franco b wrote:I am not a fan of the bulk, but this is a prototype and not necessarily a finished design. It's to prove a point. It should lower stack temperature as well.
Agreed. If I were to build it again right now, I'd make the manifold shorter: more of a skillet than a dutch oven in size. Also would have designed the intake round from the start. I would compact the whole manifold. As for effectiveness, I can just tell from operating it that the air coming out of it is HOT. Much hotter than with a fan blowing on the stove surface. A few tests/measurements like you suggested and we could probably put together a model to prove some tangible benefit.
Also keep in mind I have one radiant and one fan powered floor vent/duct with a big heat collector above the stove: http://www.amazon.com/gp/product/B0085UZ8EK/ref=wms_ohs_product?ie=UTF8&psc=1
. So getting the hottest air up to the ceiling helps heat the upstairs better.