Fast heating times vs fuel efficiency

11:58 p.m. on February 18, 2011 (EST)
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When reading backpacking stove adds I often read the words fast and efficient as meaning the same thing. As mentioned in my introduction I have setup some stove testing equipment in my garage at home. I wanted to know if faster was more efficient or is it just more of the marketing spin that we are so used to.

Below are the results of some test that I did some time ago where I compared Alcohol, Petrol (White gas or Shellite) and Gas (Canister) stoves vs time to boil and to each other.

I tested a Trangia 27-1, a MSR Whistperlite and MSR Pocket Rocket all of them are considered to be classic stoves and are available in most countries of the world.

The tests where done through a range of adjustment settings from the fastest to the slowest that I could get the stoves to operate with in reason. I used a 1l Snowpeak Titanium pot 150 mm diameter with a specially made Stainless Steel lid with a hole in the middle so I could place my temperature measurement probe into the water, I used 1 liter of tap water in these tests.

All test results have been normalised, I measure the start temp of the water and stop the tests when the water reaches 95C, I weigh the fuel at start and at end, I then calculate the fuels used per 1C temp rise I then normalise to fuel used per 80C, the ambient temperature for these test was around 20C.

Adjustment

With the Trangia I used the simmering ring to choke the flame down to produce the slower heating rates, the fastest heating rate used was with no simmer ring.

The Whisperlite was the hardest to adjust, I did this by pumping different number of pumps into the fuel tank from a few pumps at a time to about 40 pumps and the valve was opened fully in all tests.

With the Pocket Rocket, this was simple I adjusted the heating rate by adjusting the valve from very fast to very slow, if the valve was opened too much lift off of the flame was experienced

Results

The results show the amount of fuel used in each test in grams vs time.


PetvsAlcvsgas.jpg

Trangia

Note that no matter how slow I adjusted the heating rate it used the same amount of fuel from 12 minutes to 30 minutes. 23-24 grams, Note the Trangia used nearly twice as much fuel as the correctly adjusted Pocket Rocket, this roughly is in line with heating energy contained in the different fuels.

Whisperlite

The Whisperlite showed great improvement in efficiency 25% with slowing down the heating rate, this stove is not design to simmer and is very inefficient at the normal setting, though it has the advantage of working in very cold conditions.

Pocket Rocket

The Pocket Rocket also benefited from slowing down the heating rate a 25% improvement was seen. Note as can be seen from the curve (yellow line) that using the Pocket Rocket at too high a heating rate is a waste of energy, a time of around 12 minutes seems to be the optimum and heating rate faster was a waste of fuel and slower was a waste of time. Please note the most efficient fuel/time point 12 minutes coincides with the fastest heating rate from the Trangia 12 minutes, I am not sure if this means anything though but I found it an interesting point. Upright canister stoves have problems working in cold conditions but they can still work in the cold if used correctly.

Conclusion

Is fast boiling, efficent boiling, I think my results speak for themselves.

I hope this information is of some help to stove users and prospective stove buyers.

Tony

Please note, I have previously shared this information on some other forums and on my blog.

 

5:11 a.m. on February 19, 2011 (EST)
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This is interesting and helpful, thanks.

Wouldn't it be great if Trailspace had a 'Technology' sub-forum in the Gear Section? ;-)

Cross-posting there might not be a bad idea, though.

8:10 a.m. on February 19, 2011 (EST)
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I don't know if there is good data available evaluating stoves under different variables, such as ambient temperature, cross breezes, elevation, pot size, mass of materials being heated, etc.  Intuition leads me to believe some stoves are better for specific conditions, thus a test at sea level my not reveal performance capabilities at 11K.  Some manufacturers are starting to include performance specs with their products, however, the aforementioned issues and the fact these specs are not certified lead me to take them with a grain of salt.

Ed

4:42 a.m. on February 20, 2011 (EST)
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This is interesting and helpful, thanks.

Wouldn't it be great if Trailspace had a 'Technology' sub-forum in the Gear Section? ;-)

Cross-posting there might not be a bad idea, though.

 Hi Pathloser,

A Technology section would be good but I am to new to this forum to have any infulence.

Tony

4:58 a.m. on February 20, 2011 (EST)
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I don't know if there is good data available evaluating stoves under different variables, such as ambient temperature, cross breezes, elevation, pot size, mass of materials being heated, etc.  Intuition leads me to believe some stoves are better for specific conditions, thus a test at sea level my not reveal performance capabilities at 11K.  Some manufacturers are starting to include performance specs with their products, however, the aforementioned issues and the fact these specs are not certified lead me to take them with a grain of salt.

Ed

 Hi Ed,

You have raised some very good points, testing stoves at sea level at 20C is not representative of real world field use. I would love to be able to test stoves at much colder temperatures, 0C, -20C and colder. I have looked into building a cold temp test facility, but for me this is prohibitively expensive to do, as I do stove testing for a hobby, all costs come out of my own pocket.

I would imagine some of the bigger stove manufacturers do cold temperature stove testing, they would be keeping results under wraps.

Tony

 

 

 

8:48 a.m. on February 20, 2011 (EST)
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..I would imagine some of the bigger stove manufacturers do cold temperature stove testing, they would be keeping results under wraps...

I am sure they test their products, but they also take feed back from field testing.  I am inclined to believe the process starts with making something that works in the lab, then gets someone to take their product up the hill and see how it works under real world scenarios.  Since field tests are as much about human factors as technical issues, it would not be surprising to discover the most efficient stoves don't always make the cut.  I too dabbled, attempting to lighten stove and lantern weight, and improve fuel efficiency.  Ironically all of the designs that were the lightest and most efficient also were un-safe and/or difficult to operate. 

Despite over a century of innovation, there are many who still swear by their generations old Optimus WG fuel stoves, several models whose benchmarks are still very respectable.   My favorite stove of all time is the MSR WG fuel firefly.  The firefly came out after the XKG.  It burned almost as hot as the XKG, but had a better pot stand and was lighter.  Like the XKG the flame control was good; the flame could range from a candle to a roar (the only short coming was it literally roared).  For reasons unbeknownst to me MSR took the firefly off the market less than five years after introducing it. 

Ed

12:41 p.m. on February 20, 2011 (EST)
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Tony,

Always good to get another person testing stoves. Jim S, who posts on Trailspace from time to time, and I have done a lot of tests over the years on ways to improve stove efficiency and heating times in a range of temperatures, ranging from a standard (stove, water amount and temperature, air temperature at STP - standard temperature and pressure as the chemists define it - what do you expect? Jim is an engineer and I am a scientist) to real world cold, altitude, and wind conditions. There are a number of ways to improve efficiency of heat transfer, which generally (but not always) improve fuel efficiency. Some examples you might play with - blackened pots (think header paint or carbon deposits like alcohol stoves leave), wind screens (but be careful not to set things up to direct heat onto the fuel container, especially for compressed gas stoves), heat exchangers, heat directors, cook pot materials, cook pot design, lid on vs lid off, and many more.

You used a titanium pot. Keep in mind that titanium is used in high speed aircraft because Ti is a poor conductor of heat. Among readily available pots for backpacking, aluminum (particularly black anodized aluminum) is the best conductor and spreads the heat most evenly. Cast iron works well, too, but is heavy for backpacking, and usually too heavy for most backpacking stoves. Some alloys of iron work fairly well (think the typical iron woks used in oriental cooking, though GSI makes two anodized aluminum woks that do as well as our iron wok), though they tend to rust unless you take diligent care of them. Stainless steel is significantly less of a heat conductor than cast iron, though much easier to maintain. Aluminum and copper clad pots are not as good as straight aluminum, but much harder to maintain in the field.

Your mention of the Trangia brings up a point that most people are unaware of with respect to alcohol stoves. Trangia (and other alcohol stove makers) makes a range of stoves, the most basic of which is just a burner with some arms to hold a pot and the most sophisticated of which includes a very efficient windshield/heat director. "Boil times" differ by a huge amount between the two extremes in the Trangia line, with the more sophisticated design being into the range of compressed gas and liquid fuel stoves, due to the improvement in heat transfer efficiency of the windshield/heat director design. My wife recently obtained an Esbit stove that has a similar design, and Sigg used to make a similar design of alcohol stove (plus an alcohol stove that had a burner that was reminiscent of an up-draft carburettor, hence was very fast to boil).

Speaking of burner design, the burner design can make a significant difference. The "roarer" burner (the type used on the venerable Svea 123 and the MSR XGK) is more efficient in many respects than the "silent" burner used on most compressed gas stoves and the Whisperlite. There is not a lot of difference in the two styles of "silent" burner, though (the screen style used on most compressed gas stoves, such as the JetBoil and Pocket Rocket, as well as the liquid fuel MSR Simmerlite; and the "waffle plate" style used on the MSR Whisperlite and the Coleman Peak 1 International). The "silent" burner (which isn't really all that silent) has one big disadvantage over the "roarer", though. When you get it wet (trying to cook in the rain, dumping it accidentally into the snow, or spilling your soup by boiling it over), the "silent" burner is a pain to get cleaned up and restarted. The advantage of the "waffle plate" style is that you can take the burner apart into the individual plates and clean it (good idea to do this periodically to clean carbon deposits anyway), something you can't do with the "screen" type burner. The "roarer" burner can just be wiped dry and maybe clear the jet.

Keep up the testing, and continue to post your testing procedures. It is important to know that. There was an infamous case of a wide-circulation outdoor/climbing magazine that did a series of tests on stoves about 8 or 9 years ago and came up with results that were strangely anomalous - one stove that could use either liquid fuel or compressed gas was tested for both, with the boil time for the liquid fuel being in the 3 minute range and the compressed gas being in the 7 minute range (over twice as long). I happened to have that same stove and found that on either fuel, the boil times were in the low 3 minute range, with the compressed gas being slightly faster, if anything. I later had a discussion with the magazine's tester and got only the reply that "the results were the results", no explanation of how the tests were done.

5:01 p.m. on February 20, 2011 (EST)
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Testing stoves and using stoves are certainly two different things aren't they?

I have tested stoves at home using controlled tests and found that those results don't always correlate with my end results while using them in the backcountry under poor conditions.

A lot of factors to consider, wind screen function, effects of cold on the fuel, ease of setup in difficult situations, etc.

In the end I am happiest when I can eat well with the least amount of trouble. Weight, boil time, & fuel consumption aren't always my biggest concerns when I'm cold and hungry. Ease of operation and reliability has a lot of value as well.

5:56 p.m. on February 20, 2011 (EST)
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Hi Bill,

Many thanks for your very detailed reply, it is certainly nice to make contact with other stove testers.

First some of my back ground, I have just clocked up 40 years in the workforce mainly as a machinist, I have an Advanced diploma in Mechanical Engineering and some basic electronics too. I work as a senior technician in a University research lab (24 years), we do research into Geophysical Fluid Dynamics (Ocean/Atmosphere Dynamics and Lava dynamics). Besides expertise in machining metals, plastics, design and manufacture of scientific equipment, I have expertise in temperature, density, viscosity measurement and fluid visualization techniques. I would like to retire in the next two years but it will be difficult, as I love my work.

Testing stoves in the full range of real world conditions is always going to be difficult or very expensive to replicate in a lab situation, comparing stoves/ pots etc under the same conditions, ambient temp, windless or with fan, is the best I can do with the resources I have.

For those that are interested I will post a full technical report of my testing gear very soon.

With stove/pot testing I am currently involved in a project with a retired scientist and technology editor for an on-line magazine, we are testing most of the conditions that you have mentioned, different pot materials (Al, Ti SS, HA Al), black pots vs shinny pots, pot size vs stove flame size (at the moment I have only done tests with alcohol stoves, canister or compressed gas stove tests are to come) I am unable to publish results here as the results will be published in the on-line mag.  What I can tell you that even though Ti has much lower thermal conductivity compared to Al, when boiling water I see very little difference with performance, I have many Ti pots and after many years of field use of Ti, Al and Al flux ring pots I now prefer and use some cheap Al billy pots in all seasons (more on that later).

I have done many tests on flux ring pots both in the lab and field and have come to the conclusion that unless you want a fast boil, flux ringed post are not worth the extra weight.

The Trangia is a very good stove but heavy, I have tested many alcohol stove designs and the Trangia up there with the best with efficiency, I have not tested the Trangia canister gas or white gas conversions, my budget does not allow me to purchase every stove on the market.

My only experience with White gas stoves is with the MSR Whisperlite, this was my second stove after the disasters of trying to cook with my Trangia 27-1 in some very cold conditions, my Whisperlite was a good stove but failed on me one snow trip, trying to clean the jet out when dark and very cold was not fun, I also did not like that it was very hard to simmer with it. I have had one experience with the Dragonfly, we had arrived at a hut on the Overland Track in Tasmania and the hut was occupied by a family who where cooking lunch with a Dragonfly, I had heard they are nicknamed conversation busters and I now know why. I am looking forward to the release of the new Soto OD-1NP Muka stove, which does not require priming.

My current winter stove is a Coleman Extreme remote canister stove, sadly these are no longer made, with some they are the gold standard cold weather pressurized gas stove.

I use a Kovea Supalite stove in the warmer months when cooking for two, when I walk with my club and cook for myself I use my little MYOG 17g remote canister stove that I made.

I get very annoyed when I read claims like “Boils 1 liter of water in under 3.5 minutes.” (this is from the MSR Pocket Rocket site) I have tested the Pocket Rocket so much that I wore out the needle valve, and I have never been able to replicate those boil times, I suspect they start with very warm water and maybe stop heating when the bubbles appear on the bottom of the pot and the Tri-sectional windclip is marketing BS as far as I am concerned, but do not get me wrong the Pocket Rocket is a good stove, I do own two of them.

Tony

6:08 p.m. on February 20, 2011 (EST)
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Testing stoves and using stoves are certainly two different things aren't they?

I have tested stoves at home using controlled tests and found that those results don't always correlate with my end results while using them in the backcountry under poor conditions.

A lot of factors to consider, wind screen function, effects of cold on the fuel, ease of setup in difficult situations, etc.

In the end I am happiest when I can eat well with the least amount of trouble. Weight, boil time, & fuel consumption aren't always my biggest concerns when I'm cold and hungry. Ease of operation and reliability has a lot of value as well.

Hi trouthunter,

I understand what you are saying.

I have made several canister gas stove, after the initial tuning they all worked very well and reliably on the test bench, the first time in the field most have failed, usually leaky fittings, when testing an untried stove I always carry a second stove.

Tony

 

7:25 p.m. on February 20, 2011 (EST)
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Testing stoves and using stoves are certainly two different things aren't they?

I have tested stoves at home using controlled tests and found that those results don't always correlate with my end results while using them in the backcountry under poor conditions.

A lot of factors to consider, wind screen function, effects of cold on the fuel, ease of setup in difficult situations, etc.

In the end I am happiest when I can eat well with the least amount of trouble. Weight, boil time, & fuel consumption aren't always my biggest concerns when I'm cold and hungry. Ease of operation and reliability has a lot of value as well.

Hi trouthunter,

I understand what you are saying.

I have made several canister gas stove, after the initial tuning they all worked very well and reliably on the test bench, the first time in the field most have failed, usually leaky fittings, when testing an untried stove I always carry a second stove.

Tony

 

I don't think it would be safe for me to build canister stoves, so I'll leave that to you, but I would like to know more about yours.

I have made a few alcohol stoves and a couple wood gas stoves and they all took more than one try, that's for sure.

12:21 p.m. on February 21, 2011 (EST)
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 What I can tell you that even though Ti has much lower thermal conductivity compared to Al, when boiling water I see very little difference with performance, I have many Ti pots and after many years of field use of Ti, Al and Al flux ring pots I now prefer and use some cheap Al billy pots in all seasons (more on that later).

I have done many tests on flux ring pots both in the lab and field and have come to the conclusion that unless you want a fast boil, flux ringed post are not worth the extra weight.

.....I have had one experience with the Dragonfly, we had arrived at a hut on the Overland Track in Tasmania and the hut was occupied by a family who where cooking lunch with a Dragonfly, I had heard they are nicknamed conversation busters and I now know why.

.....I get very annoyed when I read claims like “Boils 1 liter of water in under 3.5 minutes.” (this is from the MSR Pocket Rocket site) I have tested the Pocket Rocket so much that I wore out the needle valve, and I have never been able to replicate those boil times, I suspect they start with very warm water and maybe stop heating when the bubbles appear on the bottom of the pot

Couple of comments:

Ti pots generally are very thin, which does two things as far as heating and cooking are concerned. First, being that thin means that the heat can get through to the water faster, which partly makes up for the lower conductivity. Second, in practical terms for cooking, all the heat is transfered through a small area on the bottom of the pot. Two consequences - a heat exchanger doesn't help very much with thin pots generally, especially if they are Ti, so the boil time is not slowed by very much; and when you want to cook something that requires simmering (so you want the heat to be spread out through the whole pot), it is very easy to burn something at the bottom of the pot in a small circle (been there, done that). Part of the same problem is that when melting snow for water, you MUST have some liquid water at the bottom of the pot, or else you scorch the snow - there is nothing so foul-tasting as scorched water. It is all too easy to start dumping dry snow (that is, low temperature snow, which has no liquid water on the surface of the flakes), and have it act like a sponge, leaving you with a scorched pot bottom.

Something most people do not know about the DragonFly (even though it is, gulp!, actually in the instruction sheet (who reads instruction sheets or manuals), is that you need to follow a particular shutoff procedure and you need to remove and clean the needle valve fairly frequently. The shutoff procedure is, when done cooking, close the pump valve first (the one at the fuel bottle end. Then open the needle valve fully (the one at the burner end of the hose). Let the flame burn down until it just gets a tinge of yellow flame (you are clearing the liquid fuel out of the fuel line). Then blow the flame out and leave the needle valve open to allow the fuel vapors to evaporate and escape. This lengthens the time between needed needle valve cleanings by reducing the amount of "lacquer" buildup in the hose and in the needle valve.

I have typically gotten 3.5 min boil times with the JetBoil. I start with STP - 20C water, 20C air temperature, sea level on a typical spring or fall San Francisco Bay Area day (I live at 2 meters above sea level, so on such a day, the absolute air pressure is very close to 1000 millibars, and midday temperatures in the Spring and Fall are very close to 20C, plus being within 1 km of the SFBay, the temperature is well moderated naturally). The location on my back patio is well-shielded from any winds. so I am as close to a controlled lab setting as you can get without having a full research lab. That does require using a new, full canister of the 250 or 500 gram size (since the pressure drops as the canister is emptied). And I do use full rolling boil as the criterion. The pot is anodized black aluminum and is covered to do this. As you and others have noted, the timing does vary by a lot in the "real world" of half-empty canisters, varying temperatures, varying altitudes, with wind, etc etc.

7:35 p.m. on February 21, 2011 (EST)
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such a great thread, Gentelmen. Very informative for me, in particular regarding Ti pots and scorched snow.

Thank you for sharing your experiences.

5:25 a.m. on February 22, 2011 (EST)
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Hi Bill,

Thanks for your comments, I am enjoying this exchange of knowledge.

The thickness difference from Al to Ti pots does not explain the lack of difference in performance, I have just measures some of my pots and the Al pots that I use in my tests are 0.65mm thick, a JetBoil PCS pot is 1.00 mm thick, my BPL 550 Ti pot is 0.32mm, SnowPeak 1liter pot is 0.48 mm and my MSR Ti pot is 0.45 mm thick, 0.65mm and 0.045 is not that much thickness difference to make up for the difference in thermal conductivity. The Coefficient of Thermal Conductivity of Ti is from 4.8-22.7 W/m.K depending on alloys, pure Ti is supposed to be around 16 W/m.K, I normally use 15.0 W/m.K, Al is 206W/m.K.

One of the main reasons why I use Al pots is that for my evening meal I re-heat food and cook rice and pasta, I found heating/cooking my meals in Ti the food burnt easily, I do not have this happen in my 0.65 mm thick Al pots, and my Al pots are lighter than the equivalent size Ti pots too.

My house is at 600m elevation, I have measured the boiling point of my tap water with some very accurate thermometers at around 98.357C to 98.400C, boiling point can vary a little bit according to atmospheric pressure, that is why I stop my tests at 95C. The most efficient pot that I have tested is the JetBoil GCS pot, my JetBoil stove has something in it that limits the flow rate and it is very difficult to have on too high a setting. I have never been able to have the fast boil times that you and the manufacturers are stating.

Bill wrote>That does require using a new, full canister of the 250 or 500 gram size (since the pressure drops as the canister is emptied).

When a canister is in use in the upright position, the latent heat of evaporation will cause the contents to cool down, this will reduce the internal pressure but if the canister is kept at a constant temperature and while there is liquid gas inside the canister and the gas mixture remains the same the pressure, but if the Propane boils off faster which normally happens, the pressure will drop until all of the propane boils off.

I one uses a liquid feed canister gas stove then there is no problems with loosing canister pressure during use.

Tony

9:22 a.m. on February 22, 2011 (EST)
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..Bill wrote>That does require using a new, full canister of the 250 or 500 gram size (since the pressure drops as the canister is emptied)...

 

Actually the pressure inside a canister isn’t affected by fuel level until almost empty.  Perhaps there are stoves that can consume gas faster than evaporation replaces it, and that could account for Bill’s comment, but I have not encountered such a stove.  (Of course Bill may specifying a full canister to eliminate fuel level from being a dependant variable for whatever reason.) Canister pressure is a function of evaporation and the rate the burner can consume gas.  Assuming the same regulator setting, the fuel will evaporate and replace consumed gas at the same rate in a ¼ full canister as a ¾ full canister.  What affects canister pressure is the temperature of the contents, and the amount of surface area where evaporation takes place.  Tipping your canister at an angle increases the surface area available for evaporation, while managing to somehow warm the canister contents will enhance evaporation performance too.  While continuous use will cool the fuel enough to eventually affect evaporation rate, the typical tests of bringing small volumes of water to a boil do not last long enough to have a significant affect. 

Another factor that comes into play is the consequence of using blended fuels in cold weather.  Butane and propane evaporate at different temperatures – I imagine they also may create different canister pressures, depending on if cold weather use causes one gas to become exhausted before the other.  But then the performance problem is more the result of the chemical properties of each fuel, not canister presure per se.

Ed

1:23 p.m. on February 22, 2011 (EST)
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...Actually the pressure inside a canister isn’t affected by fuel level until almost empty.  Perhaps there are stoves that can consume gas faster than evaporation replaces it,... Canister pressure is a function of evaporation and the rate the burner can consume gas.  ....  While continuous use will cool the fuel enough to eventually affect evaporation rate, the typical tests of bringing small volumes of water to a boil do not last long enough to have a significant affect. 

Another factor that comes into play is the consequence of using blended fuels in cold weather.  Butane and propane evaporate at different temperatures – I imagine they also may create different canister pressures, depending on if cold weather use causes one gas to become exhausted before the other. 

Tony's comment:

When a canister is in use in the upright position, the latent heat of evaporation will cause the contents to cool down, this will reduce the internal pressure but if the canister is kept at a constant temperature and while there is liquid gas inside the canister and the gas mixture remains the same the pressure, but if the Propane boils off faster which normally happens, the pressure will drop until all of the propane boils off.

is the explanation. First thing is that the pressure is provided in vapor-feed stoves by evaporation of the liquid butane/isobutane/propane mix. The remaining liquid and the container are cooled, which slows the evaporation rate. This becomes particularly noticeable when the canister is less than half full. Using the stove in cool weather, as Tony notes, the propane evaporates faster than the butane. When the propane is burned off, you can end up with the remaining butane being cooled to 0C/32F, at which point you get no more vaporization to provide pressure. Tony's point about keeping the canister at a constant temperature is important, but impractical in the "real world" (except for the old trick used by some of us during cold weather of setting the stove in a pan of water, which keeps the canister above freezing - don't use hot water, though!!!). Also, if you use an inverted canister stove, which feeds liquid instead of vapor, the effect is much reduced (JetBoil's Helios, or using the Primus inverted canister stand). Using a full canister for the tests means you have more liquid to distribute the heat loss, hence moderate the cooling. When you get down to half or less full, you have a larger volume to pressurize and smaller mass of liquid to act as the heat source.

On the inverted canister, some of us discovered years ago that with the hose-mounted remote canisters you could use a compressed gas stove in much colder temperatures. I don't recall where I first heard about this (probably from Jim S), but the idea was based on the way the Coleman X-stoves were set up. They had a canister that lay on its side with a hinged pickup tube that would always sit with its pickup opening on the bottom of the canister, hence feeding liquid fuel. When I first tried this with my Primus MFS, I found it worked very well, except the keeping the canister inverted was a pain. I talked to the various stove people at several Outdoor Retailer Shows. Coleman said "absolutely do not do that!", despite the fact that their X-stoves were doing exactly the same thing. Within a year, they had come out with an adapter for one of their remote canister stoves. Primus soon came out with their stand. And several years later, JetBoil came out with the Helios (claiming that they had invented the idea, even though it had been circulating in the climbing community for 4 or 5 years).

Anyway, there have been a number of schemes used to overcome the cold weather problem of canister stoves, some of which work very well (the canister in the pan of water, the inverted canister, the handwarmer in the cavity on the bottom of the canister), and some of which are risky at best.

Disclaimer - just because I mention some technique or way of using some piece of gear does not mean it is safe. DO NOT DO ANYTHING THAT IS NOT ENDORSED BY THE MANUFACTURER OF THE GEAR! People get away with all sorts of dangerous and risky things... for a while, then have an accident that results in injury or death. So only do what the manufacturer approves (that way, the manufacturer is responsible and none of us hackers).

8:23 a.m. on February 25, 2011 (EST)
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Re: Bill’s post, 2/22/2011, 1:23 p.m.

In so many words I attempted to describe what both you and Tony describe, that stove efficiency is affected by how fast the fuel vaporizes, hence its ability to maintain an effective operating pressure.  Obviously as vaporization occurs it causes the remaining liquid to cool, retarding the rate of vaporization.  My point is the typical bench test of bringing one liter of water to a boil doesn’t last long enough to significantly cool the liquid fuel, hence retard the vaporization process that makes gas available for combustion.  I also stated fuel level status (implying volume of fuel equates to ability to act as a heat sink) only becomes significant when the stove is operated for sustained periods; or when ambient starting temperature of both liquid fuel and external air are close to or below the boiling point of the fuel compounds.  Specifically when the liquid fuel chills to approximately 32 F, the butane will no longer vaporize unless a vacuum is applied.  This causes only the propane to vaporize which subsequently gets burned off until exhausted, or until the liquid is chilled to somewhere south of -44 F, in which case evaporation ceases, and the stove sputters and dies. 

My personal experiences bear this out: I have never had a canister stove performance issue related to fuel and the evaporative process that generates gas, while camping in warm climates, regardless of fuel volume status or duration of stove operation.  On the other hand extreme cold external air temperatures can quickly compromise evaporative canister stove performance, regardless of fuel level.  I chock up most poor operation experience to the lower delta value between the ambient temperature of cold external air, and the initial temperature of the tank’s contents, thus reducing the total BTUs the liquid fuel can shed before latent heat chills the liquid down to its boil point.  I also believe performance is affected by the canister’s efficiency as a heat exchange medium between the canister’s contents and the external air.  Thus given the typical four minute boiling time test, the initial temperature of the exterenal air and liquid fuel contents, coupled with the rate fuel is burned, seem to have by far the greatest influence on stove efficiency, and its ability to remain efficient as the duration of the test of the test is extended.  As burn time is extended, however, other factors will gain relevance on stove efficiency (e.g. fuel volume, heat exchange properties of the canister body, etc).

The implications of this opinion point out stove efficiency may be gained several ways. 

1.  Manufacturers could fabricate canisters utilizing materials that are more efficient heat exchange media.

2.  Operating stoves at reduced gas flow rates lowers the minimal ambient air temperature required to efficiently operate your stove for extended periods.  Lower flow rates equate to lower evaporation rates, which equate to less heat exchange demands placed on the canister body, and increased probability the liquid fuel will remain above the fuel compounds’ respective boiling points.

3.  Enlarging the canister volume will permit longer periods of efficient operation in marginal ambient air temperatures, but practicality limits this option.  It would be nice to have a larger canister, about double the size of the conventional large canister currently marketed by most manufacturers, as that is typically about how much fuel my party size consumes during a week long trip.

4.  For the same reasons that substantiate conclusion #3, there is a limit how small a canister can be and still deliver acceptable performance.  At some point there is neither sufficient fuel volume to counter the effect of latent heat, or tank surface area to act as an effective heat exchanger between the tank contents and external air.

5.  There may be more suitable fuels, meaning fuels with lower boil points, yet equal or superior in capacity to generate heat.  How much more is one willing to pay for this gain, if increased cost was the result?

6.  Screw it!  If efficiency really matters so much, get one of the inverted canister stove systems, or a pump stove, you’ll be glad you did it.  I own both canister and white gas fuel stoves.  I prefer the white gas stoves on cold outings, because I have grown tired of sleeping with canisters in my sleeping bag, or warming them under my clothes.  I also am tired of worrying about accidents arising from attempts at keeping the canister warm, utilizing the heat generated while under operation, and other generally unauthorized tricks.  I know the inverted canister stoves should preclude performance issues in all but the coldest situations (conditions I don’t ever intend to visit), but the emotional affect of past experiences with canister stoves in extreme conditions serve to cancel out clear headed logic.  Like Mike, subjective biases affect my judgment regarding what criteria defines a good stove.  Lastly I found the “maintenance free” nature of canister stoves means you can’t affect field repairs if a cooking spill ends up blocking the fuel port, something that is inconvenient in warm weather, but can have dire consequences when relying upon melted snow or ice for water.

PS: Tony I totally understand your apprehension regarding fiddling around with prototype canister stoves.  I had some pretty silly, sometimes scary experiences while trying to design a lightweight white gas lantern back in the late 1980s when the Peak 1 lantern was the lightest thing available.

Ed

9:03 p.m. on February 25, 2011 (EST)
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I haven't taken the time to read every word in this thread but I don't think I see anything about the "heat exchanger" devices produced by MSR (and built into Jetboil?). It seems to me that the rates of heat loss around the pot (might explain why slower is better in your results, Tony),  transfer through the sides of the pot, and loss from the pot to the air are all potentially important, and these devices attempt to limit or recapture these sources. But do they work? Has anybody tested these, especially in cold conditions? Do they really do anything? Are they worth the weight?

Also, speaking of capturing every last bit of heat, I wonder if anyone has revived the "Nansen cooker" for hard core winer conditions (especially with larger groups where it might actually be practical)? This approach has the heat travel between an outer pot used to melt snow and an inner pot used for cooking.

12:47 a.m. on February 26, 2011 (EST)
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I haven't taken the time to read every word in this thread but I don't think I see anything about the "heat exchanger" devices produced by MSR (and built into Jetboil?). It seems to me that the rates of heat loss around the pot (might explain why slower is better in your results, Tony),  transfer through the sides of the pot, and loss from the pot to the air are all potentially important, and these devices attempt to limit or recapture these sources. But do they work? Has anybody tested these, especially in cold conditions? Do they really do anything? Are they worth the weight?

Also, speaking of capturing every last bit of heat, I wonder if anyone has revived the "Nansen cooker" for hard core winer conditions (especially with larger groups where it might actually be practical)? This approach has the heat travel between an outer pot used to melt snow and an inner pot used for cooking.

 

 

First I will reply to Bill and Whomeworry later, I have been busy with another project and time is short at the moment.

Hi BigRed,

Thanks for your Heat exchanger question, a very good question.

I have done a little bit of work into comparing heat exchanger pots to normal pots, I have written a test on a flux ring pot up and posted it on my blog http://tonysbushwalking.wordpress.com/2010/08/22/are-pots-with-flux-rings-worth-the-extra-weight/ this test was with my little MYOG stove and a modified JB PCS pot, my conclusion was that unless it is very cold and fast boil times are important or you are on a long trip flux ring pots are not really an advantage.

For the last few winters I have used a Coleman xtreme stove with a JB GCS pot to cook in with great success but on my last snowshoeing trip (one night) we wanted to cook a nice meal that required two pots, 1.5 and 1 liter pot, before I went I added up the weight of my JB GCS pot and a 1 liter Al HD pot that fitted inside and compared the weight to my cheap Al pots of the same volume, the weight difference was more than an entire 170g Coleman Max canister, on this trip a fast boil time was not that important, so I went for the lighter pots and I did not need to use the extra 170g canister.

I have also done some work int heat loss from sides of pots but the results are not that scientific, http://tonysbushwalking.wordpress.com/2010/08/22/some-stove-windscreen-test-results/

Tony

3:43 a.m. on March 12, 2011 (EST)
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 For reasons unbeknownst to me MSR took the firefly off the market less than five years after introducing it. 

Ed

Ed,

 

The conventional wisdom is that the Whisperlite killed the Firefly.  The Whisperlite was cheap to buy -- and cheap for MSR to produce.  The Firefly was more expensive, and in some ways (with it's odd "pie pan" windscreen and aluminum parts) less robust than the cheaper Whisperlite.

 

HJ

8:07 p.m. on March 13, 2011 (EDT)
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 For reasons unbeknownst to me MSR took the firefly off the market less than five years after introducing it. 

Ed

Ed,

 

The conventional wisdom is that the Whisperlite killed the Firefly.  The Whisperlite was cheap to buy -- and cheap for MSR to produce.  The Firefly was more expensive, and in some ways (with it's odd "pie pan" windscreen and aluminum parts) less robust than the cheaper Whisperlite.

 

HJ

Yea, the wind screen was both bulky and lame: I replaced it with my own design.  The other aluminum parts have never been an issue, however.  Thirty five years of dependable operation under all conditions imaginable, and plenty of user abuse testify to its durability. The firefly is a stove capable of doing real cooking.  You could run it at a sustained candle flame, or raise the heat until maxing out with a roaring red hot jet blast - way hotter than the whisperlite.  I can make perfect pancakes and crepes with no scorching, or stir fry cooking for six using a large wok.  The only backpacking stove I know with such versitility is the legendary Optimus 00 series model.  The whisperlite is really only a water boiler, since it is nearly impossible to use for simmering.  I would have switched if I thought the whisperlite was better; but even my companions with whisperlites prefer the firefly.  I liked it so much that when it went off market I bought up all the maintenance kits I could find, to assure the stove will last me a lifetime.  Simply put: MSR blew this call.

Ed

9:05 p.m. on March 13, 2011 (EDT)
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Ed,

Your making me dislike my Whisperlite and I've never even used a Firefly.

Simmering with the whisperlite is frustrating, and wastes fuel if you use a steel plate or riser to reduce heat to the pot.

10:07 p.m. on March 14, 2011 (EDT)
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..Simmering with the whisperlite is frustrating, and wastes fuel if you use a steel plate or riser to reduce heat to the pot.

May I suggest looking into the MSR Dragonfly stove.  This stove is similar in functional design features with the Firefly.  I assume it performs similar to the Firefly too, as comment in the review section of Trailspace bears out.  The Dragonfly is not the lightest stove, but everyone reviewing it seem to believe it is worth the weight.

Ed

11:03 p.m. on March 17, 2011 (EDT)
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In the end I am happiest when I can eat well with the least amount of trouble. Weight, boil time, & fuel consumption aren't always my biggest concerns when I'm cold and hungry. Ease of operation and reliability has a lot of value as well.

 I feel like I have been camping with all of you. haha.

I have used more liquid fuel stoves than cansiters over the years and every time I go with someone who brings their cansiter stove, they start eating well before I do.  However, I can melt snow at over 10,000' and they don't.

Last summer on Mt Rainier, we had two msr wisperlights with two different pots. Snow melt time was considerably different.  The wider pot filled up the windscreen space and melted snow faster than a tall, narrow, coffee pot style pot. Both pots were light weight aluminum with lids. Even by squeezing the windscreen closer to the tall pot, it was the slower to melt snow.

5:30 a.m. on March 20, 2011 (EDT)
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..Last summer on Mt Rainier, we had two msr wisperlights with two different pots. Snow melt time was considerably different.  The wider pot filled up the windscreen space and melted snow faster than a tall, narrow, coffee pot style pot...

I found a wok was the most efficient snow melter, but since virtually all woks are steel, and relatively bulky, this performance has it drawbacks.  A covered aluminum frying pan works almost as well, but is hard to avoid spills, due to the geometry of this utensil.

Ed

6:53 p.m. on March 20, 2011 (EDT)
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..Simmering with the whisperlite is frustrating, and wastes fuel if you use a steel plate or riser to reduce heat to the pot.

May I suggest looking into the MSR Dragonfly stove.  This stove is similar in functional design features with the Firefly.  I assume it performs similar to the Firefly too, as comment in the review section of Trailspace bears out.  The Dragonfly is not the lightest stove, but everyone reviewing it seem to believe it is worth the weight.

Ed

Thanks Ed, I just may do that. I am currently on a tight budget but I would like to get one before this fall and the upcoming winter.

I like the canister stove I have for its simmering capability, but I'm definitely a white gas guy in winter. Not to mention I just like liquid fuel stoves for some reason.

7:51 p.m. on March 21, 2011 (EDT)
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GSI makes 2 sizes of wok that are anodized aluminum. They work well enough that we even use ours at home instead of our genuine Chinese steel wok.

There is a problem with the Dragonfly that has led to my leaving mine on the shelf almost permanently. And that is the very feature that makes it so good for simmering, namely the needle valve. If you do not do the shutdown correctly (that is, per the instructions provided with the stove), you will have to do frequent maintenance overhauls (less than 10 hours burn time), at least for the needle valve itself. A couple of acquaintances did a ski tour across Greenland about 15 years ago, shortly after the Dragonfly was introduced. Halfway through the tour, their Dragonfly utterly and completely failed. Luckily, they had an XGK with them, which served as the expedition stove the rest of the trek.  The problem is this - if you do not shut the stove down properly, you end up with fuel in the line, and in particular in the needle valve area. The lighter part of the fuel evaporates first, leaving the heavier "lacquer" components behind, particularly in the needle valve area. You notice this by a significantly increased heating time. At that point, you have to completely disassemble the needle valve assembly and clean the "lacquer" off the needle (pay particular attention to the grooves where the fuel flows through, but don't neglect the threads).

By following the proper shutdown procedure, you can lengthen the time between cleanings. Most people just close the needle valve. Instead, you should shut the stove off at the pump valve, leaving the needle valve open (preferably fully - to reduce fuel consumption, anticipate when the meal is done or the lead time for a full rolling boil). Then let the flame burn down until it becomes a "yellow" or "carbon" flame. At this point, blow the flame out. This allows, (1) the fuel in the fuel line to be pushed out, including the less volatile components (the "lacquer"), and (2) by blowing the "carbon" flame out, you reduce the deposition of soot in the jet orifice. This procedure also reduces the chance of disconnecting the hose with the pump valve still open, which spews liquid fuel all over the place.

I would actually recommend the MSR Simmerlite over the Dragonfly, or better yet, the XGK (current version, the EX, for expedition, has a very sturdy pot support and leg system). True, the XGK doesn't simmer very well, but with 80 or 90 percent of backpacking "cooking" being boiling water for coffee, tea, hot chocolate, or to rehydrate freeze dry, few people simmer in the backcountry anyway.

9:02 p.m. on March 21, 2011 (EDT)
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Well....thanks Bill, actually I think I remember you posting that once in the past, or maybe the same problem with another stove.

I have used the XGK although I don't own one, they are one heck of a stove from what I read. The one I used was a real powerhouse.

I would like to simmer because I like to cook real meals on trips where it is possible, I am trying to get good at cooking breads. Emphasis on "trying".

 

 

 

10:06 p.m. on March 21, 2011 (EDT)
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Bravo for the stove testing and many thanks!

My 2 cents :

I totally agree that running a stove at maximum output, specially the white gas variety, is a waste of fuel in normal conditions. The results on alcool stoves also matches my observations in the field : the height of the pot above the stove and the windscreen are the big factors, not the heat output IMO.

But there are two factors i think are worth taking into consideration:

I've found that under very cold (-25C and below on an XGK-EX) or windy conditions maximum heat output is the most efficient way of getting anything done. Forget simmering, you're lucky if you get a boil on a pot bigger than 4 liters. I am curious to see at which temperature going full-on becomes more efficient, i'll try to test it in the field.

Also, a stove may lose power due to poor maintenance, clogging or bad fuel. Having a bit of power in reserve is a good thing in these situations.

PS: Who cares about the noise when you've got 2 hats, a hooded down parka and 50 km/h wind flapping the tent :P

 

6:52 a.m. on March 22, 2011 (EDT)
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GSI makes 2 sizes of wok that are anodized aluminum..

..I would actually recommend the MSR Simmerlite over the Dragonfly...

Thanks for the wok info, and elucidating us about idiosyncrasies not mentioned in the reviews of the Dragonfly stove.

Ed

July 26, 2014
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