If this is correct, could the preheat pipe actually be counter productive?
how big a factor is "cooler" intake air temps?
doesn't some wood stoves route intake air to pre-heat?
honestly guys, i have no idea how or why this stuff works. i likened it to the air injection system on older gm vehicles. cooler oxygen rich air was injected in to the exhaust manifold just outside the head. this resulted in the unburned hydrocarbons burning. why? how? i dunno! also reminds me of the 'bessemer process' in making steel. if you inject molten steel with cool oxygen rich air the contaminents burn off giving you purer steel.I think "cooler" is a relative term. The gases at the top of the firebox are anything but "cool" when a hot fire is going. The idea of preheating is so that the secondary air you introduce into the firebox is hot enough as to not self-extinguish the hot gases at the top of the firebox, and to promote a vigorous burn.
You've got it right. Also, I used the gate valves cause initially I thought I'd be regulating them partly closed, not leaving them wide open.I was thinking gate valves must have been used because they are often all brass where ball valves usually have seals that may not take high temperatures.
Yea, that's what I had in mind. The long run of pipe from the valves up the side of the stove and to the back before going into the burn tubes was to get as much preheating as possible. More preheating of the secondary air is better. The secondary combustion won't occur until around 1100 degrees. Cooler air will just quench the fire. I also aimed the jets toward the center of the stove instead of down for this reason though I doubt it would have mattered much which way they point. Most of the air probably exits toward the rear of the stove (at the beginning of the burn tubes). FWIW, I made the last 6 holes (the ones at the front of the stove) a little larger cause they were at the end of the run and would get less air. Also, since most of the air is going to leave the pipe at the beginning of the run, It has more time to mix and burn if the beginning of the run is at the rear of the stove.The idea of the small holes is to introduce good mixing of air with the volatile gases to get the combustion as soon as possible near the back of the stove; just dumping it out of the open ended pipes close to the baffle would likely burn it but that would happen further along toward the exit pipe so less heat gained.
I wondered about this too. Yesterday I measured temps at the same place on the stove pipe (my point and shoot IR thermometer doesn't go much over 500 degrees) at various times during the burn with the secondaries opened and closed. At no time did leaving them open decrease the temp. When they're working, the temp. increases with them open. When they're not working at the end of the burn, they have no effect on the flue temp.I think the biggest reason shutting down the secondary air to burn down a large bed of coals works is because the primary air is usually enters right at coal level. Secondary air most likely just cools down the fire box in coal burn down mode.
Just rambling off theories! Don't quote me.