Specific Heat vs Conducitivity: Moving a stock tank into the Hermit Hut - for both Thermal Mass and washing facility: Concrete Pavers also?

The water itself will have way more thermal mass than your cob (about 3 to 4 times as much by volume) so you shouldn't need much masonry if you can insulate and weatherize it.

 https://permies.com/t/29699/RMH-livestock-water-winter

 So one of the three stock tanks for the mushroom water - is this 74 gallon sheep stock tank.

You could even stage a pot of hot water on top of the barrel, with a tap on the side to drain it into the tank and heat things up that much faster. You shouldn't need more than a 30 to 45 minute fire if you are dumping hot water in directly to mix with the cold in the tank.

So the idea is that I would get the wood stove going to heat up water and then pour it into the stock tank - for a bath. I can keep adding more water to store the heat. Then take a bath. Then the water will radiate the heat through the night. I can then keep the water in until I need another bath and in the mean time the well water will recharge (as it is slow to recharge enough water).

  I'd be tempted to rig things so you get a little more heat into the building from it and just use the hot water from atop the barrel to heat the stock tank. Make a warm spot the stock hang out in, and they may also serve as thermal mass / buffers to reduce the heat loss and keep their water thawed.

 Yes precisely - so I would be just like "stock animals" in this thread on the Permies forum. I have created an insulated shed - and I warm up the stock water and so the building has heat from the stock water that radiates - and it keeps me warm.

So let's say I heat up 30 gallons of water. Each gallon weights 8.34 pounds. So that's 250 pounds of thermal mass which is three times more than clay thermal mass - so that is the equivalent of 750 pounds of clay!

Therefore, one brick weighs 6 pounds

So 750/6 means the water is the equivalence of  125 bricks. I have already over 100 bricks in the hut for thermal mass.

So there is an offer to remove free concrete pavers - that I could also use as thermal mass. How does that compare to clay?

For concrete, figure on about 0.2 btu per pound per degree F.

Ie - 0.2 btu x 5 pounds per paver x 15 pavers x (heat them to 200F, cool them to 70F = 130F difference)

0.2 x 5 x 15 x 130 = ~2,000 btu's of heat ...about as much as you'll get burning 1/4 pound of wood.

https://www.hearth.com/talk/threads/pavers-for-thermal-mass.27034/

Snow falls but no need to shovel - due to Thermal Mass of the concrete!

https://greenpassivesolar.com/passive-solar/building-characteristics/thermal-mass/

The back of the house has wood instead of concrete - so need to shovel the snow!

 Per pound water stores 5 times more heat than rock (the density of
rock offsets this difference to some degree). One BTU will raise the
temperature of one pound of water one degree F. To raise the temperature
of rock or adobe requires only 1/5th of a BTU.
thats 80% less

 https://permies.com/t/2657/rocket-mass-heater-water-thermal

fascinating. So water stores more heat but it's more difficult to heat up...

Kind of makes sense. So the idea is by having the water directly on the stove - it heats up faster and then you dump the water into the stock tank as stored heat....

I know concrete is not good ecologicaly, and is not as cheap as clay, but it is a better heat tranfer material than clay or cob.

hmm - I was thinking concrete was more of an insulator! Oops.

Oh I remember now - I am thinking of ELECTROMAGNETIC insulator.

 It is also a gigantic heat transfer surface to the ground,
which is usually not desirable.

So what's funny about this is that I WANT direct connection to the Earth for electromagnetic conduction (not insulation!).

 I used crushed gravel and compacted it, just like i do when building roads or laying base for a patio or concrete. despite being professionally compacted, the air gaps in there are still insulative. There is a youtube video where one of those expert RMH builders tried to use fine sand as the mass. Conclusion is that there is just too much air space for good thermal conduction. So I had to scoop out the whole mass and mix it with a clay slip. Tamp down any air pockets. actually for mark II, I laid in a layer of clay slip and gravel, then laid in slabs of granite. It's like a lasagna. The results were immediate and pronounced (once it all dried).

The mass must be __monolithic__.

So they key for the rocket stove mass heaters is that the duct pipe is buried in clay - which has NO air space - and therefore the heat is based on conduction 100%.

http://digital.bnpmedia.com/publication/?i=127948&article_id=1193042&view=articleBrowser#{%22issue_id%22:127948,%22view%22:%22articleBrowser%22,%22article_id%22:%221193042%22}

Wow - no cut and paste? That's serious html mojo.

So based on that analysis - concrete outperforms brick BUT water is more conductive due to convection in the water!!

So water has 5 times more "specific heat" so therefore it can store more heat per volume but brick and concrete need 4 times LESS heat to conduct the heat back or radiate it back out.

 Ok so that's the difference between specific heat and conductivity. Fascinating. It's pretty subtle.