kool keel diesel engine

Discussion in 'Diesel Engines' started by carlos bairo, Sep 28, 2010.

  1. Landlubber
    Joined: Jun 2007
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    Landlubber Senior Member

    The engine in question is only 20kw anyhow, so it will work very well....
     
  2. apex1

    apex1 Guest

    Lets go back where you started.

    The keel is insufficient in most cases to be the cooler, because the flat plates don´t provide enough surface for efficient cooling in adverse conditions. Maneuvering is such condition, when you have no speed, but power demand.

    The thermostat opens progressive, yes. It does not "shock" the engine with a sudden action.
    But again, the keel is insufficient, hence no shock at all, because you cannot overcool the system. The opposite, you would cook it to death.

    Regards
    Richard
     
  3. singleprop
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    singleprop Junior Member

    Let me use an example, 5 degree sea water, 20HP engine, 5 sq meters of keel surface area and 500 liters of cooling fluid. Surely, this set-up will result in the return water temparature being the same as the seawater temperature. I would expect that even 30 degree seawater would result in 30 degree return water to the engine.

    Thanks for confirming the slow opening and closing of the thermostats.
     
  4. apex1

    apex1 Guest

    20HP ?

    well, that is a new point of view for me. Of course that will easily be handled inside your keel.
     
  5. singleprop
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    singleprop Junior Member

    Yes,, that was the point I was trying to get accross when saying that the cooler was way way way too big...
    Anyway, what do you think would be the HP limit for a setup like this? I'm guessing that even 50HP and 30 degrees seawater would result in seawater temperature return water.
     
  6. apex1

    apex1 Guest

    Difficult to estimate without knowing the conditions you sail in.

    If the cruising ground is warm and you go usually at slow speed, those 50 hp can already be the maximum with your (theoretical?) keel setup.

    In the Baltic at high speeds the 100hp might be the max.

    Do not underestimate the influence of speed! Even the flow of coolant is important. When you do such a keel installation, make sure the warm coolant enters at the rear end and goes back at the front end. That maximizes cooling when both liquids run the opposite direction.

    Regards
    Richard
     
  7. Landlubber
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    Landlubber Senior Member

    Carlos asked "i like to know if it's better to fit the engine (kubota 28hp diesel)", now that little sucker can simply use a built in double bottom lengthwise section instead of cooling pipes, I have done it up to 45 hp on a Daihatsu in a 34 foot boat, carlos is building a 7m boat.
     
  8. Landlubber
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    Landlubber Senior Member

    Our seawater max temp for Sydney area is never above 25 degC, so all is well for the application required.
     
  9. cthippo
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    cthippo Senior Member

    Is there a general equation for area of cooler vs HP or KW?

    Does coolant flow velocity make a difference?
     
  10. TeddyDiver
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    TeddyDiver Gollywobbler

    Dave Gerr advices about the following in the Boat Mechanical Systems Handbook:
    For a steel boat, painted bottom, displacement speed under 8kn. Seawater temp up to 29C (85F) 0.037sqm/bhp equals (0.4sqft).
    With 28hp you need ~1.04sqm of keel cooler area (I rounded up a bit some..)


    As a rule of thumb, -with aluminium the area is half of the steel area and with copper half of the aluminium area..
     
  11. cthippo
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    cthippo Senior Member

    so .4 sqft/hp roughly?
     
  12. TeddyDiver
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    TeddyDiver Gollywobbler

    For painted steel 6 to 9mm thick yes..
     
  13. TeddyDiver
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    TeddyDiver Gollywobbler

    Yes it does.. however it runs by in the engine inbuilt pump and varies by the rpm so you can't do much about it. Much more influence makes how the seawater flows around the keel cooler..
     
  14. carlos bairo
    Joined: Dec 2008
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    carlos bairo Junior Member

    hi mate thanks for reply,i am building a tug boat alloy for a pleasure only
    hull speed-6.8knots /21'6''overall-beam-8'2''/draft2'9''/displasement@dwl5850lbs/engine sould be a beta 25hp-prop-18''x10''shaft-32mm/kooling area=3.6mt along the keel i have choose a marine engine due to continuos duty insted
    of marinaising a tractor motor.a dry exshaust sistem with a stak that will be
    isolaiting the exshaust pipe of 2''diam x a 10''diam stak .
    my cuestion is sould i need?heater exchanger?-if no't a thermostate to control
    the kooling temperature,theare so many diferents oppinions on this topic
    best regards CARLOS
     

  15. michael pierzga
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    michael pierzga Senior Member

    Carlos , Sketch your proposed installation and post for more accurate advice. Also if you have small commercail fishing craft in your area, have a look at their solutions. Fisherman dont waste money on gizmos and their gear works, Keel cooling, dry exhaust , marinized tractor engines...all typical on fishing boats.
     
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