So I work at a nuclear power plant, and of an engineering mind. I noticed my UDS burned through considerably more fuel in the winter than in the summer....duh......right? Takes more energy to heat up cold air. Well, I've taken inspiration from the more efficient design of the reactor core, and applied it to a UDS. Here is what I've got.
Very simple. I've taken the intake pipes and put them inside the drum. This allows some of the waste heat that escapes the the sides of the drum to preheat the intake air prior to reaching the firebox. The cooking grate rests on the 90* elbows for the down pipes. 3 one inch holes are all that is drilled for the 3/4" pipes. No other holes in the drum.
I know, I know. "But it takes more energy from the fire to heat the incoming air.....The differential temperature of the air leaving, and air going in is what causes the flow. The incoming air will heat up and stop flow....."
First, the pipes are heated by waste heat that would leak outside the sides of the barrel. Second, basic heat exchanger physics is that none are 100% efficient. The air in the down pipes will be warmed, but never reach cooking temps. Third.......we use the same design to make a nuclear reactor more efficient. If it's good enough for a power plant, it's good enough for my smoker.
Right now, the smoker is lit with no meat load on it. It's cruising at about 280*f. This is the WFO temp. I'm gonna monitor it every hour until the temp dies off. results to come.
My only "if" is that 3 three quarter inch down pipes might not be enough air flow. I did that to eliminate the chance of a 'teetering' cooking grate, and 1" pipes just looked too big. I'll be loading this thing up to max capacity (4 butts) this weekend to check performance.
I now leave it to the forum to poke holes, ask questions, and make design change suggestions.
My only request is that IF this works, you put StuBByQ somewhere in the name.