you mention "high temperatures" as this was a relatively recent revelation. For several decades 160 degrees was the standard, but with more machining precision, more precise fuel delivery and engine controls (timing, ignition, etc.), ideal temperatures have risen 10% - 15%, permitting leaner mixtures, better efficiency, etc."

    On modern 18 wheel trucks the new standard is 235F by using a special coolant.

    A 2 or 3% difference in fuel burn is u$eful when running 6MPG for 200,000 miles a year.

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  6. stinkydog
    Joined: Jul 2016
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    Location: michigan

    stinkydog New Member

    Primary purpose of the thermostat is to get the engine up to operating range, not keeping it cold. Keeping the engine around 200 degrees improves efficiency, 'boils' out any contaminants (acids, condensation, blow by etc) and improves oil action.
    As mentioned earlier, if a thermostat is removed, it can cause overheating problems because of the engine design. Some engines use the thermostat as a restrictor or to direct flow, but on more typical engines the only result is that the engine will take forever to reach operating temps on a closed system, and never on an open raw water system.

    If you want heat transfer don't use restrictions, you want more flow with a large surface area. If using the hot water/baseboard heat units shown earlier (tube and fin) you will want a fan to keep air moving and some way to drain condensate.

    Edit:

    I've thought of using a deep cooling system before, one design I came up with was to use a closed loop. A couple long reinforced flexible tubes you can let down, with a 6 inch by 18 inch coil of copper tube at the end. would allow using clean water to eliminate possible clogs, and if you sprung a leak in system you'd only have the fluid in the loop to worry about.
     
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