Cooling of engine

Ove · Sep 17, 2011

Hi...
I am looking for a formula to calculate how much pipe I will need to remove a certain amount of KW in an outboard cooler.
Known data is how many KW I need to cool.
The water temperature.
Water flow in the cooling pipes.
Dimension of cooling pipes (outer diam. and wall thickness) and I nee dto calculate how many meter of a given pipe I will need to cool the given effect.

Can somebody help me with a formula for this ?

Thanks.....

TeddyDiver · Sep 18, 2011

A quote from old thread..

Originally posted by Apex1

Originally Posted by TeddyDiver
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..
Click to expand...

Make it easier Teddy (and safer),

as I said before, 100hp require 2m² in Alu, 6m² in steel, and that is what the engine manufacturers tell us (the industry).

A optimized flow* of the coolant, or tubes make a better result than a flat panel, of course.
*entrance of coolant is always at the aft end, forcing the fliud to flow against the seawater flow.
But both rules of thumb (Gerrs and ours) are worth nothing, when the area is calculated to the minimum, and one runs the engine for hours in warm waters at anchor.
Barnacles and marine growth do their part to make a minimal setup insufficient.
So, that should be done with a nice safety margin. Hence my larger figures.
And Gerrs "under 8kn" is a fault. It should be better saying at 8kn, because under 8 you slowly (pun intended) run into the insufficient range.

Regards
Richard
Click to expand...

A quote in a quote in a quote...
and the original thread in case you might enjoy how to bend it so to speek..
http://www.boatdesign.net/forums/diesel-engines/kool-keel-diesel-engine-34858.html

Ove · Sep 18, 2011

Keel cooling calculations

Thanks, but I was more looking after a way to calculate the heat transmission in a keel cooler. I also have a number of experience figures but I wish to calculate it with the real figures of heat needed to be cooled, water temperature, waterflow, dimension of pipes, wall thickness etc.

If any one can help me I would be grateful....
Regards
Ove

MikeJohns · Sep 26, 2011

Have a look here

http://www.boatdesign.net/forums/diesel-engines/keel-cooling-28061.html#post283527

http://www.boatdesign.net/forums/di...g-fresh-water-cooling-keel-cooling-21391.html

CDK · Sep 27, 2011

Ove, there is no formula because there are too many variables.
What you want to know is the thermal efficiency, expressed as delta t/ kW, for a heavily painted, barnacle festered keel cooler in a motionless sea. I'm afraid nobody can tell you that.

But you could use TeddyDiver's data as a starting point. 6 m2 for 100 hp translates to 0.08 m2 for 1 kW. That is approx. 1 meter of 1 inch steel pipe for every kW of the engine rating.

pistnbroke · Sep 27, 2011

and why would you want to do this on an outboard? if its that nasty impeller you dont like why not an external pump ? I can see how you can get the water into the outboard but how are you to stop it mixing with the exhaust ?

Mr Efficiency · Sep 27, 2011

pistnbroke said: ↑

and why would you want to do this on an outboard? if its that nasty impeller you dont like why not an external pump ? I can see how you can get the water into the outboard but how are you to stop it mixing with the exhaust ?
Click to expand...

I think he means outboard as in 'external', not an outboard motor.

pistnbroke · Sep 27, 2011

Yes I miss read it ..its the cooler that is outboard not an outboard cooler Dooh .....

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Cooling of engine

Ove New Member

TeddyDiver Gollywobbler

Ove New Member

MikeJohns Senior Member

CDK retired engineer

pistnbroke I try

Mr Efficiency Senior Member

pistnbroke I try

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