Keel cooled engines?

[ted655]

When cooling a diesel of around 100 hp. , can a keel cooler be as simple as a pipe full of antifreeze mix, tucked up around the keel? Running up one side, looped and running back. One inlet, one outlet. Is there a balance valve or restricter of some type to regulate the flow/temp so proper heat is maintained? Can this pipe be bolted to the "inside floor or sides" of the keel, or must it be exterior, "in contact" with the water", using thru-hull fittings?
Is there a formula for sizing the diamator, length of the pipe? 2" black pipe, corossion painted about right?
I always hear of this type cooling, never saw one. I've seen heat exchanger type but am wanting something more simple, (no pumps, thru-hulls, bypass hoses, etc.
Thanks.

[sal's Dad]

First: you posted this in the Metal Boat Building section - but don't say - do you have a steel hull?

If so, you can run your keel cooler through internal "half-pipes" welded to the inside of the bottom. These can be structural members, and so serve double-duty. Many people put them on the outside, but I can't figure why - it increases wetted area, resistance, bottom maintenance, vulnerability to damage.....

On the other hand, if you are talking about fiberglass or wood, you will have to get the cooling pipes outside of the insulating hull.

Yes, there are "rules of thumb" as to sizing, generally so many square inches of exposed surface area per HP. This will, of course, depend on your usage, water temperature, etc. As I understand, bigger is NOT always better.

There have been a number of threads on this topic, here, and over on the Metal Boat Society forum; but it's midnight; too late for me to dig up the links.

Sal's Dad

[ted655]

Thank you. Yes it is a metal hull. A channel form, welded along the bottom would do the trick then.
I will dig deeper in the archives and look for more posts.

[SamSam]

Originally Posted by ted655

Thank you. Yes it is a metal hull. A channel form, welded along the bottom would do the trick then.
I will dig deeper in the archives and look for more posts.

Or angle stock would work also. Sam

[MikeJohns]

better if it is split RHS or just rectangualr channel and in contact with the exterior plating . there is a fair amount of heat to dump. Channel can replace the stringers but the mass is not so important down there.

We have covered this before.

Otherwise simple cheap heat exchangers can be fabricated from pipe in a pipe type construction but you still need to pump the seawater.

[bertho]

Mike,
as you look fully aware about this keelcooling, give me your input:
i saw some system with 2 differents keelcooling for one single engine, one we run with lower temp,for the aftercooler, another one for the engine, as the temperature is higher to keep sufficient flow for pump cavitation problem. is some other system to avoid to send too cold water for main engine cooling?
and keep aftercooler efficient?

[MikeJohns]

Bertrand

You can simply use a common thermostat system. Just think of the way an automobile cooling system works and replace the radiator with the keel cooler. The only pump is then the engines main coolant pump. If you use an external pump and you are worried about cavitation you need a more complex setup with temp monitor and automatic bypass valve etc.

Best to keep things simple as possible as it gets more complex always try to fit an overtemp and cooling water loss alarm.

[bertho]

Mike,
I fully agree to do simple but...my understanding was the water cooling engine on the standart system, with coolant/ RW water cooler, don't go strait on the bloc, just through the cooler (water/coolant), can be cold, as sea water 20/30 deg celcius, and can be use directly for the aftercooling exhanger (water/air), but with keel cooling, this coolant go directly inside the bloc and engineer said is not good to have cold water going strait in the bloc at 95 deg.. and the same coolant, is too hot to be efficient for aftercooling exhanger water/air.
following you arguement, water on a radiator is not as 20 deg!
this explanation was acceptable for me, but if you have 2 main engine with aftercooler, and 2 genset with aftercooler , the result under the hull is... crazy! 8 differents tubing system!
that why i try to find somebody to convince me !
cheers