Keel as Heat Exchanger

[kloudie1]

Casper, these guys might have some info .. they may have even made one or two:
http://marskeel.com/technology/1
Scott's observation on cross section weakening in the keel is the reason I suggested embedded tubing which essentially does not affect the cross section if designed and positioned correctly.. No question that the void would work.. as would the embedded tube..
Interesting.

 

[kenn]

I'm not an expert in keel casting technology, but it's not rocket science, I doubt casting a void, with two fittings stretches it.

I'll let a casting expert have the last word on this, but I suspect that simply casting-in a sealed void, or fabricating and casting-in a prebuilt copper cooling 'coil', (my choice) would both be considerably more expense and work, and have a higher reject rate, than simply casting a simple keel, whose only requirement is to be 1) mechanically solid and 2) heavy.

The raw water cooling "system" is the weak point in today's marine diesel engine technology. Ever price a Yanmar heat exchanger?

I worked for approximately 3 months for a yacht diesel shop, servicing Yanmars, Volvos, Westerbekes, Universals etc. Between you and me, I think the entire inboard power-plant and drive-train of the average yacht leaves alot to be desired. Snag one rope and you're replacing shaft, motor-mounts and maybe the strut. Routine replacement of motor-mounts every 3 to 5 years, which means wrestling with the engine to achieve mating to the coupler with less than 4 mil gap on the face. Crank an unresponsive engine for too long without closing the raw water intake... hydro-lock the engine. And so on...

After work I used to come home and hug my reliable, easy to maintain 5hp 2-stroke outboard, knowing that if it ever failed utterly, I could replace it with another used one for about $600

Ok I actually love the little diesels themselves, but you can see from the above that a heat-exchanger is not top of my list for weak points. Also, heat-exchangers will have a long life with simple filter protection and regular maintenance.

Does a cast lead keel present enough surface and have enough volume to function as a heat exchanger? Absolutely. But I think this thread has clearly identified enough valid reasons for why it isn't done on production boats.

 

[sea_casper]

Still, Why Not the Keel?

Casper, these guys might have some info .. they may have even made one or two:
http://marskeel.com/technology/1
Scott's observation on cross section weakening in the keel is the reason I suggested embedded tubing which essentially does not affect the cross section if designed and positioned correctly.. No question that the void would work.. as would the embedded tube..
Interesting.

Nice site, it looks like the casting technology exists, and people are obviously doing more complex things to keels.

Tubes are less efficient if embedded siince the heat transfer is to the sides of the keel, it would take a lot of tubes to equal a single thin slot. If we consider a thin (1/6m) ~6" wide U shaped slot of a total length of (2m) ~6 ft, would have 1 square meter of transfer area. if it was 1/8" thick it would have the same cross section area as the 1"I.D. raw water inlet hose of my engine. I do not believe that would compromise the keel strength in any significant way.

Also as I posted out in my original posting, the keel is a good place to mount a flat plate exchanger on a side or both sides, a better place than on the bottom of the hull as is sometimes done on power boats. If the side of the keel was designed with a cutout to accommodate it, a thin metal flat plate exchanger would be more efficient at heat transfer. and would be replaceable. Overall more expensive than designing one into the keel.

Google "keel cooler" or "keel cooler images", and you will see a bunch, none of which actually are part of a keel, which is my original question, why not the keel?