I was just reading some posts at the garn site,and one post that caught my attention was that the heat exchanger inside the garn is 60' of 6" pipe. Is this true or were they just messing around ? If it is true, where is the most heat taken from, the pipe or the firebox submerged in the water? Would 60' of pipe take off that much heat from fast moving air?
Garn heat transfer to water
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No idea about your question, but it brings up an apparently good feature about the Garn. Anything that gets heat is against water, so the metal gets minimal stresses. Hence, they last a long time.
Wade,
The primary firebox doesn't get hotter than any LARGE wood fire would, with a forced draft, I don't believe. There are 5 passes
(about 10' each in my 2000) of heat exchange pipe
(5" boiler tubing) between the primary fire and the flue-pipe exiting the boiler. The first few feet of the flue passage after leaving the primary firebox, is a ceramic lined secondary burn chamber that can get up over 2000F. By the time those hot gases reach the exit, they are never more than 200 degrees above the water temp, so I'm told. Sounds kinds funny, but if that "fast moving air" that you speak of is actually white hot gas moving through a tube in 150 degree water (or less), that's going to give quite a nice heat exchange I would think.
Guys here, that have them up and running, all say how fast the water temp rises during a burn, so I guess it works, although I can't say first hand.
The primary firebox doesn't get hotter than any LARGE wood fire would, with a forced draft, I don't believe. There are 5 passes
(about 10' each in my 2000) of heat exchange pipe
(5" boiler tubing) between the primary fire and the flue-pipe exiting the boiler. The first few feet of the flue passage after leaving the primary firebox, is a ceramic lined secondary burn chamber that can get up over 2000F. By the time those hot gases reach the exit, they are never more than 200 degrees above the water temp, so I'm told. Sounds kinds funny, but if that "fast moving air" that you speak of is actually white hot gas moving through a tube in 150 degree water (or less), that's going to give quite a nice heat exchange I would think.
Guys here, that have them up and running, all say how fast the water temp rises during a burn, so I guess it works, although I can't say first hand.
This is a cross section drawing of the Garn.
(broken link removed to http://garn.com/content/performance.aspx)
The Garn is an awesome boiler by all accounts. I have crunched a lot of numbers and for various reasons the Garn is not going to work for me. If things were different I wouldn't hesitate to buy one. I really like the concept.
Noah
(broken link removed to http://garn.com/content/performance.aspx)
The Garn is an awesome boiler by all accounts. I have crunched a lot of numbers and for various reasons the Garn is not going to work for me. If things were different I wouldn't hesitate to buy one. I really like the concept.
Noah
The Garn was a no-go for me unless I wanted to build a separate outbuilding or addition for it- but it really is a brilliant design, and I have yet to hear of an unhappy user.
Wade said:
Wade - yes, there is over 50' of boiler pipe that functions as the primary heat exchanger in the tank of the GARN. It is a well designed, highly efficient system (both combustion and heat transfer).
i am not sure if the hx tube dia was changed, my model 1900 has 4 passes at 4 inch dia and the last pass at 5 inch dia. and a 6 inch interface to class A flue.
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