allen lumley wrote:Xisca,and James : You both might like to look at the 'Homemade Mass Heater' Thread in the Wood stoves forum, as built, it is close to a good masonry stove
that a careful D.I.Y. Builder could follow, but still comes with problems getting the heat from the heater to your thermal mass ! Big Al !
james wood wrote:Wow! Thanks everybody for all the comments and help! These projects look like good fun! I very much appreciate being able to bounce ideas off you all.
I downloaded the book and have read the body of it – thanks! I am reading through it again a second time so it sinks in a bit better and I can converse more intelligently. There was indeed a place that talked about covering up part or all of the drum with cob so more heat would go to the thermal mass. But I do get the physics - that pressure increases in the burn tunnel as gasses heat up and expand and decreases downstream as that heat is lost on the drum’s surface. I understand that this creates the pump which seems to be an important part of the rocket.
I’m not sure how much a temp drop is needed and didn’t really understand the ram pump link. But I’m already thinking more intelligently about this! Woot! I’m also not sure how other types of fires differ (masonry vs rocket).
I’ll use some sort of clay or fire clay for the mortar.
Allen, you bring up something I have been thinking about – correctly sizing the heater to the greenhouse. I’ll be heating one of those 10 x 12 Harbor Freight greenhouses. They are “double walled” but my last one (sold with the house) was not sealed up very well. Unlike most people, I’m not trying to get a jump on spring planting. I live in S. Fl and want to be able to keep the temps above say 50F so I can grow some sensitive tropical plants to sell at local markets. And I’d like to use wood and other natural fuels (yard waste, we have an acre) if possible. One challenge is how big to make the heater. I really don’t want a huge thing that takes up a lot of room in the greenhouse. Something with a 55 gal drum is way to big. On the other hand, something to small may not scale well – it may not be insulated enough to reach the high temps needed for a full burn. I can use the floor as my thermal mass and save/double duty space there. I may be able to use the heater as a working surface when it isn’t in use. I certainly can easily find “urbanite” for thermal mass.
The new plan is to follow the books design but make something smaller that doesn’t have a huge footprint. How small?
Has anyone made a small one with a #10 can as the drum? Can you make a smaller rocket heater out of clay? Or will it heating up differentially cause problems? What it was made in parts that fit together?
The greenhouse will be very humid, will likely have fish tanks (thermal mass but will have fish in them so they can’t get to hot) and will likely also have a mist system. I know I can’t store the wood in there but had not given that aspect much thought. Since I’m designing the whole thing, it is good that you brought that up! Maybe I can build something on the back of the greenhouse and have the exhaust go by it to help keep it dry.