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Old 04-18-15, 05:33 PM   #1730
AC_Hacker
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Quote:
Originally Posted by Spiv View Post
...One of the motors is coupled to a small heat exchanger and supply hot water to the 23lt electric water storage/heater.
I have no means of heating the boat while I waste so much heating energy every time I run one of my three diesel engines.

All that heat is wasted, I could have boiling water using a heat pump!

I have not been able to find a DIY heat pump construction, lots of commercial ones.
I would like to use some recycled parts from perhaps fridge, air conditioner or car/truck heat exchanger. Or a combination of them.

Do you know of efficient ways to recover heat from those motors, perhaps heating water that I can circulate through the boat to heat it?
Any ideas/ links would be very much appreciated.
Stef,

Thanks for your post.

Regarding heating, heat pumps are best suited to harvesting 'low temperature heat' and raising the quality (temperature) up to a level where it is suitable for applications like room heating or domestic hot water. Due to the physics of the refrigerants, going much beyond 120F or even 140F is not in the cards, unless you go with specially designed compressors and other components and use CO2. Even then the max temp would be around 160F.

So, a good use of a heat pump might be, for times when you are in port and have shore power, to harvest the low temperature heat from sea water and elevating the temperature to heat the interior of your boat... but boiling soup would not be an option.

As you mentioned, the wast heat from your engines is considerable, and as dremd suggested, directly using that heat via a heat exchanger is your best bet. If your cooling system is under pressure, your circulating water might even be a bit over 212F.

The temperature of a gas or alcohol flame is something like 3400F, which is considerably higher than 212F, and it enables us to boil water in the prompt manner, to which we have become accustomed.

However, elevating the heat that cools an engine to the point where you could boil water would be really tricky, and I am not aware of a well known technology that would do this for you.

There is a possibility that a completely new type of heat pump could be designed that would use a special refrigerant that could do it's change of state in the temperature range that was well above 212F... in the 2000F to 3000F range

Your post definitely points to a technical problem that to my knowledge, has never been successfully addressed.

If this problem could be solved, I believe that it would open up a whole new technical field and market.

-AC
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