John Elliott wrote:These are all good questions and worthy of evaluating with some engineering experiments. But first let me ask you, why do you think that the RMH is losing too much heat up the stack? Is the exhaust gas temperature too high? The hotter the gas being evacuated to the outside, the more heat you could be trying to capture with some sort of fin or tube arrangement inside.
Then again, as the temperature of the exhaust gases goes down, you reach a point of diminishing returns in trying to capture those BTUs. The whole thinking behind hypocausts and long runs of pipe after the burn chamber is to allow plenty of time for the gases passing through to lose their heat to cooler surfaces. There are too many engineering factors to take into consideration beforehand in the design, so it's nice to have an after-build modification if you find that there is more heat to be extracted. At which point it's worth trying the things that you suggest.
allen lumley wrote:Strayz Arund : Todays 55 gal drums are made of a heavier gage (thickness ) than the Heat Exchanger on a conventional Fossil Fuel Fired Furnace (Air to Air )
these exchangers are usually rated for 20 years ! Here I should stop and recommend the 55 gallon drum with a top that is completely removable ! It makes
installation easier and though noticeably lighter it is still a thicker gauge than most F. F. F. F. Heat Exchangers !
With ` ~ 100,000 ~ R.M.H.s built there are many now approaching 20 years old w/ zero reported failures, this could be related to seasonal use,older heavier
55 gal drums, or other factors, but where are the reports of failures if they have happened !
Fins would be Great ! Before attempting any system that combines the Rocket stove and hot water heating, I would recommend buying and watching The
'Boom' 'Squish' DVD video offered here at Permies.com Big AL !