Not being a Trangia user, my understanding was that adding the water had the goal of reducing blackening of the pot. Did you observe any significant differences depending on the % water added?
how about some research on blister prevention
Franco wrote:Hi Tony
Reactor
Roger Caffin has reviewed the stove for BPL (http://www.backpackinglight.com/cgi-bin ... art_1.html, you need a subscription) but this is his brief conclusion :
It is a somewhat dangerous stove for carbon monoxide emission. It can't simmer, and it is not designed for use at or below freezing -
Franco
I guess you could repeat the tests at different temperatures (down to 0*)?
Also, the sooty pot would in fact heat quicker? Making straight metho more efficient?
I tried a MSR reactor stove last week, didn't last the week in real conditions, the jet must have blocked and couldn't undo the brass fittings in the field.... Also the thing slows to a crawl as soon as the temp drops!
Franco wrote:Hi Tony
That makes sense with the Trangia (over 50% of campers cooking inside the hut at Bluff (Vic) last w/e had them !) but I would still like to find out "scientifically" what happens when using a pressurised stove like the White Box and a relatively narrow pot . As you know I get a narrower flame adding water and that seems to make it more efficient.
Wow Tony, good post, very detailed...even if I did get a headache from trying to decipher the numbers
Franco wrote:Hi Tony
Thank you for that. I have gone the Caldera Cone way because I only boil water but the White Box stove results should apply to other similar designs like the very easy to make Supercat ( ?) . The various stoves I tried of that design (including a couple from Mini Bull) all had a too wide and mostly red flame .
Franco
http://jwbasecamp.com/Articles/SuperCat/index.html
Trangia :anywhere,anytime,every time.
Nuts wrote:That would be an interesting article, We use cannister stoves a lot and I have been searching for something more efficient in the cold. We use the MSR windpro and warm the canisters within a large heat shield with the stove. The reactor was very good...till the temp dropped and the jet blocked...
Irate Shane wrote:It appears the simple process of combustion is not understood and thus the methodology applied is wrong.
eddie the eagle wrote:Just noticed your density measurements, which I'm not disputing, as "the facts is the facts." Just a query, however, as something doesn't gel in a sleepy, dozy frame of mind. If pure metho has a density of 808g/L, and pure water at 20°C has a density of 996(?)g/L, wouldn't a 20% (v/v) mixture of water in metho give a density of 846g/L? I've been wrong before and I'll be wrong again, just an observation that didn't make sense on a first take.
[edit III - hydrogen bonding occuring between the metho and the water, decreasing volume? just a wild guess and a probably wrong.]
eddie the eagle wrote:
edit II: Just noticed your density measurements, which I'm not disputing, as "the facts is the facts." Just a query, however, as something doesn't gel in a sleepy, dozy frame of mind. If pure metho has a density of 808g/L, and pure water at 20°C has a density of 996(?)g/L, wouldn't a 20% (v/v) mixture of water in metho give a density of 846g/L? I've been wrong before and I'll be wrong again, just an observation that didn't make sense on a first take. [edit III - hydrogen bonding occuring between the metho and the water, decreasing volume? just a wild guess and a probably wrong.]
As you said, water plays around with flame temp at the expense of higher heat consumption (interestingly, not shown in your results - experimental error? loss of calorific value due to unburnt fuel/soot/higher carbon monoxide emission?)
The trangia has good conduction (transfer of heat from one thing to another - the aluminium's not bad at it and, as well,) there's not a lot of gap between the sides of the Trangia and the pot, allowing for a fair degree of heat transfer. To improve the heat transfer here, increase the residence time (increase turbulence.)
Tony wrote: Ethanol molecules are smaller than water molecules, so when the two liquids are mixed together the ethanol falls between the spaces left by the water. It's similar to what happens when you mix a liter of sand and a liter of rocks. You get less than two liters total volume because the sand fell between the rocks, right?
...there is some evidence that in some concentrations 5%-10% it may slightly enhance the efficiency
Orion wrote:The other way around. Ethanol molecules are larger than water molecules.
Did you do an error analysis? Just taking the standard deviations suggests that you do not have the data to make this claim.
Did you ever get around to posting the full details?
What temperature(s) were the fuels at when you measured their densities?
Tony wrote:I did repeat the tests for water Methylated Spirits several times and did similar tests with Methanol and IPA. They all showed similar trends that up to 10% water showed no decrease in efficiency and may actually improve efficiency slightly.
A possible explanation is in my previous post.
...as mentioned in a previous post the full written up results co-authored with Roger Caffin are on BPL who now owns the copyright.
Orion wrote:It seems reasonable that a lower flame would improve the efficiency. It's a shame that the two variables are confounded in your experiment. But if that hypothesis has merit then why wouldn't the effect also be present in higher water concentrations?
Darn! I'm very curious to see it but I'm too cheap to pop for the $25 membership. I'd rather spend that on unmethylated spirits!
I'm wondering a few other things though. How did you determine the water percentage? Did you measure it volumetrically and then determine the density, or was it the other way around. Your chart implies the latter but I don't understand how you could do this calculation without first determining the composition of the unadulterated fuel.
I'm also curious about the actual fuel volumes used, what you started with and what percentage was burned in a given test since that bears on the change in alcohol concentration.
I'd love to ask you a bunch more questions but maybe I should just go have a beer instead.
Bill P wrote:Thanks Tony,
I've used my Trangia since 1981 and my pots and kettle bear a nice matt black patina. I went walking with a bloke lake week using his newish Trangia (cos mine looked a bit sus) and he insisted on diluting the fuel in the burner pot with water. (hang on mate, its below zero outside, 1000m above sea level and you're watering down the fuel?) I'd never heard of this before and found it counterintuitive.
I thought his burner pot was harder to ignite from cold, taking several matches to light. Perhaps that's due to the lowered overall volatility of the fuel mix?
Also, do you have any hypothesis or thoughts on how much fuel is lost to evaporation when one extinguishes a hot burner? I've often wondered after what time interval is it better to let the burner run vs extinguish & relight, while swapping pots etc.
Bill P
Tony wrote:I made the mixes by weight, I find this is easier and more accurate than by volume. I mixed a range of mixes by weight and then measured density on a Anton Paar DMA 5000 density meter, I then made a chart of the results, as mentioned before the results are not as expected and the line was not linear.
I used 50 g of fuel to test. As can be seen in the results, with metho the tests used 12-17g of fuel, after the tests I weighed the remaining fuel then I took a sample for further analysis on the density meter, once I determined the density I then went back to the chart and determined the ratio of water alcohol remaining in the fuel.
Now there is a research project that I would love to do "what is the best beer for backpacking" maybe we can write a paper together on this one day, another project is "comparing US beers to Australian beers"
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