|
Post by getandistr on Jul 24, 2014 4:21:34 GMT -8
So I am just about ready to start construction on my rocket mass heater. I'm going to be using half barrels as a bell under my mass. With my current design I can fit 5 half barrels going along the bench and will be building an 8" system. I don't have any access to clay soil unfortunately as my property sits on a giant bolder and I only have about a foot of soil (none of which has a high clay content) before I hit stone. So I am now considering building a frame and using a dry fill instead. My question though is what can I safely build the frame out of to insure no issues with fire or degredation and what can I use as a fill?
|
|
|
Post by DCish on Jul 24, 2014 5:17:19 GMT -8
One way to add mass would be to just pile rocks inside the bell. It would increase your ISA, though, so you'd have to figure that in. And it doesn't solve the problem of how to cover the barrels. On permies.com I've read that loose fill tends to be more insulating due to air voids reducing conduction. Maybe you could haul in enough clay to use as a void filler between a bunch of rocks?
|
|
|
Post by matthewwalker on Jul 24, 2014 7:45:31 GMT -8
I've had good luck with hardiboard type products for the surround sheeting. For fill, I realize you are suggesting you don't have clay soil, but I still would recommend using what soil you do have, and the more rocks the better. Wet it down and make rocky mud. Fill with the rocky mud. Regardless of how much clay you have or don't, it will still flow and fill the air spaces and you will have a pretty sound monolithic mass. Since you are not using the fill as a structural element, the low clay content should not be a problem. I suspect there is a lot more clay in there than you think. If not, it will still work reasonably well and will be a good start. I feel like it will be superior to almost any dry filled mass full of air space, even if it doesn't have much clay.
|
|
|
Post by satamax on Jul 24, 2014 8:20:32 GMT -8
Well, why not use concrete? Full of big stones, so you don't spend too much on the concrete. 150kg of cement per cubic metre is plenty good enough for a rocket with the barrel holding the concrete.
|
|
|
Post by getandistr on Jul 25, 2014 4:37:16 GMT -8
How would concrete compare to cob in terms of heat storage? Also I remember reading before that concrete can't handle the heat it that only for around the burn tunnel and heat riser?
|
|
|
Post by peterberg on Jul 25, 2014 7:14:53 GMT -8
The magic word here is density. The denser, the more heat can be stored. And yes, normal concrete does contain a lot of silicium which changes christal structure around 500 centigrade if I remember correctly. That change is paired with rapid expansion, that's why concrete buildings can fail in the heat of a fire.
So it's not suitable for the hottest part of a rocket mass heater. You have to use refractory materials for that if your stove should last for more than a season.
|
|
|
Post by getandistr on Jul 29, 2014 4:51:13 GMT -8
That's good to know. Thanks Peter! Now what what being said how thick should the mass be over the top of half drums to still make it comfortable to sit on (I will have foton matressess over the bench for softness)?
Also I have some 2' x 2' by 2" cement pavers. My idea was for the bench area I could lay down rows of brick and put the pavers ontop to create an air gap under the bench. I was then planning to seal the gaps between the pavers with mortor. Do you think this will work or will the temp inside still be too hot for the pavers?
|
|
|
Post by getandistr on Aug 5, 2014 7:56:40 GMT -8
Anyone?
|
|
|
Post by grizbach on Aug 5, 2014 22:38:51 GMT -8
|
|