Post by flybyjohn on Oct 25, 2019 11:38:31 GMT -8
I have a batch box rocket stove in my garage with just a hot water heater tank as a bell over the riser designed for rapid heating of the garage. With the surface area of the steel tank and the firebox surround, I am getting a max of about 275 to 325 degrees F up out of the chimney pipe. I have built a sheet metal heat shield halfway around the tank to protect things on the sides and behind from the heat of the metal bell (it gets 800+ degrees F surface temp. near the top). This is offset 2" from the bell surface. I also have a metal shield on the top to protect the ceiling. There is a gap at the bottom of the shield and at the top to help air circulate through the gap.
I was going to put a duct in the middle of the back of the heat shield and attach a fan to blow the hot air through the gap and out into the garage. Right now I just have a big fan hanging from the ceiling blowing air though the space above the top heat shield and the ceiling and into the garage.
I was hoping that the addition of the fan blowing through the gap would allow more heat to transfer from the steel bell and lower the heat going up out of the chimney, (better efficiency).
So the question, Does blowing the hot air away from the bell essentially have the effect of having a larger surface area of steel bell? (reduce my exhaust temperature) Initially I was going to just add another bell to get more heat into the garage and less out the chimney, but space in the garage is at a premium and I don't have room for it. The fan would pull air from the floor and push it up through a 6" inline duct fan and through a 4"x12" rectangle duct attached to the middle of the back of the heat shield.