Aluminium or brass for heat exchangers?

[donradcliffe]

Originally Posted by Dave-Zim

Take a big earth moving machine for example,
One big radiator cools the water which is then pumped around the whole machine through various coolers. It cools the engine oil, transmission and hydraulics all in various oil coolers in a closed loop.
Why not the same on a boat?

Would like to hear if anyone thinks this a bad idea and more importantly, why?

As long as you want EVERY thing running 24/7, your idea will work.

[coastalexplorer]

Philosophically having one huge system instead of several small ones, Could mean that IF anything should go wrong with it to cause it to leak; you will have one huge mess of antifreeze coolant in your bilge.

Sure light weight is the quest of racers. However do cruisers out on the open ocean prefer a bit of weight on their vessel to dampen getting tossed around? An under loaded dinghy can be a dangerous experience in very rough water conditions. So does the same apply to larger vessels?

[Dave-Zim]

Originally Posted by Sailmonkey

Here's the big problem. At what temperature will you maintain the coolant water? That best suited for the engine? The generator? The air conditioner? An AC unit won't be happy with radiator water.


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That's a good question,

Depends on how it's plumbed.

I was thinking of having the refrigeration offtake first in the line because it needs the coldest coolant and in the grand scheme of things, doesn't make a lot of difference. Then the charge air cooler, then the AC and lastly the diesel engine. Diesels don't like running on cold water anyway to it would be fine at the end of the line.

A variable speed pump would take care of the flow rate. These are old technology, very reliable and also cheap. A spare pump carried aboard would take care of redundancy. Flow rate dictated by engine temperature I would think.

You wouldn't want anything plumbed in series. Parallel take off and return would allow flow rate for each device to be controlled by simply using a restrictor.

[Dave-Zim]

Originally Posted by Rustic Charm

I really don't follow this purpose at all. Some of the off the shelf units are both light and effective and cheap. And even if you are a bronze worker, making your own is just, 'why' ?

If your that concerned about weight, and your building a new solar vessel, then why are you putting a heavy diesel engine in it?

Agreed on the buy off the shelf units. It does make sense.
It's just that as I make them to put them on the shelf in the first place, It's nice to know exactly what went in to the cooler in the first place

The idea behind the solar powered boat is, when cruising in amongst islands or shore hopping where speed isn't an issue, the solar output will be more than enough to push the boat along at 6kn or so.
But, I want the ability to get a wiggle on if we need to run from a storm or any other reason while crossing an ocean. It's nice to be able to fire up a diesel and get the hell out of there. Will make me sleep at night.
There's a lot to be said for turning a key and opening a throttle when you need to

[Dave-Zim]

Originally Posted by donradcliffe

As long as you want EVERY thing running 24/7, your idea will work.

I speak under correction here but I would think refrigeration on it's own wouldn't need anything else running. Possibly the coolant circulation pump could cycle on and off every few minutes. Or, with variable speed pump, the pump could just idle along doing enough to cool refrigeration / AC.
Only when the diesel starts would the system really need to wake up.

[leftbrainstuff]

Originally Posted by Jsta_Rebel

I have a 130 Lehman in my boat. the expansion tank is cast aluminum. My copper heat exchanger failed allowing salt water to he circulated through the engine and of course the aluminum expansion tank. the expansion tank showed a lot of damage after 1 week of salt water exposure. I have photos for you to see for yourself if someone can explain to me how to post them in my posts. FYI, Heat exchangers use to be made from Navel bronze and lasted forever. The new heat exchanger I just purchased is nickel plated copper. I believe that this is the standard now.

Naval bronze is an old modification of brass to make it more corrosion resistance. Older heat exchangers built to this material spec often had very thick sections and were very heavy relative to modern heat exchangers.

It has good machinability and is now mostly used for marine interior use such as knobs and hinges.

I would not specify naval bronze for sea water heat exchanger use today. Many better material options are available now.

These days naval brass or bronze is often used as a marketing term. I wouldn't trust any product marketed as being made of naval brass.

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