Hi there!
This spring, I will build a
RMH in a small single-story, 75m2 house I am renovating in Slovakia (sorry for metric units

) I've heard so much about
rocket mass heaters, and here in Slovakia,
firewood is (relatively) cheap and abundant, plus I don't have a gas line in this house.. so in terms of both space heating, water heating and cooking, I want to take maximum advantage of renewables.
I thought: RMHs have been used in all three of those areas, so why not creating a kickass, all-in-one RMH, that would let me cook, heat the house and heat my shower & tap water in winter?!
So I came up with this quick draft, of a "
rocket mass heater cookstove heat exchanger":
I would really like to have your opinion on this design, because I have some doubts:
1. In my design, the firebox ends up having some sort of a heat riser over it.. that's not standard in the
rocket stove designs i've seen so far, although I have seen a similar design during my research (googling)(
Himalayan rocket stove). I don't know how this secondary heat riser could impact the stove's efficiency, or cause trouble with its "rockettiness", cause smoke issues through the feeding chamber etc...?
2. I'm not sure the oven could get
enough heat, without even considering the uneven temperature between the right side (against the steel barrel) an the left, by the exhaust, which could make uneven baked goods...
3. related to the 2nd question..: would the heat exchanger still have enough heat to exchange, after the fire has gone through so much heat losses, through the oven, and the two cooking surfaces? how would the placement of the heat exchanger be the smartest? around the exhaust as shown in the drawing? under the oven? inside the barrel, around the vermiculite heat riser (maybe too hot for copper pipes on the long run)?
4. On this design, the firebox must be very long (because of the cooking surface on top), compared to what I usually see in RMHs designs. is that a big issue?
I've read somewhere that when considering the length of the exhaust pipe buried in the cob, a rule of thumb for an 1/1.5/3, 8-inch pipe system, was to count 50ft of pipe, and subtract from it 5ft for every 90° elbows in the system. that sounds like a lot of cooling mass, so it seems like there's quite a lot of heat to extract from a RMH, which keeps me optimistic.. but I'd love to get your opinion!
I'm looking forward to your ideas and answers!
- Bruno