experimenting with cook pots

[Purple]

I started experimenting with different sizes and styles of pots over a Penny Stove and a 1 lb size Coffee Can Wood Stove. One thing I have discovered, that I have not read about, is that a shallow/wide pot boils water 1-2 min. faster than a deep/narrow pot.

I noticed that under shallow/wide pots (mess kit size 7"w x 2" to 3" deep - holds up to 3c.) the fire spreads under the pot but does not extend beyond the edge, so that all the heat is directly under the pot. On the deep/narrow pots (beer can and grease pot types more than 4" deep and 4" or less wide - holds up to 5c) the fire flares out the bottom and heat dissipates in the air, even with a screen. I tested each with 3c water.

I know the less space the "kitchen" takes the better but isn't it better to more "efficient" so you don't have to carry more fuel weight. I will be using the wood burner as much as possible but will use the alcohol when dry wood is not available.

So the question is "efficiency" or "packing size"?

[take-a-knee]

If you get your windscreen about 1/4in away from the pot that will help a little on the taller pot.

[Skidsteer]

It's a compromise for sure.

The real trick is making a stove with a small , yet hot flame pattern for the Heineken pot. It can be done.

[hammock engineer]

Interesting find. It makes sense when you think about it. A larger surface area for the flame to hit.

I'm also in the process of switching pots to some sort of can stove. I have tons of extra room in the pack, so space is not a concern.

Look into putting a bail on the pot. I cook with my pot hanging on it over a fire. Works great if you like having a fire anyways. It makes a good handle too.

[Mr HaHa]

Seems to me you can have both. If you find a wide pot works well with your stove great. And being large does not necessarily make the pot inefficient as far as packability goes. The extra items you can store in it would just have to go somewhere else in your pack anyway.

[Purple]

I'll post pictures of what I came up with (later) and maybe you some of you can give me some more ideas ... Thanks

[take-a-knee]

SGT Rock being the dedicated stovie that he is, changed over to an Evernew pot awhile back, this is probably why.

[Terry7]

Last year I had 2 pots both the same except one was half the height of the other. With the same amount of water in both of them, the short one would boil faster. I used a lid on both, I think because you have less air to heat, you get a faster boil. ???

[No Belay]

I use a titanium MSR kettle. It's squat and wide with a fairly tight fitting lid. I can boil a cup and 1/2 of H2O with only 1/2 ounce of Heet and still have enough flame left get a Liptons back to near boiling. The same procedure took a full oz of fuel when I used an Evernew Titanium pot.

[take-a-knee]

I use a titanium MSR kettle. It's squat and wide with a fairly tight fitting lid. I can boil a cup and 1/2 of H2O with only 1/2 ounce of Heet and still have enough flame left get a Liptons back to near boiling. The same procedure took a full oz of fuel when I used an Evernew Titanium pot.

Was the evernew a larger pot? If so maybe it was a heat sink of sorts.

[highway]

I started experimenting with different sizes and styles of pots over a Penny Stove and a 1 lb size Coffee Can Wood Stove. One thing I have discovered, that I have not read about, is that a shallow/wide pot boils water 1-2 min. faster than a deep/narrow pot.

I noticed that under shallow/wide pots (mess kit size 7"w x 2" to 3" deep - holds up to 3c.) the fire spreads under the pot but does not extend beyond the edge, so that all the heat is directly under the pot. On the deep/narrow pots (beer can and grease pot types more than 4" deep and 4" or less wide - holds up to 5c) the fire flares out the bottom and heat dissipates in the air, even with a screen. I tested each with 3c water.

I know the less space the "kitchen" takes the better but isn't it better to more "efficient" so you don't have to carry more fuel weight. I will be using the wood burner as much as possible but will use the alcohol when dry wood is not available.

So the question is "efficiency" or "packing size"?

Astute observation & I agree. Flames that lick up the sides of the pot loose some of their heat energy into the air surrounding the pot.

[GGS2]

Last year I had 2 pots both the same except one was half the height of the other. With the same amount of water in both of them, the short one would boil faster. I used a lid on both, I think because you have less air to heat, you get a faster boil. ???

Not quite. The lid is to re-condense and save water evaporated from the heating pot. That traps some of the heat which evaporated the water in the first place, which lets the whole pot boil faster.

The other part of the question, wide vs tall, depends on which grabs most heat from the flame and exhaust gas stream from the stove. The heat in the fuel first heats the gases of combustion, the nitrogen and the burnt fuel gases. These gases must then transfer their heat to the pot. There is also some radiative transfer, but most heat is transfered by convection, which means direct contact of hot gas with the pot surface. When the gas stream turns the corner on the pot, it tends to separate from the pot surface, so most of the transfer takes place on the pot bottom. What radiative transfer occurs also must strike the pot bottom, so a large enough pot bottom is the first requirement.

There is a counter argument, which is that heat is lost through the top, and to some degree also the sides of the pot. However, as the flame gases are much hotter than the pot, which hasn't yet boiled, The heat transfer is much faster through the bottom than through the top, and is closer to neutral on the sides, as the hot gases are passing close by there. So the net effect is to be more efficient with a wide pot than with a narrow one.

The Kelly Kettle geometry is different, as in this case heat is transferred not only through the bottom, but also all the way up the chimney, which is conical and which forces the hot gas to remain in contact all the way up. This makes a very efficient heat transfer scheme, which is bought at the price of an awkward interior shape. The KK is really only practical as a water boiler. The prototype of this design is apparently a tea kettle from the interior of China, which is arid and where fuel is scarce. A boiler which uses very little fuel was of great advantage to the nomads there.

In an ideal case, the exhaust gas stream would leave the system at the temperature of the water, there would be no radiative losses (surrounded by a perfect reflector) and no losses from the top (perfect insulator). This is what drives the reflector/wind screen around the pot and beneath the stove, the pot geometry and the lid. With cannister stoves, the ground reflector must be above the fuel cannister for safety reasons.

In any practical case, there will be trade-offs. For instance, if the gap between the pot and the wind screen/reflector is small, more of the hot gas will be in contact with the pot sides, which will increase the heat transfer there. However, the reflector/wind screen will also get hot, so it will lose some heat as well. This will also slow down the gas stream, increasing the dwell time, which is good provided it doesn't stall the burner. So there are lots of small tweaks that can improve the performance of the system. The system is the pot, stove and reflector as a group. Change anything, and it will affect the whole.

A small flame/stove will transfer heat more efficiently, but it will leave a smaller differential between the heat gain vs. heat loss rates. So a large stove is not necessarily more efficient than a small one, up to a point. There is an optimal size of stove for any given system.

There. Now go play. Endless hours of innocent amusement.

[Purple]

I've upload the pics of my Windscreen Stove and my Multi-fuel Stove. The Windscreen stove is original. the multifuel stove is re-designed from another stove I saw somewhere. i need to him credit but I can't remember where I saw it. Your welcome to check them out and ask any question about them - just click on "view my gallery"

[Tinker]

I read something online about 6 years ago regarding pot diameter and boiling times.
Wider pots do work better, especially with lower btu stoves (alcohol stoves).
That's the only reason I'm still using a rather large 1.3 liter Evernew pot rather than something smaller.

[taildragger]

The larger surface area of metal that the water is exposed to allows for better heat transfer, generally speaking.