Stove Test Results - Need help with Math

[layton]

I tested the Soto stove with a titanium pot which is supposedly the best lightweight canister stove (it has a regulator to conserve fuel and help with cold weather operation), the MSR Reactor, and the JetBoil.

 

I timed how long it took to boil one liter of water on each stove, and timed how long it took to run out of 100g of fuel. I then divided the two times to get how many liters of water the stoves could boil with 100g of fuel (the small canisters).

 

 

 

The flaw in my test is that the stoves may perform differently depending on how much fuel is left and how long they were running for. The best way to do it would be to individually boil each liter of water, turning the stove on and off (letting if cool) each time. Also, I had each stove on full blast. The reactor seems like it doesn’t waste fuel based on how high you turn it up, but the other stoves may. They could be at a disadvantage in this experiment due to this fact.

 

 

 

Here are my results:

 

 

 

Observation:

 

The Reactor seemed like it burned the hottest and the most consistently for the life of the cartridge. The flame seems way more evenly distributed than the pinpoint heat of both the Soto and the JetBoil. Also, the pot is wider so it get more surface area heated. It clearly wins the contest as the quickest boiler.

 

The Jet Boil surprised me by being only 4oz lighter than the reactor and taking much longer than expected to boil a liter of water. Since it is thin and tall, boiling less water more frequently may conserve more fuel. However, it would not die. The burn time was incredibly longer.

 

The Soto packs a little punch, but it died out the quickest. I was really hoping it would outperform in cook time, but it didn’t.

 

 

 

Data: (weights are of a 600g scientific scale, boil time is time it takes for the 1st large bubble to hit the surface on 1 liter of water at 32degreesF, burn time is until the flame went out on a 100g canister).

 

Reactor

 

Weight=17.2oz(stove,pot,lid)

 

Boil Time=160sec

 

Burn Time=2920sec

 

Liters boiled/100g=18.25L

 

Jetboil

 

Weight=13.3 (stove,pot,lid,cozy)

 

Boil Time=263sec

 

Burn Time=5360sec

 

Liters boiled/100g=20.4L

 

Soto

 

Weight=6.24oz (stove, titanium pot, lid)

 

Boil Time=270sec

 

Burn Time=2520sec

 

Liters boiled/100g=9.5L

 

 

 

4oz (110g) MSR isopro bottle=6.5oz*

 

8oz MSR isopro bottle=12.5oz*

 

*weights taken from the internet, not confirmed.

 

 

 

Conclusion:

 

It would be nice for someone to help me figure out the break even point where it would make sense to bring the heavier more fuel efficient stove. I’m not very good at this type of math – I’m sure I could figure it out, but I’d question my numbers. Other numbers to figure in are the different weights of a 4oz vs 8oz fuel bottle since it is slightly lighter (but not much) to bring an 8oz bottle.

 

 

 

The JetBoil wins in the most efficient stove, boiling 20.4 L assuming the heat output is the same throughout the test. The Reactor was close behind by about 2 liters less. However, based on pure observation, I’m thinking the Reactor may actually win since it burned consistently hot and boiled water so damn quick. It wins the user friendly test by it’s absurdly fast cook time, and it’s higher volume capacity. I wish MSR would make a limited edition titanium reactor stove!

 

The Soto stove (and perhaps any lightweight stove) wins if you are not going to use up a fuel canister. It could actually win the efficiency test for a couple fuel canisters worth just because of how light the system is.

 

It would be awesome if some mathy-type person could help me figure this out!

 

 

 

I will published the results on my website and hopefully put them in a 2nd edition of my book.

 

[MarkMcJizzy]

It would be awesome if some mathy-type person could help me figure this out!

 

It's probable that Btu output is a variable to each stove, based on the amount of fuel used/remaining. It is likely that your data is so meager to be of no use.

[NoahT]

Since you seem to have the energy for it:

 

To get an idea of performance as the canister gets lower, what if you found 5-6 pots, and as soon as one liter boiled, you pulled it off and threw the next one on. If you timed all the pots, you'd get an idea of how much weaker the performance was at the end of the bottle.

 

Granted your gonna boil like 20 liters of water, so it might get old.

 

N

[dennyt]

I agree with Noah, you should boil pot after pot until the canister dies. The Reactor is supposed to have a regulator, so it should perform close to your prediction. The Jet Boil doesn't, so its performance should go down as the canister empties & the pressure goes down.

 

For interpreting the data, I would use a spreadsheet & make a graph. The horizontal axis would be liters of water to boil, the vertical axis would be total weight. Each stove starts out as [stove + pot + first fuel canister], then stays there until you get to however many liters it will boil with one canister. Then it bumps up by one canister. You should get different stair-step curves for each stove.

 

Melting snow is the more useful, but harder to control, experiment.

 

Because canister temperature affects performance, try to do the tests in a controlled environment.

 

Thanks for doing this! I love testing.

[MarkMcJizzy]

 

Because canister temperature affects performance, try to do the tests in a controlled environment.

 

Try? The testing is meaningless unless it is done in a controlled environmeny

[Dane]

Try? The testing is meaningless unless it is done in a controlled environment

 

Yes...I agree.

And the difference in how the fuel pressure changes in the cans is going to be dramatic. You also would be better served by using the same size cans which you can with all these stoves. Easy to see the obvious winner. Add cold weather to the mix and it is even more dramatic.

 

Always good to have data points though, good work Mike

[dennyt]

 

Send me a PM with your address and I'll email you the spreadsheet.

 

Testing with the canisters in an ice water bath would be a fun variation, too.

[layton]

awesome responses - as for the testing - I'm done. Since there are soooo many variable and different testing conditions, I figured my data is enough to get a rough estimate of each type of stove's worth in different situations.

 

I agree that the best test would be to constantly boil water. I have to return the soto and the jetboil to REI, so if someone else wants to do this on a rainy saturday, I'd love to see the results.

 

Looks like a small stove like the Soto wins on one 8oz fuel canister, but loses to the jetboil after that. The reactor loses in this study, but my unscientific sneaking suspicion is that it would win the water boiling contest. That said, I'd stay with the reactor on trips >4 days unless I already owned the jetboil, but even if I owned the jetboil, I'd still use the reactor in winter.

 

 

Edited June 11, 2010 by layton

[Jim]

A couple points for consideration. I don't like the jet boil as it stands high and more in the wind, a bit shaky. At altitude or in cold you can't tip the canister over to help the flow, also doesn't have a warming tube as some stoves that help in cold weather. Other item - aluminum pots transfer heat much better than titanium so if more than a couple days likely better to go aluminum. I like the MSR windpro for reasons stated above.

[layton]

dane, I used a full 100g of the same brand cartridge on each stove

 

and that graph would look sweet with the weight on the x-axis

[111]

aluminum pots transfer heat much better than titanium

 

Any idea how much better for a similar sized pot? I guess I could just run a test like Mike...

[111]

answered it myself

From Backpackinglight.com:

 

backpackinglight http://www.backpackinglight.com/cgi-bin/backpackinglight/forums/thread_display.html?forum_thread_id=13180

 

""That is only true if the thickness of the two pots is the same. Usually, however, Ti pots are thinner so the difference is minimised or reversed. With the extra thin walls of the Tibetan/FireLight pots your water will boil faster than in most aluminium pots."

 

Hummm.....well....probably not. The coefficient of thermal conductivity for titanium is 21.9W/m per degree C.....and aluminum is 237W/meter per degree Centigrade. Soooo....assuming a similar surface area and temperature differential, Fourier's Law shows the aluminum pot would need to be about 11 times thicker to have the same resistance as the titanium pot.....and I suspect that "most aluminum pots" are not 11 times thicker. Could be wrong.....but I doubt it. (assume Roger will check my math! In general, I think it is safe to assume that aluminum will transmit the stove's heat to your water better.

 

[Dane]

gotcha, thanks. Now if we can only talk you into doing just one more test but with the fuel cans packed in dry ice.

 

Pretty sure that is the same exact temp last time I had to light my stove

[MarkMcJizzy]

 

Hummm.....well....probably not. The coefficient of thermal conductivity for titanium is 21.9W/m per degree C.....and aluminum is 237W/meter per degree Centigrade. Soooo....assuming a similar surface area and temperature differential, Fourier's Law shows the aluminum pot would need to be about 11 times thicker to have the same resistance as the titanium pot.....and I suspect that "most aluminum pots" are not 11 times thicker. Could be wrong.....but I doubt it. (assume Roger will check my math! In general, I think it is safe to assume that aluminum will transmit the stove's heat to your water better.

 

The difference in specific gravity of Al vs Ti is 2.7 versus 4.506. So when density in factored in, a aluminum pot has to be 17.96 times thicker than a titanium pot.

 

But these figures are theoretical. There are many other factors in real life which would play an important role in stove performance.

[layton]

oh, i forgot to add!

the test on the soto stove was done with a GSI brand aluminum pot, not with titanium (as I listed in the weight).

 

 

The reason I swapped the pots out in the numbers was to give the soto stove optimum conditions to see if it had any change of performing near, or outperforming the jetboil or reactor. If it did (and it didn't) then I would have re-ran the test with an aluminum pot.

[JoshK]

Mike, you mentioned in winter you'd take the Reactor over the Jetboil, despite the relatively similar efficiency. Is your preference for the Reactor because of the faster boil team and larger pot? I have a Jetboil I was given as a gift, and overall I find it pretty decent, but that small pot sure does make snow melting a marathon affair.

[ivan]

what about cooking w/ c4?

[tradhead]

Mark - Pretty sure that steady-state heat transfer is not a function of specific gravity of the materials under evaluation.

 

Checking Matweb the 11X ratio on thermal conductivity seems reasonable. (Not sure about the delta T associated with the thermal condctivity values from Matweb but will verify the trend at work tomorrow.)

 

 

[Maxtrax]

Josh, from my own experience I favor the Reactor over the Jetboil for almost any trip for three key reasons - faster boil times, way better/more consistent performance in the wind (i.e. brew stops) and a large enough pot to actually be useful for 2 people or melting snow.

 

I rarely take either during the summer, typically opting for cold food or my Brunton Crux which with a lightweight Al pot is a smaller package and is lighter overall for trips up to about 9 or 10 days.

 

Edit to add:

One stove I'd still really like to mess around with but never have is the MSR WindPro. I'd be curious to see if combined with a lightweight Al pot and a good titanium windscreen it could give the Reactor a run for its money melting snow by keeping the remote canister warmer and/or inverted to burn off the butane faster as it liquefies in the cold.

 

Another interesting test would be to compare different brands of canister fuels/mixtures of isobutane and propane to see which (if any) performed better in colder weather or as the canister is diminished.

Edited June 11, 2010 by Maxtrax

[tvashtarkatena]

 

Hummm.....well....probably not. The coefficient of thermal conductivity for titanium is 21.9W/m per degree C.....and aluminum is 237W/meter per degree Centigrade. Soooo....assuming a similar surface area and temperature differential, Fourier's Law shows the aluminum pot would need to be about 11 times thicker to have the same resistance as the titanium pot.....and I suspect that "most aluminum pots" are not 11 times thicker. Could be wrong.....but I doubt it. (assume Roger will check my math! In general, I think it is safe to assume that aluminum will transmit the stove's heat to your water better.

 

The difference in specific gravity of Al vs Ti is 2.7 versus 4.506. So when density in factored in, a aluminum pot has to be 17.96 times thicker than a titanium pot.

 

But these figures are theoretical. There are many other factors in real life which would play an important role in stove performance.

 

Specific gravity has absolutely nothing to do with calculating heat transfer.

 

Pots are not just flat plates; they're essentially pipes that are capped at the bottom. To compare the efficiency of heating a set volume of water, you've got to take into consideration the heat transfer into the water a) through the base, b) from the base through vertical walls of the pot both, as well as the c) heat lost to the air through the walls and lid of the pot.

 

© is critical. Pot material or wall thickness is probably negligible as compared to flame geometry and pot geometry, both for boiling water quickly and efficiently (two completely different criteria).

 

To say Layton's real world tests are worthless reveals a lack of understanding of the overall problem. A couple of degrees difference in air temperature is negligible, considering that the conductivity of water is 240 times that of air, and that of any metal is thousands of times greater. Heat lost to the air due to big flame/small diameter pot is not going to be substantially effected by such minor changes either.

 

Air is 240 times less conductive than water, so any heat pumped into the metal is going into the water, not the air.

 

Any heat not transfered directly through the bottom of the pot and into the water is either a) lost to the air b) conducted from the air into the water through the walls of the pot or c) conducted directly through the walls of the pot into the water. Since air is 240 times less conductive than water, most of the heat transfered to the walls of the pot will go into the water. What actually happens depends on flame versus pot geometry. If the flame envelopes the walls of the pot, a thinner pots is probably better. If not, a thicker walled pot, which transfers more heat into pot's walls and into the water (rather than surrounding air),might actually heat water more efficiently. A thicker pot will

 

BTW,

[shapp]

Is the weight that significant of a differnence, your weight varies more than that depending on weather you just took a crap or not.

[catbirdseat]

I agree that the best test would be to constantly boil water. I have to return the soto and the jetboil to REI, so if someone else wants to do this on a rainy saturday, I'd love to see the results.

 

If one were interested in testing the efficiency of the stove as one heats liter after liter of water, the results would vary depending on whether the canister were allowed to warm back to room temperature after each liter was boiled. This is the usual way that stoves are used.

[Wastral]

The ultimate pot, would be copper plated aluminum on the bottom with Titanium outter wall and an aluminum inner wall and a Titanium lid. I would have to wonder how much a pot like that would cost though...

 

I have both Aluminum pots and TI pots. The aluminum pots are also lighter, but burn through if used as ovens. If I am boiling water I always use the AL pot as it boils the water much faster. One MUST always have a very good wind screen. Convection via the wind is a big problem in an alpine environment. If I am going overnight I take the TI as they have the no stick coating. BUT if I am melting snow, DO NOT TAKE pans with a NO - STICK coating!@#$%^ You will quickly have a pans with partial "no-stick" coating making any food you cook in said pan later taste horrible and eating all that silicon. Yum... YUCK!

 

PS If you are melting snow make sure to dump some water in the bottom to help conduct the heat better from the bottom of the pot into the snow/ice. This will cut a full minute or so off of your boiling time on a typical 2 quart pot.

[Moof]

Why not just get a decent scale? Weigh the fuel before and after.