Graham Chiu wrote:A bell I believe just refers to the container of the gases. So, if you had a double wall with the gap holding the gases, then that's still a bell.
Jim Higgins wrote:Thanks Graham. I understand the concept of the bell being just a chamber holding the gases. The problem for my intent is that all the heat is kept at the top of the bell while the cool air is at the bottom. I need the whole wall to be warm. This is why I believe I will go with ducted space whether that is via metal duct work or simply building duct space with the brick or other material I end up using. With the duct work, at least as I understand now, all heat travels the entire duct work, thus heating the mass all along the way. If the ducted spaces progress upward instead of around and back (however many times) in a low bench, the heat will build up from the bottom to the top of the wall where the exhaust will exit and go through the roof. If my understanding so far of the premise behind the ducting principle is wrong, I would appreciate some explanation. Since I have not yet read the work books available I realize I may be blowing smoke ;-}