Feb 4, 2012 at 8:02 am #1285156
It was 29F.
Using a 1/8th full canister, it slowly fizzled out before it heated a cup of water.
Switched to a full canister and it worked fine.
Put this on the 1/8th full canister:
The tip of the aluminum was in the flame and the whole piece got hot to touch.
The canister was not really noticeably warm.
I used the canister to heat a couple pints of water. Worked fine.
This is a good alternative to inverted stove in cold weather.
1/2 ounce. 18 gauge galvanized steel wire. Fairly thick aluminum, like for flashing.
I bet this would work down to 20 F. You'de have to warm it in your pocket before starting.
Obviously, you have to put your hand on the canister and if it gets warm to the touch, turn it off before it explodes.Feb 4, 2012 at 1:06 pm #1834428
@rcaffinLocale: Wollemi & Kosciusko NPs, Europe
Can I suggest 2 improvements?
1) shape the aluminium to fit the canister better: that gives better heat flow
2) use some serious compression on the strip – something like a hose clamp or maybe a cable tie pulled hard.
CheersFeb 4, 2012 at 1:22 pm #1834431
Good ideas Roger, I'll try them next time
This was sort of quick and dirty : )Feb 4, 2012 at 9:13 pm #1834649
The Complete Walker IV has an illustration of a similar method using wire and pieces of spring (p. 312). I've found that just a one or two pieces of wire wound around the stove from pot support to canister bottom is enough to make a real difference in canister performance. 12 or 14 gauge solid copper wire is easy to form, cheap and does an excellent job. The canister does not get noticably warm, but the wire itself does get hot enough to make it very uncomfortable to touch. If you just make a loop of wire that goes from the top of stove to under the canister, there is no attachment needed to the canister, and heat transfer seems to be sufficient.
JimFeb 5, 2012 at 12:39 pm #1834863
2 feet of #14 copper wire weighs 0.4 ounces. That's enough to wrap around cannister and up to flame. I'll have to try that next time. That's a little easier to make and put in my cook kit…Feb 7, 2012 at 8:23 am #1835717
Aluminum will be a better performer for the weight (by a factor of about 2) — assuming you get it thick enough to not melt.
Will have to try this out.
thanksFeb 7, 2012 at 7:09 pm #1836035
I ran 3 single lengths of 17gauge Al wire from my stove flame to a small cup of room temperature water (20grams total).
Over about 10 minutes the temperature of the water increased ~7.5F or 4.2C. I calc a heat transfer rate of about 35J/min or about .5W.
I will look into 10gauge wire…this should increase the heat rate for a single strand by about 5X. I am thinking about 2 upsidedown "U"s hanging from the pot supports (6 total U's) — With the 12 wire legs sitting in a water bath for the canister. Should give ~1000J/min or 17.5W.
I typically operate the stove at ~1gr fuel/ minute. Heat of vaporization of the fuel requires about 350J for a gr of fuel. Therefore I need to add about 350J/min or 6W to the canister to keep its temperature constant.
It seems this would provide a good bit of margin (about 12W) to cover heat loss from the water bath to the air and ground. More testing to come……Feb 7, 2012 at 7:51 pm #1836058
Daryl and DarylParticipant
@lyrad1Locale: Pacific Northwest, USA, Earth
Thanks for the info.Feb 7, 2012 at 8:56 pm #1836080
One thing that's not obvious is how much heat is transfered from wire to canister. There's a pretty small area of wire touching the canister.
There's good heat transfer from wire to water.Feb 7, 2012 at 9:27 pm #1836093
@b-g-2-2Locale: Silicon Valley
In the old days, we used to use this wire method to deliver a bit of warmth to the gas canister. We used a couple of feet of the heaviest copper wire that we could find, which was generally 12 gauge or 10 gauge. We used a heavy hand sledge to mash the wire onto a smooth concrete slab. We were not trying to mash it to be wafer thin, but just to flatten it halfway so that more of it would be in contact with the canister. We generally had an inch of it right next to the flame, and the bottom end of it had a couple of wraps around the canister.
It never seemed to hurt, but it was hard to tell exactly how much warmth it actually delivered.
–B.G.–Feb 7, 2012 at 9:57 pm #1836098
"it was hard to tell exactly how much warmth it actually delivered."
With my aluminum strip I'm pretty sure it made a big difference.
Without strip it faded to nothing before I heated up one cup of water. With strip I boiled a couple pints, although it was slower than if it had been warmer.
The strip didn't have good contact with canister – I think a wire wrapped around it would have been similar – now I'll have to try it, except I might not have very cold temperature again this winter.Feb 7, 2012 at 10:09 pm #1836103
@b-g-2-2Locale: Silicon Valley
I just had an idea.
One of the routine problems is if you have a butane burner with a wide flame pattern, but your cook pot is very narrow. So, you have too much heat lost up the sides. One thing I made was a tiny strip of titanium foil, and it sits in a circle on the three pot support arms of my burner. That limits the flame, and I use that with my narrow cook pot. As you might guess, the titanium foil gets red-hot. That's OK, because titanium can handle the high temperature.
But, there is still lost heat. If I could get this wire heat conductor top end within or very near that foil circle, it could absorb a lot of heat. In fact, I hope it doesn't melt. If that heat got carried down to the canister, it might make a bigger difference.
–B.G.–Feb 7, 2012 at 11:29 pm #1836117
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