More Foster’s Fun

[Glenn S]

Delmar, what other data you think should be included? I'm going with the assumption that water temp is the same as ambient temp. Thought just posting the final efficiency rating would be ample enough, given that we're all working off the same formula. No? Of course providing all that data would be useful for peer review I suppose. Would be interesting to see how alternate variables effect the results ie: wind, colder water, etc, but was hoping to keep things as constant as possible for a range of tests, at least for this experiment. Maybe some other additions with notes describing altered parameters would be in order. And 62% was one of the highs I've seen so far, possibly due to newly uncapped water. I've been hovering at the 60% mark though, yes. I questioned water quality effecting results in an earlier post, which is why I went with virgin water from a bottle, as it's replicatable.

(If my numbers show up in your spreadsheet, they're skewed. I posted earlier that the weight for my 15ml of fuel was listed incorrectly. It wasn't until I saw your post about the .789 figure that I got the correct weight. I've put that into the SS formula to prevent any future error.)

A dedicated thread for testing would be useful. If we ever get a big enough pool of data, it can easily be pasted over as well. Should I post the formula that I morphed from Bens SS that have (the one on my phone) for review/duplication? It's only 2 cells of formulas with 5 cells of variable entry.

Dan, some assumptions have to be filled in for missing data. Boil time being a main one. But guestimating at a 10 minute boil time, with your run out at 90 seconds later, using 710ml of water (3 cups), I come up with an efficiency rating of 62.6%. Would be curious to see the results from a 500ml boil.

[Delmar O’Donnell]

> Hey statistics guys…..I've been able to boil 3 cups of 50 degree water in 40 degree ambient air temps using the Conquistador pot and new windscreen design on 25ml of denatured alcohol. How does that come out on your charts? I used the 3cup capacity flat bottom beer can pot. The one with the cool graphics :-) Oh, forgot to mention that the water continued to boil for 1.5min until flame out. Did 3 tests, all were approx the same results. Test were conducted in my cold garage.

What's missing is time-to-boil. I've got the rest entered, so lay it on me.

PS: You're boiling 3 cups water in a 3 cup capacity pot?

[Delmar O’Donnell]

Glenn, I'm a fan of how David posts his data, and was thinking I'd publish my results likewise…raw data, so anybody can calculate and verify. You KNOW how easy it is to make a mistake, what with all the conversions and what-not. And with Bob visiting the thread, he's certain to spot as much as a misplaced umlaut or an error into the ten-thousandths. Which is actually good for this sort of pursuit.

At this point I find I'm clicking from thread to thread to follow the stove efficiency data in multiples, and was thinking how nice it would be in a single thread, with guys trying to improve their efficiency scores and sharing tips on what works.

A big thanks to Ben for the spreadsheet that allows an efficiency calculation. I'd have never been able to create such a SS on my own. I never even heard of "Lower Heating Value" etc in my life. But thanks to his spreadsheet, calculating the efficiency percentage is easier than baking cookies!

PS: Ambient Temps. It's not factored into Ben's formula…yet…who knows but he'll come out with a revised SS with such parameters. BUT, as the calcs get more complicated (having to measure fuel temp, etc) I can guarantee fewer people will go to the effort. The current SS is pretty simple.

PPS: As far as publishing…if you and Ben are cool with it…then why not?

[Bob Gross]

"You KNOW how easy it is to make a mistake, what with all the conversions and what-not."

I thought that I made an error one time, but I was mistaken.

–B.G.–

[Glenn S]

Fair enough. Updated my test parameters to reflect boil and burn times. I agree that peer review and critique should be an important factor if we ever hope to achieve any degree of reliability.

It sounds like that formula is pretty common knowledge to those in the know, but I'm not one of them. I don't think the formula is any big secret really, at least IMO. Since Ben offered to mail it to anyone that asked, it didn't sound as if he would mind much either. I'll work on posting it, and if he hollers at me, I'll just pull it down.

Oh, and who's Scott? ;)

[Delmar O’Donnell]

Geez, my imaginary friend I guess. Edited. Sorry.

Glenn, don't you want to post fuel amount?

…and also amount of water you're boiling.

[Dan Yeruski]

Delmar here is the time to boil:

Water boiled at approximately 11-1/2 minutes for all 3 tests.

[Delmar O’Donnell]

Dan:
Boil at 11:30,
burns till 13:00,
Fuel 25 ml
Initial temp of water 10 C
Water amount 710 cc
Efficiency: 61.6%. ….Impressive!!

I think Dan and Glenn belong to the exclusive "sixties" club.

[Glenn S]

"500ml of water and 15ml of Sunnyside Denatured Alcohol fuel will be used in each burn."

Second paragraph?

[Delmar O’Donnell]

Glenn: And there it is. I was looking only at the line with the data.

I entered your data above ^ and came very close to your calc at 61.3%. Muy impressive.

Question. Ben's SS wants the amount of water in grams. I have been entering ml/cc. Is that kosher?

Gram is weight/mass, but ml/cc is volume … so… 1 cc of water at 4 C / 39 F is 1 gram … is an adjustment necessary, or is putting ml/cc in the SS close enough, in the typical testing ranges (say, 40-70F)?

[Glenn S]

gram = ml

I've entered my spreadsheet morph into my post above now too.

Curious why you came up with a point 3 instead of point 7 percentile. I just double checked again with the original SS from Ben, and I still get 61.7%. Hmm…

[Delmar O’Donnell]

Gram = ml at 4 degrees C.

So I think I got this figured out…maybe, not confident…had to do a regression based off a scrap of info I found at a low quality inet source, but it looks like we lose -.0014 of a gram for every 1C increase in the temperature of 1 cc of water.

I don't think that's worth adding a correction to the SS, do you? Decimal dust.

Dang it, where is an engineer when you need one?

[Glenn S]

Then you'd have to start factoring in sea level too lol… I put 500 grams on the scale, pour it into a measuring container, and it says 500 ml. I think we're fine just saying g=ml

Besides, as long as everybody agrees, then we're all playing by the same rules anyway. If we start hitting above the 90% range, we can begin worrying about such miniscule variances.

PS: I think the probe in the water is going to have a bigger effect than that little variation.

[Delmar O’Donnell]

True that.

The guys at altitude will have an advantage.

[Delmar O’Donnell]

Glenn, my lab partner: Thanks for posting a compiled version of the calc, this is great!

[Ponderous discussion resolved and removed for clarity.]

[Glenn S]

Ben's shows fuel to boil (FTB) in grams for both quantity used, and in how much to boil. I'm showing in ml for both. Hence the different display between the two. Whatever formula Ben uses works off weight, so I had to convert from a ml entry to grams for the formula math, then back to ml again for display.

You are correct if you wish to see how many grams of fuel it took to reach a boil. I just don't have anything that will weigh that small, so I stuck with liquid measurements for both fuel cells.

If you divide the FTB by the fuel used in each SS, you will get the same percentages in each. (Provided each SS uses either g or ml for BOTH fuel parameters – can't mix 'n match and get equal results.)

Edit: And yes, F is more accurate than whole number C, but grams to the hundredth is more accurate than ml… Sooo, comes a point when ease of use rules out, especially for a simple garage mechanic like me lol But there's no stopping the evolution. I'm open to upgrades and further refinements.

I've also edited the formula in my post to the C8 entry with the (ml) annotation for clarity. Good catch :)

[Bob Gross]

"F is more accurate than whole number C"

Don't try to confuse accuracy with resolution.

A Fahrenheit thermometer is likely to be just as accurate as a Celsius thermometer, but Fahrenheit degrees are smaller units than Celsius.

No umlauts were harmed in the creation of this posting.

–B.G.–

[Glenn S]

Hence the criteria "whole number", rather than fractional readings. ;)

[Delmar O’Donnell]

OK, I get it Glenn. You're showing FTB in ml not grams. Yes, I had noticed your formula arrived at the same efficiency percentage, via a different FTB amount. So I'm going to go back and edit out my previous objection, so as not to confuse other viewers.

Again, good work! You've made a nice, short, easy to duplicate spreadsheet of just 7 lines that allows us to make much more controlled and objective comparisons. I suppose someday the SS may be updated with other variables, such as elevation, but that's beyond my pay grade.

And thank you, too, Ben, for the vital formulas and constants…you still out there?

.

[Glenn S]

Oh, there's still a good deal of squirrelieness in the formula. Like, being able to enter a burn time that's shorter than a boil time and still have a positive efficiency rating.

But it's the best we have so far, and it makes relative comparisons at least doable.

Ben must MIA for a bit. Hopefully out on a trail.

[David Gardner]

Hey guys, I can't seem to get a hold of Ben's SS. Can I get a copy?

Thanks.

[Ben H.]

Sorry for going MIA on you guys. Unfortunately I wasn't on the trail. I was a judge at the LA County Science fair on Friday and then spent the weekend chasing my kids. Let me know if you have any question left for me.

[David Gardner]

Parameters:
400 g of 70* F water
15 ml of Klean Strip denatured alcohol
57.8* F air & surface
No wind
29.52 inHg barometric pressure
65% relative humidity
16 oz brushed Al beer can (bottom half chemically blackened)
Windscreen = unpolished Ti
Base sheet = polished Al
Refletix floaty
Stove = Ramjet XUL
Oversize Al pot lid
Boil measured at 212* F

Setup:

Results:
6:18 min boil, 9:13 min burn
6:21 min boil, 9:16 min burn
6:15 min boil, 9:10 min burn
6:25 min boil, 9:18 min burn
6:14 min boil, 9:04 min burn

Average boil = 6:18.6 min, max deviation 11 sec = 1.5%
Average burn = 9:12.2 min, max deviation 14 sec = 2.5%

Efficiency = 65.2%

I think the Reflectix floaty helped a lot.
[edited to change picture so reflectix floaty shows more clearly]

[David Gardner]

Anyone out there have any groundbreaking brainstorm ideas about ways to achieve 75% efficiency with an alcohol stove? I've tried just about everything I can think of at this point.

Some kind of heat exchanger a la Jetboil maybe? Ceramic coating on the inside of the windscreen? Radiator fins on the sides of the can?

Help!

[James Marco]

Ground Breaking? Ha, ha, no.
Your goal is to extract ALL the heat from a flame, slowing down the heat till it has a chance to transfer to the pot of water and minimizing heat losses.

Here are some things that will help:

1) Burn slower: I built some sroves with a 1/2" outlet to slow the burning down. This gives the conduction in the water, metals, and air more time to work without wasting heat. (I have found a 10-12 minute, 2 cup boil to be a fairly good time, but this is a compromise between heat lost and time to boil…) Coralory the fuel must burn efficiently, not with any soot.
2) Focus the flame in the center of the pot, at the first "baffle", if you will.
3) Keep the non-heated surfaces from conducting heat. Conduction is a two way street. The blued ti on the cone shows where heat is being lost, for example.
4) Paint or anodize the pot black. Polish any non-conductive surfaces.
5) Wrap the cone, pot and upper pot with some sort of efficient insulation, ie, minimize waste. Fiberglass works well for tests.
6) Use baffles/heat exchangers to mix air causing heated air to mix with air that has already transfered heat to the pot. Excess heat around any heat exchanger can be used to heat the water.

I test mine by placing my hand on the pot top. If you can feel heat from the stove, you are loosing heat that can make the water hotter. If it is just heat being re-radiated from the pot/water, you need insulation. Note that you will always get some heat, this should be just warm and is a product of the differential between good heating and cold water. You should get around 80-85% efficiency this way. Is it good for camping? Likely not. Too slow and too many fiddly parts. I was getting around 10gm of fuel(SLX) for 50-200F of 2 cups of water in 15 minutes. Or about double what I was getting with the SVEA (about 9-12gm of fuel for 1Liter in 10 minutes…~1/3oz)

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