"James, I agree that surface area exposed directly to the flame is the biggest factor. Unfortunately increasing it via spirals or ridges would likely cause the price to increase by orders of magnitude. Vortex generators are interesting. That might be easier to apply. I wonder how crude they can be and still have a significant effect."
Eugene, Sorry about the delay, must've missed your post. Actually, it is realtivly simple with standard annealing and forming. I made several pots with deep ridges in the bottom and acheived an easy 15%-20% decrease in boil times, or, 15% less fuel for the same boil. Trail Design has those numbers. (My computer crashed and the new one lacks a proper interface for my backup tapes...someday...)
I simply heated the bottom of an aluminum grease pot, then pounded a series of ridges in it. To do it neatly would require tooling and a press, of course. I think I did something like 30-40 runs and and came up with an average, so the 15% is a pretty solid number. This works about the same in a cone as a larger pot. IE, the surface area of the 5-3/4" pot is about the same as the bottom surface area as a 6.5" pot, just concentrated.
This is all a heat exchanger does, BTW. I call the the ExPot...Exchanger Pot.
For a simple vortex generator at home, a ballpeen hammer around the outside will work. A series of smallish dents (about 1/32" or so) spiralling up the sides will work as well. The thought is to create turbulence without pushing the heat away from the sides to badly. I believe that you will find the cooler air layer is only about 1/16" thick, thickening as it goes up the pot. Perhaps 1/8" at the top. So you really don't need vortex generators, a simple dimple will work, spaced evenly about 10-20 dimples around the pots circumference. A small peen will work about the best for hand work. A continuous ridge will cause dead spots behind it, good and bad.
However, the vortex generators could also be used as heat exchangers around the sides and bottom of the pot.
More elaborate would involve a press twisted into it causing a slight helical ripple in the metal. Easily done with production tooling. Extraction might cause some difficulty, but a two step stamp, heat, twist/stamp should form it OK. Labour is cheap for this. Tooling is expensive. Anyway, the resulting pot, a cone/windscreen should be about $1USD or perhaps bit more to produce, rather than the current ~$.75.
Trail Designs rejected this stuff, soo, feel free...this is a patent free design.