typical temperatures inside rocket mass heater

Hello,

i am working on my first RMH and am wondering about the temperatures inside.

I found information that temperatures inside the core can go up to 1000*C. But what about other parts of the heater ?
- what is typical max temperature at the top of the primary bell ?
- what is typical max temperature at the bottom of the primary bell (floor) ?
- what is typical max temperature at the top/bottom of secondary bell (bench) ?
- i found information that chimney temperature will usually go between 60-100*C

the reason i am asking is so i can better choose the materials:
- to isolate the floor. the heater will be build in the room with concrete floor, i don't want the heat escaping into it, so i want to build a proper insulation layer below the heater.  I saw how perlite can be used but i am worried about building on top of loose perlite so i would prefer to use something load bearing. I was thinking about using YTONG blocks covered by a layer of concrete made out of cement and perlite.
- to isolate the back wall of the heater and bench which is going to be build against the wall stone of the room. I was thinking about double skin bricks with a layer of ceramic wool in between them. I don't like it so much as there is still one layer of bricks absorbing the heat there. I was thining about using ytong blocks instead of bricks for the back wall of the bench, still doing double skin with ceramic wool in between. ytong blocks are ok up to 600*C, so i want to be sure temperatures inside my bench are not going to reach that level. I am wondering if i could do the same for the back wall of the primary bell ?

any other suggestions on how to insulate the floor and back wall ?

thank you.

Hi Peter, you don't mention what type or style of rocket stove you would like build?
Something like an 8” batchbox  is going to be a different animal to a 4” J tube, there would be  a massive difference in temperatures!
I doubt if many of us know what a Ytong block is but anywhere in the flame path you want materials that can stand at least 800c but better to use 1200 rated materials.
So we would need more info on your plans?

ytong blocks are aerated autoclaved concrete
i am building 8" batch box

Hi Peter;
With an 8" batch box you're looking at closer to 1100C  in the riser.
After leaving the riser things start cooling rapidly.
The top of the bell directly over the riser will be getting a direct shot of high temp air, I would guess that it could still be as hot as 900C when it hits your bell top.
The bottom of a bell should be near 65-85C but could at times be over 100C.
If you are building a bell rather than a piped mass then no need to extra insulate the concrete slab,  falling fly ash will cover the floor and become an excellent insulator.  
If you want extra insulation then you mix powdered clay and perlite with straw into a cob-like product.
Loose perlite alone is used to insulate between walls or between your mass and an outside wall.
A ceramic blanket is an alternative wall insulator, but much more costly than a sack of perlite.