Using Jetboil Flash Pot with Alcohol Stove

Quirk: Very nice little project. Thanks for posting it.

I'm often beating the drum about heat exchangers. If out for more than 5-8 people nights, you'll come out ahead. Even sooner with low-heat-rate stoves like alcohol burners. That's because the longer it takes to boil, the more losses you have to the environment off of the pot. Your project helps that in two ways: shorter boil time AND using the cozy to reduce losses of the pot sides. Plus, of course, you're extracting more heat from the combustion gases.

David,
– I agree about the importance of the Jetboil cozy keeping in the heat. At first glance, the cozy seems like a cheapo short cut for a pot handle, but does seem effective in keeping the heat in longer. I'm a eat-straight-out-the-pot kinda guy, so I like the pot insulation. I ate out of a non-insulated MSR reactor pot for 2665 miles once and found it cooled off too quickly. I imagine the Titanium pots are even worse.
– As for the heat exchanger on the bottom of the pot, I wonder if any benefits are more related to the maze of hot air-flow recycling around the surface of the bottom of the pot, rather than heat connectivity transferring from the extra metal to the metal closest to the water.
– My setup focuses the heat pretty efficiently on the pot. There isn't much hot air shooting up or out the side, nor does the support ever get very hot.
– Now that I've gotten past the basics of the penny stove mastered, (fitting the top and bottom snugly without tearing was trying my patience), I'm experimenting with different penny designs. Such as different burner-hole configurations and numbers. I'm getting close to a 0.5 ounce boil in 5 minutes. The insulated base does seem to really help with getting the primer time shorter, and quicker to consistent jet cooking which I'm shooting for.

I think the other variable that can make a big difference in this setup is the pot-to-burner height. I wonder what part of the flame hitting the pot is of optimal efficiency?

Quirk

>"As for the heat exchanger on the bottom of the pot, I wonder if any benefits are more related to the maze of hot air-flow recycling around the surface of the bottom of the pot, rather than heat connectivity transferring from the extra metal to the metal closest to the water."

Both stirring up the air flow and conducting heat through the metal fins helps. If you were going to primarily for the first effect, I'd call them "vortex generators" like on airplane wings and position them at an angle to the flow. I've found that to help on the vertical sides of a pot within a tight-fitting chimney/shroud. It would probably also help on the bottom of the pot.

> "I think the other variable that can make a big difference in this setup is the pot-to-burner height. I wonder what part of the flame hitting the pot is of optimal efficiency?"

Experiment with the pot being mostly out of the visible flame. More importantly, keep the HX fins away from the colored, bright part of the flame (let the flame burn and it won't oxidize the HX fins as much). Cold metal will "quench" a flame and that results in unburned hydrocarbons and more CO emissions – both of which are are bad. This is one reason we so often see low-to-moderate flames being more fuel-efficient than large flames.

Compared to most set-ups, I'd go with a little more pot height above the burner and I'd place HX fins near an outer diameter of the pot.