Keel cooling design for electric inboard

[gonzo]

It is simple. Run a pipe along the bottom/keel intersection. If you want it more streamlined, weld a plate of hat section over the pipe, which also makes it easier to attach. The pipe can either be bent at the ends to enter the hull or 90 degree elbows soldered to it.

 

[yabert]

Run a pipe along the bottom/keel intersection. If you want it more streamlined, weld a plate of hat section over the pipe, which also makes it easier to attach. The pipe can either be bent at the ends to enter the hull or 90 degree elbows soldered to it.

Clearly I would like to see pictures, because when I read this I only imagine horrible design.
Many tight space for marine life to grow, seaweed to fix. Bended pipe who apply lever on the bulkhead, screws/fixation problems... really, I've hard time to imagine something nice.

I think I've found C11000 copper rectangle tube (40x20mm) on Ebay (china supplier).
That would allow me to build this little 6'' long copper cooler able to transfer over 30 000W of heat with only 20° C temperature difference between coolant and water.
So, two 15$ brass bulk head fitting + 70$ copper tube, that sound an affordable cooler solution to me. I need two.

 

[BlueBell]

My point is to find the most reliable solution instead of the most simple.

Funny thing is, the simplest if often the most reliable.

Page 7. Carry on.

 

[fredrosse]

"I think I've found C11000 copper rectangle tube (40x20mm) on Ebay (china supplier).
That would allow me to build this little 6'' long copper cooler able to transfer over 30 000W of heat with only 20° C temperature difference between coolant and water."

Remember that while the thermal conductivity of Copper is excellent, but the overall heat transfer for the cooler consists of several thermal resistances in series, and these resistances form the limits of heat transfer See my previous post on this subject. In fact, Copper or stainless would work virtually the same here, even though the Copper has thermal conductivity several times higher than stainless steel. The 30,000 Watts of heat dissipation on a small surface area you mention at 20 c temperature differential seems far too optimistic.

The system of a copper pipe "keel cooler", as Gonzo suggests is common in hobby steamboat practice, where steam engine exhaust steam is condensed. This typically is a large heat load, and running the copper tube along the keel, somewhat protected from groundings, is common practice.

 

[yabert]

In fact, Copper or stainless would work virtually the same here, even though the Copper has thermal conductivity several times higher than stainless steel.

I thought that copper underwater will be less prone to biofouling and that eliminate the most important thermal resistances of the series of resistance. No?
The 30 000W of heat transfer with a 20°C of temperature difference is probably optimist, but it give me an idea that I will be ok to transfer 1000W-2000W of heat (my needs).

 

[fredrosse]

As posted previously, there are in general 5 thermal resistances in series, and each contributes to the overall heat transfer resistance. Biofouling may, or may not be the most important thermal resistance, Sea side convection coefficient and fresh water side convection resistance are generally dictating limits on the thermal performance, and these facts very often make it such that the conductivity of the metal, being pure silver, copper, or stainless steel virtually does not matter.