time
New Member
Posts: 32
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Post by time on Mar 8, 2015 3:17:29 GMT -8
Hi
I hope you are able to help. I've had several fantastic experiments with the Rocket stove concept. I'm now happy to invest in something larger to provide radiant heat for an outdoor area.
I have plenty of wood offcuts to burn so fuel usage is not a large problem, particularly as it will be fired only once per month or so when entertaining.
I was thinking of building a 10/12in rocket with refractory brick batch box and insulated perlite riser. Nothing too challenging there. but i have no idea how to size the bell or bells. My idea is to use a long thin bell 500x2000x4000 with mostly masonry construction but with "iron windows" that would act as radiant panels.
I would like to hear peoples thoughts on this and if anyone has a bell calculation formula i'd love to know it!
Regards, Time.
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Post by satamax on Mar 8, 2015 3:52:02 GMT -8
Too large a bell i would say!
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Post by peterberg on Mar 8, 2015 4:35:04 GMT -8
Hello Time, welcome to the boards. Max is right, that bell is way too large. A batch box wth a 15 cm riser could serve a masonry bell of just short of 6 m2, that's what we know for sure. A riser of 20 cm cross sectional area is about 1.7 times as large as the 15 cm riser. Calculated this way, the bell for the larger system could be 1.7 times as large, so that would be 10.6 m2. I've done such a system of mixed bell and bench construction, most of it metal, and it still worked like a true rocket with about 9.5 m2 internal surface area. Taking this a bit further, a 25 cm riser system is 2.7 times as large as the 15 cm system. And would be large enough to probably serve a bell of 16.6 m2.
Calculating a bell is done in internal surface area (ISA). All the surfaces except the floor should be accounted for. Since I don't know how thick the walls of your bell are I assume this size to be internal. That would end up with 20 m2, way too large for even a 25 cm (12") riser. Mind you, a 10" system is already like heavy artillery, I seriously don't want to know how a 12" system would behave.
So it would be best to calculate a smaller bell I would say.
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Post by shilo on Mar 9, 2015 11:22:58 GMT -8
you can simply do 2 6" heaters. much more comfortable to be between 2 heat sources.
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time
New Member
Posts: 32
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Post by time on Mar 20, 2015 18:15:53 GMT -8
OK Thank you all for your replies. I have refined the idea and moved to a smaller 160mm system. The ISA for the Bell is now apprximaltey the size of 3 barrels. Does anyone see any issues with this design? Also, do you think i will have problems with the masonry cracking due to the expansion of the radiant steel plate? My Idea to to run the Primary air in horizontally, and the P Chanel vertically through the bell to hopefully get some reasonably heating of both the primary and secondary air. Also, having the flue run though the bell should allow additional draft? Attachments:
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