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Old 07-04-2016, 08:29   #16
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Re: Aluminium or brass for heat exchangers?

you really should stick with off the shelf coolers, there are plenty to choose from and you will never make them yourself.
nothing is simpler than a keel cooler....but the outside type are vulnerable to damage...the type which are like a simple tank inside the bottom couldnt be simpler but cant be added to an existing frp hull if that is what you are using.
a "common (or LT) cooling system" circulating fresh water somewhat similar to what you describe is precisely how it is done on many ships. you will find it adds weight and complexity, you still need the coolers on each equipment but you have to add another cooler and circulating pumps which will now become electrically driven. there are redundancy issues so usually the pumps will be duplicated. You also will have to use a dry exhaust.
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Old 07-04-2016, 08:52   #17
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Re: Aluminium or brass for heat exchangers?

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Originally Posted by Dave-Zim View Post

And the second part...
Understood, but for now I'm really only asking if the concept sounds plausible. Why would running the boats cooling requirements in a single closed loop be a bad idea?

Dave
With one single system you have one point of failure. If that point fails, you are SOL. No generator cooling, no refrigerator cooling, no A/C cooling.

With multiple systems, you have multiple points of failure, however, it becomes less likely that all will fail at the same time. Additionally, you could install a manifold that would let you by-pass a failed exchanger.

In sailing, especially in more exotic places, redundancy is a good thing.
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Old 07-04-2016, 09:00   #18
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Re: Aluminium or brass for heat exchangers?

you could try titanium.
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Old 07-04-2016, 09:01   #19
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Re: Aluminium or brass for heat exchangers?

Why re-invent the wheel. I purchased an oil cooler from Lenco. Good people to work with & a solid product.

Lenco Coolers - marine heat exchangers, marine oil coolers
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Old 07-04-2016, 10:01   #20
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Re: Aluminium or brass for heat exchangers?

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Greetings all

I want to design new heat exchangers. These will be mounted inside the engine bay with raw water pumped through one side and fresh water / antifreeze / glycol pumped through the other side.
I want to make them out of aluminium for weight saving but I'm worried about how long they will last. Brass / bronze would be best but the weight is putting me off.
Does anyone have similar exchangers made from ali and can tell me how long they've been in service? Any problems with accelerated corrosion?

Thanks in advance

Dave
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.
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Old 07-04-2016, 10:03   #21
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Re: Aluminium or brass for heat exchangers?

No question about it titanium is the best material for a heat exchanger, but it's tricky for small engines. To get the same heat transfer the tubes have to be very thin, which is fine from a strength stand point but difficult to fabricate. If you have the experience this is a good way to go.

The other option is to buy a commercial pool heat exchanger. Many of them these days are titanium because it is immune to the chloride attack in pool water. Just look for the ones with a transferable lifetime warranty against corrosion.
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Old 07-04-2016, 10:07   #22
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Re: Aluminium or brass for heat exchangers?

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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Old 07-04-2016, 10:17   #23
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Re: Aluminium or brass for heat exchangers?

The Yanmar in my HC38 had an aluminum heat exchanger/header tank that was not affixed to the engine but mounted alongside. One area failed after 14 years... right at the fitting where the hose connected. Frankly I wouldn't worry about the weight at all.
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Old 07-04-2016, 11:01   #24
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Re: Aluminium or brass for heat exchangers?

There is also off the self stainless steel plate heat exchangers that are inexpensive.

http://www.amazon.com/350-000-BTU-30...heat+exchanger

Only issues are it can clog and be near impossible to clean without acids. But for the price, buy two and have one for a spare.
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Old 07-04-2016, 15:33   #25
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Re: Aluminium or brass for heat exchangers?

My boat has two stainless steel heat exchangers to cool the engines using raw sea water. The water is pumped through with two brass pumps driven by the engines.
The engines are cast iron of course.

The only issue so far is the stainless tend to crack due to different expansion rates in the hot and cold parts.

These are commercially available and comes with anodes fitted. The anodes last 3 months and is the pin type that screw in. Fortunately easy to reach but you need to know where to look.
Hope this helps. The heat exchangers definitely do not corrode but need attention occasionally.
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Old 07-04-2016, 15:44   #26
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Re: Aluminium or brass for heat exchangers?

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Originally Posted by Sailmonkey View Post
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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This is what I see as the main issue. Use a sea chest and then you can take off at for at least 2 heat exchangers. One for the stuff that likes it hot and one for the things that need to say as cool as possible.
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Old 07-04-2016, 16:15   #27
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Re: Aluminium or brass for heat exchangers?

Has anyone heard of or had experience with plastic ??? style lots of new cars use plastic??? header tanks on their radiators. I question my description of plastic I use the term loosely.I am thinking of the outer tank being an Industrial hot water pipe cut to size and end caps screwed with the tubes ( copper) inside, raw water run through the tube as normal,anyone done it.
I have seen oil coolers on harvesting machines which use hydraulics to run their functions. Air is not practical as there is too much " fluff" and it clogs up the cooling fins.I am sure someone has tried it.
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Old 07-04-2016, 16:46   #28
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Re: Aluminium or brass for heat exchangers?

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?
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Old 07-04-2016, 17:04   #29
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Re: Aluminium or brass for heat exchangers?

The big guys are using titanium.Price is down. Titanium will last indefinitely,but it can cause galvanic corrosion to your less noble components,if done wrong.

Titanium hardware
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Old 07-04-2016, 21:32   #30
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Re: Aluminium or brass for heat exchangers?

Is it weight or labor you are trying to save. you loose a few ounces with aluminum and add a few pounds with an extra pump and fittings and piping/tubing. Not to mention what has already been mentioned about loosing all systems if one goes out. if its the extra through hull below the water line us a sea chest. You also have more electrolysis by adding another dissimilar metal, so you'll be changing anodes more often.

I've learned that some of the best design engineers are the ones that work in the field first I've taught a few of them when I used to build simulators. once they got over the fact that I don't even have a high school diploma - i was the lead mechanic and all my crew were collage edicated ;0)- they saw thing quite a bit differently....like where the human hand can fit ;-) among other things.

BALANCE is the most important thing for a well made boat. If you only look at a small part, you can do some pretty ingenious things but still loose the balance.

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