Originally Posted by
cyccommute
You can't burn a lower heat content fuel at twice the rate and transfer heat faster by just making the pool of fuel larger. First, the fuel has a specific amount of heat per mass. If it has less heat per mass, you have to burn more of it to transfer that heat. If you make a large pool of it, you just lose more of the heat to the surroundings. You also have mass transport problems with larger pools of fuel. The yellow flame of your picture and the sooted bottom of the pot indicate that you aren't burning the fuel efficiently because the fuel isn't getting enough oxygen.
There are natural laws that you simply can't violate which dictate how much heat a substance has and how fast that heat can be delivered. You can't break them or even bend them. You may think you have bent them but you really haven't. You are likely comparing caulk to cheese by doing a poorly controlled experiment. You can compare the fuels and the heating rates but you need to use equipment that is the same or at least similar enough to give you a meaningful comparison.
I don’t think I am breaking any of the laws of thermodynamics, but who knows perhaps I am on the edge of creating cold fusion (Silliness). We are comparing fuels and not stoves. There are lots of variables that I am assuming to be neutral. Things like complete combustion, similar flame patterns and size relative to the pot and optimum height of the pot off the flame which I have found changes with different stoves. I don’t have the expertise, the equipment or the desire to pin everything down to exact scientific results, just want see what the general trends are.
Originally Posted by
cyccommute
Let's not wander off into silly territory. Sticking to the point of liquid fuels used for camp stoves, there is definitely a difference in the energy transfer between ethanol and kerosene and the equipment used to burn the fuel. For example, kerosene used in a Trangia would provide more heat than ethanol because it has a higher amount of energy to give up. In an open burn situation, however, the amount of oxygen getting to the fuel would be limited and it would burn cool. It would produce lots of unburned carbon which is an indication energy loss. Pressurize it, atomize the fuel and efficiently mix it with oxygen and you can capture nearly all of the energy the fuel has to offer.
On the other hand, if you were to do the same with ethanol, i.e. pressurize it, atomize it and efficiently mix it with oxygen, you would see a gain in capturing energy but there isn't as much to gain as hydrocarbon fuels. Your fuel is partially oxidized and therefore doesn't has as much energy to give up.
Thank you for noticing my silliness – it is not always recognized. I don’t think anyone is advocating nuclear fission for camp stoves. But, you could probably boil a pot of water in one nanosecond, and there would be no soot on the bottom of the pot. There are a number of pressurized alcohol stoves on the market. I’ve never used one.
Originally Posted by
cyccommute
I hate to break this to you, but most of the alcohol fuels you are likely to use, outside of something like Everclear, are produced from petroleum. Drinking ethanol is made by biological processes and has been for millennia. But commercially produced ethanol that is use in denatured ethanol is made through refining and cracking and treating oil.
Yes that is true for many denatured alcohol brands. Some of the really “bad” stuff is less than 25% petroleum based ethanol with the remainder being fossil carbon based methanol and various recycled solvents turning your stove into a little toxic waste incinerator.
But the Alcohol I am most likely to use is Klean-Strip Green Denatured Alcohol – 95% Natural, Renewable and Biodegradable Content. You can pull the MSDS if you need further proof. It is widely available in the United States at home improvement stores like Lowes and Home Depot. Many small town ACE hardware stores carry it. I bought the quart I used for my tests listed below at my neighborhood Fred Meyer grocery store (Kroger’s). I have never had access to it, but I have been told in the Midwest you can burn E-85 in alcohol stoves and E-85 is 85% grain based ethanol. I read that the gasoline content burns out of it fairly quickly and you notice some heat drop when it does.
I don’t know the availability of renewable ethanol around the world. I would suspect it would be readily available in South America with Brazil being the largest ethanol producer in the world. Another benefit of using bio-ethanol is the smug knowledge that in the US it is subsidized by automobile and RV owners, and in some very, very small way you are not adding to global warming.
Below are some burn and boil test done on 12/3/2012 on various stoves. In the photo they are L-R a modified Packafeater XL (55 g & my current touring stove), Cat-can Trangia(140 g & used on many tours), Cat-can Sheba (120 g & never intended for touring). To the rear is the Optimus canister burner in a Trangia 25 base (220 g in the Cat-can version & never used on tour) and my T-25 kettle, which was used for all bloom to boil tests. Mother Kenmore is holding them all up ( fuel by 100% Columbia River Gorge wind generated 220 volt single phase-50 amp electricity ).
The results generally hold up my and other's statements on the efficacy and efficiency of non-pressurized alcohol stoves while not refuting any of your claims as to the heat density of fossil camp fuels or soot on the pot bottoms.
[TABLE="width: 500"]
[TR]
[TD]*[/TD]
[TD]Packafeather[/TD]
[TD]Trangia[/TD]
[TD]Sheba[/TD]
[TD]Optimus[/TD]
[TD]Kenmore[/TD]
[/TR]
[TR]
[TD]Boil 500ml[/TD]
[TD]4.9[/TD]
[TD]4.5[/TD]
[TD]3.1[/TD]
[TD]2.8[/TD]
[TD]1.8[/TD]
[/TR]
[TR]
[TD]Burn Time[/TD]
[TD]17.0[/TD]
[TD]26.0[/TD]
[TD]14.0[/TD]
[TD]N/A[/TD]
[TD]N/A[/TD]
[/TR]
[TR]
[TD]Fuel Amt ML[/TD]
[TD]60.0[/TD]
[TD]120.0[/TD]
[TD]120.0[/TD]
[TD]N/A[/TD]
[TD]N/A[/TD]
[/TR]
[TR]
[TD]ML/Min[/TD]
[TD]3.5[/TD]
[TD]4.6[/TD]
[TD]8.6[/TD]
[TD]N/A[/TD]
[TD]N/A[/TD]
[/TR]
[TR]
[TD]ML to Boil[/TD]
[TD]17.4[/TD]
[TD]20.8[/TD]
[TD]26.4[/TD]
[TD]N/A[/TD]
[TD]N/A[/TD]
[/TR]
[TR]
[TD]Oz to Boil[/TD]
[TD]0.6[/TD]
[TD]0.7[/TD]
[TD]0.9[/TD]
[TD]N/A[/TD]
[TD]N/A[/TD]
[/TR]
[/TABLE]
* Of course ignition to full flame is nearly instant with the Optimus and I didn’t time ignition to bloom time on the alcohol burners. In relative terms the Trangia was 15 to 20 second faster coming to full bloom than the Sheba and both were considerably faster than the Packafeather. But because the market only seems to advertise full throttle bloom to boil, I timed this “market speak” standard. Speaking only for myself, a better and more poetic standard is the time from when I dig my cook kit out of the bottom of my pannier until I am sitting comfortably on the river bank enjoying a cup of tea and taking in the sunset, because this entails setting up my tent and sleeping situation and other transitional tasks at the end or beginning of the day’s ride, bloom to boil time becomes a back ground concern at most. It is certainly less of a concern as waking up my campground neighbors at 5:30 in the morning with the howl of a pressurized stove.
During these tests a small flame appeared at the burner end of the Optimus hose. I have used this burner less than a dozen times, never while cycling. Inspection revealed a serious crack in the swaged hose-end clamp. The flame was small and was put out safely by a turn of the valve. What if the identical clamp on the canister end of the hose was throwing out a larger flame directly onto the fuel canister? Now this is a specific safety failure to a specific model burner, but the more general issue is the greater complexity of the system the greater chance of failure be it safety or just general functioning, and the greater quantity and energy density of the fuel, the great the danger if failure does occur.