Technical - Firebox Design


The JUCA firebox has many obvious features. It also has some that are not so obvious.

First of all, in free-standing JUCAs, the back wall has a slight curvature to it. That helps to re-direct some of the heat radiation of that wall back into the fire, to help maintain the necessary heat there for most complete cumbustion. The curvature also allows the back wall to expand and contract with various heating conditions with ever making any "oil-drum" sounds. Finally, that curvature also affects the dimensions of the rear plenum chamber, which helps move the room air in that chamber to where we want it for most efficient heat recovery.

The firebox side walls also have a very slight curvature designed into them, for basically the same reasons. They are also tilted at a 17 degree angle. This aids in the geometry of that re-radiation mentioned above, but it also improves the geometry of the walls heat capture in the first place, too! The radiation from the fire impinges on the wall surfaces at closer to a NORMAL angle. This statistically reduces the reflected heat component, which leaves more to be transferred to heating the metal of the wall, which slightly enhances the heat transfer efficiency.

It turns out that the heat capture and the succeeding conduction, convection and radiation (to both sides) is virtually irrespective of the color of the wall surfaces, since it is the so-called "black-body" radiation. Therefore, painting the inside surfaces of the firebox walls (a process we once believed to be important) turns out to be irrelevant as to maximal performance.

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