Keel cooling design for electric inboard

Here is some good data of the Leaf motor at 50 to 80 kW (360Vdc).
The unknow data here is the coolant temperature, but the fact that the controller Cap temp stay in the 40 to 75°C range for the entire test let me think this is just above the coolant temp.
If I can reach 1/6 this power at 1/6 the voltage and 1/6 the RPM, that will be perfect.

 

I did a quick test to know how well regular 3/4 copper tube can be TIG weld on a 1/8'' copper plate.
Not too bad, so it's definitely doable.

So, the simpler design I could think of is to weld two 1/2'' NPT fitting to the 1/8'' copper plate and link the two fitting with a half tube.
Other option or better design?

 

That's not how it works. That would require 6 times the current of the stock motor/battery at full power! But I don't know what the derating rule is for this motor. I'd expect something more like 1/6 the power at 70% rpm, 50% nominal voltage, and 50% nominal current - but you need to find the actual curves for your motor.

 

I think I'm quite in control about this subject since I build a Dyno to test the Leaf motor at 48V and 60V. Details: Electric inboard motor, my journey to find proper motor https://www.boatdesign.net/threads/electric-inboard-motor-my-journey-to-find-proper-motor.69574/page-3#post-978187

Now I'm way more interested to have advices and tips about cooler.

 

yabert,

How many pages of this thread are going to be needed before you're done?
Perhaps a simple feed from a bow through hull is all you need, as suggested in post #4.

 

Probably I simply don't understand what you mean.
Do you have example?

 

Sure.
Install a large through-hull below the waterline in a high pressure zone of your bow
forcing water through a hose to your motor cooling jacket fitting.
Run a second hose from your cooling jacket exit to a low pressure zone through-hull in your stern.

Very, very simple.

Option: Install a temperature gauge at the cooling jacket exit to monitor your motor temperature.

 

salt water inside the motor. Sound like the worst possible idea.

With this idea, I could use a thermal heat exchanger inside the boat to exchange heat between salt water and motor coolant, but my goal is to have no salt water inside the boat.
To me it sound like a wise goal, no?

 

Great idea, use it to heat the cabin, this is "The Great White North"!

There would be no sea water in the boat.
It would be in the hoses and motor, if done properly.
Crazy idea I know.
Carry-on.

 

As I said in my other post, this isn't rocket science. Take a pipe, straight or bent into a U shape, stick it along the hull, let the motor coolant flow trough it. You can select the wall thickness to be enough to guarantee that even in the event of a collision the hull breaks before the pipe.
It works fine for thousands of commercial fishing boats cooling their engines, it will work for you too.

 

Not rocket science, but I can see here details who can lead to a good solution up to a garbage solution.
-Stick it along the hull: how to have a reliable solution?
-Across the hull: how to have reliable solution?
-What about marine life on this pipe?
-Copper corrosion in salt water: How to manage this?

Clearly it look like a solution who can work. But I'm looking for a solution who work well and reliably.

 

I've read a lot about SS316 in saltwater and it look like corrosion and biofouling can be problematic. Especially at weld joint/corner.
Add to this that SS316 is almost the worst metal to transfer heat and I've start to look to alternative.

I think I've find that yellow brass (brass 272) can be good candidate.
Seem to resist corrosion well, 10 time more heat conductive than SS316 and it available in affordable rectangular tube.
So, I design a small 6'' long, 2'' wide, 3/4'' tick cooler in brass 272.
Theoretically, it can eject over 15 000W of heat with a temperature differential of 20°C (coolant inside/water outside)
In think brazing or TIG welding could be challenging in order to don't have corrosion at weld joint.
Is there something wrong about my search or my design?
Advices about this brass solution VS SS316 solution are welcome.

 

There are thousands of fittings already made for copper pipe. They are readily available and fabricated for a proper fit. The box seems like a complication though. Attaching a pipe to the side of the hull is not too difficult. There are huge amount of workboats that use the setup successfuly. Many use a brackets over the pipe. Some have flat brackets welded on. Corrosion on copper is not a big issue. It is on the negative side of the electrolytic series. It will get green, but that is good as antifouling. If you prefer a box type cooler, a rectangular pipe would make the job easier. Otherwise, a pipe running along the hull, with a plate over it is a solution. The plate can be bent as a hat section with the flanges used to attach it to the hull.

 

Yes and everything should start with a bulkhead fitting to go across the hull.
It look like I will be able to use affordable standard bulkhead fitting to build a rectangular tube cooler (with a bit of modification).
This solution should be way more affordable than starting with 1''-8 thread rod to build bulkhead.

 

28:00 there's brass radiator raw water cooled .