Most efficient windscreen for remote canister stove

[Jon Fong / Flat Cat Gear]

To boil 2 cups of water (68 F to 208 F) using 4.9 grams of fuel means that the efficiency is ~70%.  That is a highly efficient system.

(sorry, cut and pasted from Excel)

Isobutane 45.2088 J/g
Fuel consummed 4.9 g
Total energy available 221523.12 Joules
M*Cp*DeltaT
2 cups of water 473 g
water 4.186 J/gC 4.186 J/g°C
Start 20.0 C 68 F
end 98.3 C 209 F
Energy Required 155098 Joules
Efficeincy 70%

 

If you believe in math (which I do)

Boiling the same 2 cups of water using 2.0 grams of fuel means that your efficiency is 172%.

Math is fairly predictable.   My 2 cents.

 

P.S. there is a simple test for this as well.  At 100% efficiency, the exhaust air temperature should be the same as the ambient air temperature.

[bradmacmt]

Boiling the same 2 cups of water using 2.0 grams of fuel means that your efficiency is 172%.

Math is fairly predictable. My 2 cents.

I’ve dinked around with enough stoves and pots to know that 2g of fuel usage boilng 16oz’s of H2O isn’t something I’ll ever personally see :)

[Roger Caffin]

172% efficiency does seem bit unlikely, doesn’t it?
Even 70% stretches my credulity somewhat.
I normally work on 50% max, for most any gas stove.

Cheers

[Jon Fong / Flat Cat Gear]

70% is pretty high.  That being said, a number of JetBoils can reach that level of efficiency in dead calm conditions so it is doable.  The initial calculation that I did were for both @bradmacmt and @Ken Larsons’s postings.  Like a JetBoil, these are two finely tuned systems.  My 2 cents.

[MJ H]

Boiling the same 2 cups of water using 2.0 grams of fuel means that your efficiency is 172%

Propane-induced, low-heat fusion reaction.

[DAN-Y]

The stove used in my favorite kit is operating at it’s maximum efficiency. Air fuel mix is at maximum efficiency. Valve opening is at 1/2 power. Pot supports have been modified to allow stove burner head to be at maximum efficiency distance to pot bottom. Diameter of stove burner head is such that it concentrates heat to the aluminum pot bottom which is the most efficient metal for heat transfer for backpacking pots. 30% greater efficiency is achieved right off the bat with the exchange fins on the pot. The greatest efficiency increase comes from the heat exchanging windscreen that closely surrounds the pot. Starting water temp is at 70 degrees, calm conditions and full canister of fuel.

[bradmacmt]

Starting water temp is at 70 degrees

I don’t think I’ve ever boiled 70* water in the mountains. That’s the reason my test it with 53* H2O.

[Jon Fong / Flat Cat Gear]

Starting water temperature doesn’t mater when calculating efficiency.  Heat transfer is heat transfer.  A colder start temperature does reduce the test variability, however; this can also be done by replicate testing.  My 2 cents.

[Roger Caffin]

70 F water in the mountains?
Most of the year the water in our mountains is more like 40 F!
YMMV
Cheers

[DAN-Y]

I don’t do mountains

[Jerry Adams]

similar to Dan’s

aluminum flashing

#18 galvanized steel wire on the outside to compress the windscreen against the pot for better heat transfer and to keep it from falling off

the exhaust gasses mostly go between flashing and pot.  Some of the heat goes to the pot.  Some of the heat goes to the flashing and is then conducted to the pot

1/2 inch folds in the flashing

1.25 ounces

maybe 10% savings in amount of butane used

I think you need some sort of windscreen on a canister stove and this is about as light as it gets, plus you get some heat exchanger functionality

I think this would work on a remote canister stove

windscreen removed

[Roger Caffin]

Hi Jerry

It’s a nice idea, but I can foresee or imagine some problems:
Looks like a bit of faffing around to get the corrugate shield set up around the pot
How do you pack the thing into your pack without damage?

Thoughts?
Cheers

[Eric Blumensaadt]

The Old Reliable MSR heavy, folding aluminum windscreen works just fine for this geezer.

And it’s easily tailored to suit yer needs.

[Bonzo]

I don’t do mountains

Blasphemy…😉

Looks like a bit of faffing around to get the corrugate shield set up around the pot. How do you pack the thing into your pack without damage?

I assumed it was shorter than the pot and just nested inside…am I missing something?

[DAN-Y]

Nice blue flame expending maximum efficiency to bottom of pot. Four modified pot support legs transfering heat to bottom of pot, not to fins. They get red hot and transfer directly to aluminum pot bottom.

[Jerry Adams]

windscreen stores inside pot

To assemble, take windscreen out of pot, place the two hooks in the wire together:

Then, put the windscreen onto the pot. It’s sized to barely fit onto the pot, sort of springy.

If you put your 4 ounce butane canister inside the pot, you could put the windscreen outside of the pot, and put that into the bag, and that would contain the windscreen.

[Jerry Adams]

faffing?

I get my education on British/Australian slang here : )

[Roger Caffin]

I get my education on British/Australian slang here : )
And it is 100% FREE, too.

[Chris R]

I made a copy of Jerry’s windscreen. No faff. It’s possible to connect the wire loop, I used stainless fishing leader wire, and then push the pot down into the screen. Works extremely well.

[Bonzo]

I made a copy of Jerry’s windscreen. No faff. It’s possible to connect the wire loop, I used stainless fishing leader wire, and then push the pot down into the screen. Works extremely well.

I kind of want to try one of these and connect the two ends with a pair of captured springs; it wouldn’t be appreciably better than the wire bail, but it would be fun to do and it should work pretty well.  Bonus points for sizing the gap to work with a pot handle? 🤔

[Roger Caffin]

Photos Bonzo, photos!

[Bonzo]

Give me a day or three to work on it; can’t seem to find my 1.3L pot right now…

 

[DAN-Y]

Nice blue flame expending maximum efficiency to bottom of pot. Four modified pot support legs transfering heat to bottom of pot, not to fins. They get red hot and transfer directly to aluminum pot bottom.

2 cups boiled, 2 grams fuel used. Too bad the Sterno Inferno pots were discontinued, I could have sold a million with such good efficiency.

[bradmacmt]

Starting water temperature doesn’t mater when calculating efficiency.

I get what you’re saying, but it takes longer to get 53* H2O to boiling than it does 70* H2O. That goes to fuel usage, no? My point was, when someone claims 2g’s fuel usage, it’s probably not something I could replicate with a 53* H2O start as with my tests.

[Bonzo]

I get what you’re saying, but it takes longer to get 53* H2O to boiling than it does 70* H2O. That goes to fuel usage, no? My point was, when someone claims 2g’s fuel usage, it’s probably not something I could replicate with a 53* H2O start as with my tests.

It does require more fuel to do that, yes, but that doesn’t change the efficiency.  It changes overall consumption, as you noted.  And no, you probably couldn’t replicate that with your test at 53°, nor would that be a replication of the results: one variable would be changed from the outset, so your results would be under different test conditions.

[Author]

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