Hot water and hot air

[GILow]

Gas is NOT lighter than air. That’s why it is such a problem on boats.

[Shaneesprit]

Originally Posted by noelex 77

Some of the drip feed diesel heaters such as the Reflex brand produce great heaters, but they will also produce hot water. This can be done in two ways.



KISS. This requires a kettle to be placed on hot plate on top of heater, or slightly more complicated with a copper coil inside the heater.



The only drawback is these heaters can be difficult to retrofit. There are specific requirements for the chimney installation as well as minimum clearances from some surfaces.



Here is a photo of our installation, taken during construction of our new yacht, to give you some idea:

This solution I like but as you said it maybe hard to retrofit into my space unless I redesign the interior, which would be possible as a late 1980s 6 birth would be better as a 4 birth with lots of room - not sure where I am going but I brought 2 systems to see what the fitting options are

[wingssail]

Originally Posted by Shaneesprit

...Gas is lighter than air and I have an alarm fitted...

Sorry, for propane, the fuel which is easily available everywhere in the world, that is not true. It is heavier that air which is why so many people shun it. (it can collect in the bilge and ignite).

I, however, do not worry about that so much. My nose is good at detecting gas. If I am not there, or asleep, the gas solenoid is off and no gas can enter my boat. In 33 years we have not had any worry or dangerous situation.

[wingssail]

Originally Posted by noelex 77

Here is a photo of our installation, taken during construction of our new yacht, to give you some idea:

Beautiful installation! However, in my experience the change of air pressure while sailing in ocean swells will cause the fire to blow out. Heaps of smoke in the cabin. Adding a 6ft smoke stack outside will help but mostly you'll need to shut it off while sailing.

[timb7734]

We have a Webasto diesel unit in our 22 foot RV that makes hot water and heat both, has been very reliable and economical

[tjsailing]

We have a Planar deisel hydronic heater with the option to circulate the heated coolant through the boat - that line is conected to 3 blowers. We can also have the water on a loop only to our hot water tank - takes about an hour to heat a 6 gallon tank to about 30 celcius which is perfect for showers, dishes. The planar system is a russian design originally made to heat truck cabs - was about 1/7 the cost of other hydronic systems. We have been really happy with it. As the hose running through the boat is only 5/8" thick it was easy to run through with minimal damage.

[Shrew]

Originally Posted by GILow

Gas is NOT lighter than air. That’s why it is such a problem on boats.

Well, except: hydrogen, helium, neon, nitrogen, ammonia, methane



Obviously using the word "Gas", which is a state, to represent an element is oddly confusing to begin with (i.e. "which gas").

But yes, the vapor you would potentially find on a boat (Gasoline, Diesel, Propane, butane) are all heavier than air.

[GILow]

Originally Posted by Shrew

Well, except: hydrogen, helium, neon, nitrogen, ammonia, methane



Obviously using the word "Gas", which is a state, to represent an element is oddly confusing to begin with (i.e. "which gas").

But yes, the vapor you would potentially find on a boat (Gasoline, Diesel, Propane, butane) are all heavier than air.

I should have expected this. I mean somebody already told me I had misused the word furnace.

[RaymondR]

Originally Posted by GILow

I should have expected this. I mean somebody already told me I had misused the word furnace.

You're having a bad day mate.

I suspect Ammonia is heavier than air but wouldn't bet on it and don't care enough to check.

[GILow]

Originally Posted by RaymondR

You're having a bad day mate.

I suspect Ammonia is heavier than air but wouldn't bet on it and don't care enough to check.

Well, there are certainly a few heavier-than-air gasses around the forum at the moment. H2S comes to mind.

[pbmaise]

Hmmm.

My diesel tank has a recycle line.

If I used a solar heater during the day to heat up my diesel fuel I would have a large heat sink which could be used to heat hot water and the air.

No the diesel would not be burned to heat the water or warm the air. The hot diesel is just circulated through a heat exchanger.

[GILow]

Your diesel tank is insulated!?

[pbmaise]

Originally Posted by GILow

Your diesel tank is insulated!?

Actually it was. My former vessel was composite epoxy core and it would have insulated warm diesel well against cold exterior water. Not perfect but still a potential heat sink large enough to store solar heat generated during the day. There would be some heat lost to the interior of the vessel, however in winter that would be fine.

Excess engine heat could also warm the diesel tank just as it already does since the diesel warms already owing to fuel recycling.

That brings up another creative idea. The engine block, radiator, oil, and all the containers of oil in a typical engine room represent a large thermal mass which could store excess solar heat generated during the day. Running radiator fluid into a solar heater and around the boat to various heat exchangers would be less hazardous than running fuel lines.

Since saving weight is key to the OP and adding thermal solar panels may not be practical, running the engine could be the source of heat that is then stored and distributed around the vessel.

As I relate this to my former vessel I realized I already had the extra pump and fuel lines to warm diesel fuel tank. My high speed fuel polishing system could have circulated fuel to be heated/cooled.

[GILow]

I’ll give you credit, it’s good lateral thinking.

But not much good if you want to use your diesel to say... motor somewhere.

[Dockhead]

Originally Posted by GILow

I’ll give you credit, it’s good lateral thinking.

But not much good if you want to use your diesel to say... motor somewhere.

Indeed. And one more fly in that ointment -- diesel fuel has specific heat 2.5x less than water, and is lighter per volume. So you'd need probably 1000 liters of diesel to hold the same amount of heat as maybe 350 or even less of water.


Storing heat is a great idea -- not just solar heat from day time, but imagine how much heat you could pull out of main engine waste heat while motoring.


But I can't think of much of any good way to do it. Lead keel comes to mind, but lead has specific heat of like 35x less than water so even 8 tonnes of it doesn't amount to much heat storage.