Starting the next build. 220mm batch rocket, double bell.

[patamos]

Satamax,

I was reading up recently that 1 cubic pound of sand has the same specific heat capacity as about 3 gallons of water. This is from a fellow on the east coast of US named Bob Ramlow, who builds 2ft deep insulated sand beds and pumps hot fluid through it from solar hot water collectors via hydronic tubing.
Sand probably has fifteen or twenty times slower rate of conductivity that water has (due to air pockets), but then most earthen materials are about 10 times slower. I think if you fill those bricks with dry fine sand you will gain a fair bit of harvesting mass for very little cost/effort

[satamax]

That could be a good solution for the back wall. The bricks around the tank will be filled with "grout" more or less. Thanks a lot for that Patamos.

[Deleted]

Nov 3, 2015 22:57:32 GMT -8 patamos said:

Sand probably has fifteen or twenty times slower rate of conductivity that water has (due to air pockets),

It is rather in the range of 2-4 times and with an ideal distribution of particle size from coarse to fine
the difference could be very small, maybe even better than water.
Water is a rather lousy conductor.

[satamax]

Thanks a lot guys.

Now it's mater of finding a way to stuff sand into that wall!

Anyway, i've made few mods today.

Goten rid of the air entrained concrete top. It was broken. But the surface was still real tough.

So my opinion on the stuff. If it's not load bearing, it could be used for the sides and bottom of the batch box, the same way as i've built it here, even without refractory protection. Just the two slants made of refractory. And it would certainly cope for a while. That would be intresting for prototyping.

I've replaced that top by cast iron plate, well actualy two. Given by a friend today. Fitted the door on hinges. I have slightly more primary air than needed, but since the air takes two bends to reach the firebox, that might be all righgt. Mind you i have 79.45 aproximately. It's a gap on three sides of the door. The top being closed by the original ruber seal from the door.

And i have lenghtened the slants to 3cm from the door. So now i could fit 55cm long pieces of wood.

The cast iron top can't boil water at the first burn of the day i wouuld think, if i don't put lots of sticks. But it could most certainly cook stews.


Also, on the second burn, when i had lenghtened the slants. I filled it two thirds, or thereabouts, with long pieces. And it has that lovely purring sound, quite strong, but not pulsating, well behaved. It seems to work well. I was expecting less of a rumble than that. After Peter's comments about last year's pyraunt's event big batch.

[patamos]

It's looking good Max

Karl, i am confused. I have always been under the impression that water is the ultimate thermal conductor to which all other mediums of dense mass are compared. Can you offer more explanation?

[Deleted]

patamos, if you have ever got very hot soup you should know the answer from own experience.

The thermal conductivity of Water is only 0.58 W/(m K) which is rather low,
but it can easily be moved around and has a high specific heat.

[pinhead]

Nov 4, 2015 21:47:24 GMT -8 patamos said:

It's looking good Max

Karl, i am confused. I have always been under the impression that water is the ultimate thermal conductor to which all other mediums of dense mass are compared. Can you offer more explanation?

Specific Heat is what you're thinking.

Specific Heat is a measure of the amount of energy a substance can absorb per degree temperature rise. In other words, if you dump the same amount of energy into a pound of water as a pound of sand, the sand will be "hotter" (higher temperature) while holding the same amount of heat energy.

[satamax]

So, i tried to boil water.

Well, withg a stainless steel pot, it took about 30 to 40 minutes to boil one liter. Ney good! Tho, that's on the first burn.

[patamos]

Thanks Karl and Pinhead.

So the common saying in the world of hydronic heating: 'Water is the ultimate conductor'… is a bit askew from the precise definition of conduction. The rapid wicking away of heat from an object by water is due to its mobility. Water molecules move along once warmed, cool ones come in to replace them and exchange with the warmer surface.

I think this broader definition of conduction has been used in some of the literature. Ken Mastez's book comes to mind.

When discussing parameters such as thermal emmissivity, absorptivity, specific heat capacity… conductivity etc… I am pretty sure i have seen water toping the charts in all categories.  Then again, my memory can be a bit porous...  


Satamax, have you thought of cutting away a preferred size hole over top the heat riser and recessing a pot into it? Maybe a larger permanent pot with vendable lid. Easy hot water supply ala Donkey's experiments.
And great specific heat capacity

[satamax]

Nov 5, 2015 19:14:35 GMT -8 patamos said:

Satamax, have you thought of cutting away a preferred size hole over top the heat riser and recessing a pot into it? Maybe a larger permanent pot with vendable lid. Easy hot water supply ala Donkey's experiments.
And great specific heat capacity

Too late! There's 265kg of mass there now!

[Deleted]

Nov 5, 2015 19:14:35 GMT -8 patamos said:

 Water molecules move along once warmed, cool ones come in to replace them and exchange with the warmer surface.

The hot soup shows that the water molecules can not move enough to have a significant effect.
You can eat hot soup from the edge of the plate or the surface,
but you'll burn your tongue if you try it from the ground in the center.
If you heat water in a pot the heat travels mainly by steam.
The Oceanic circulation is mainly driven by increased concentration of salt, not temperature difference.

[patamos]

Thanks Karl.

My learning continues…

I remember a factoid from studies in kinesiology that: 'water draws heat away from our bodies 30 times faster than air'. In other words, one will lose heat 30 times faster immersed in cold water than the same temperature air if unclothed. If facing hypothermia in water it is best to keep still as the movement will accelerate the heat loss. Water may not conduct heat through its mass all that fast but it can be moved around, which is why it is so useful as a way of transferring heat via hydronic circulation.

Likewise, moving air (wind) will also accelerate heat loss. And sitting on a cold rock will also drain heat via conduction… but these are less effective processes due to less than complete surface are of contact. Water takes the shape of any object.

Anyway. Just reflecting on the new information.

Back to Satamax's topic. I'd be curions to see how much faster the water boils in an aluminum, mild steel or cast metal pot.

(Edit - apologies for side tracking the thread) (and thanks always for the education)

[Daryl]

Nov 5, 2015 11:56:07 GMT -8 satamax said:

So, i tried to boil water.

Well, withg a stainless steel pot, it took about 30 to 40 minutes to boil one liter. Ney good! Tho, that's on the first burn.

That is a bummer.

[Vortex]

I think the reason your water's taking so long to heat up, is because the batchbox port is sucking the flames out the back into the heat-riser, away from the water. Most stoves built for cooking that work well have some kind of channel that draws the flame through a gap under the cooking plate.

[satamax]

Nov 6, 2015 15:51:16 GMT -8 Vortex said:

I think the reason your water's taking so long to heat up, is because the batchbox port is sucking the flames out the back into the heat-riser, away from the water. Most stoves built for cooking that work well have some kind of channel that draws the flame through a gap under the cooking plate.

Well Trev, this is an ongoing experiment. I know that the best way for heating water is direct flame, above the heat riser for example. Like the range rocket retrofit. I boiled some water fast enough for my needs last night, at least i think. I'm pretty sure i could cook stews and the like on it. For the rest, it's working rather well for my liking.