Someone on Whiteblaze said his method of determining the correct distance from burner to pot was to raise the pot until it stopped boiling and then lower it again slowly until the water begins to boil again. That height at which it starts boiling again is the correct height.
I tried to use my Flame-O-Meter to see what would happen if I tried that method. View the video and give me your thoughts.
I'm using a StarLyte Stove as my source of flame.
I read the article about fire. I learned (learnt, have learned?) in college General Metals class, in my Industrial Technology Bachelor of Science major, the hottest part of the flame is the invisible part just above the flame. Blue is hotter than yellow, but the hottest part of the flame is invisible and just above the visible flame.
I learnt (learned, have learned?) in White Blaze forum, the easy-method to find the hottest part of the flame is to boil water, then, lift the pan high off above the flame until the boiling stops, then, lower the pan, slowly, until the boiling starts and that "pan height" is at the hottest part of the flame.
We were discussing "pan height" for caldera clone design.
ConnieD » Mon Mar 15, 2010 2:04 pm Inquiring minds, like ours, like to know these things.. I know I do.
Nice find ConnieD. Here is an interesting part of what was said there:
Quote Apart from incombustible elements, the color of a hydrocarbon flame is primarily dependent on the richness of the flame - that is, on how much oxygen there is to combust the fuel. In practice*, when the mixture is slightly lean (has more oxygen than required for complete combustion), the color of the combustion zone is generally blue-violet due to large amounts of high-energy radical carbon and hydrogen compounds. When the mixture is slightly rich (slightly too much fuel and not enough oxygen), the color is sometimes green due to C2 molecules breaking free, and the high-temperature products can glow red from the CO2 and H2O produced during combustion. When the mixture is very fuel rich (a poor flame, with not enough oxygen to burn properly), carbon particles form and an intense yellow radiation results from their being heated in the flame. In very rich flames - often you see this in candles - soot particles may impart a black color to the outer edge of the yellow flame. Flame color comes from the energy released by the electrons of the atoms of burning gas as they are raised to higher energy states during combustion, then fall back to lower energy states. Some of this energy is released in the form of visible light. The color corresponds to frequency, which is a function of the amount of energy released. (Work with me on this.) Low energy, low-frequency light is red; medium-frequency, medium-energy light is orange, yellow, or green; and high-energy, high-frequency light is blue or violet. If the energy levels are spread over a wide range of the visible spectrum, the light will appear as white.
by ConnieD » Mon Mar 15, 2010 4:45 pm Ooh, then I should have got that right on the pop-quiz.
I answered, the hottest part of the flame is just above the inner blue cone, in the violet-blue, and then, it is light blue further out. He said, wrong!
I thought this part of that link is interesting:
"Provided your backyard lighter flame is free of contaminants that might skew the color, a slightly lean violet-blue flame is the hottest. Blue-violet = high frequency = high energy = high temperature. A white flame has its visible radiation energy spread out more evenly across the spectrum and isn't peaking on the high-energy blue end. That indicates lower overall energy, and thus lower temperature, than a blue flame."
"Many thermodynamics and chemistry texts state that adiabatic flame temperature is highest when the flame is at perfect stoichiometry (exactly enough air to burn the fuel). Since mixing and other practical effects require extra air to ensure combustion, the hottest flames in practice tend to be slightly lean (slightly more oxygen than needed)."
What has me going on this topic is that not so long back I saw an article about stove height and alcohol stoves at http://www.backpacking.net/bbs.html and the best results were about .75-1.25 inches above the flame.
a couple points. i'm not sure that useing a glass pot is the right thing to do for this. glass is a great insulater. slow to heat and slow to cool, so you are getting a delayed reaction as you raise and lower the pot. also. it's been determined time and again that slower is more efficient. pot hieght can be used to slow the burn and make use of all available btu's. the hottest point of the flame may not be the most efficient.
I'd think that things might go quicker toward an answer with multiple stove/pot setups. Set up 3 (or 5) as close to identical set-ups - vary only one component per test. First test pot height - one at 1/2", one at 1", one at 1-1-2" (maybe one at 3/4" and 1-1/4") - same quantity of water and fuel in each. Light 'em up and may the best stove win. Simultaneous testing would narrow down the critical parameters pretty quickly. Do windscreen parameters in a similar manner.
The opinion of 10,000 men is of no value if none of them know anything about the subject.
- Marcus Aurelius---------------------------------------------
Okay, when I do the test again I'll get the water to boil, raise it to a height of 6 inches and then remove the heat source. Once the water stops boiling I'll replace the heat source and slowly lower the pot.
Does that sound more like what we want to do?
The person on Whiteblaze made it sound real easy for everyone to go through this process.
Thinking back on what we saw in the video, the water is still boiling at a height of 6". In my next test, when I replace the heat source and the pot is at 6" will it begin to boil again at that height? If I lowered it 1" will it boil at that height? How slow should I lower the pot, 1" every 15 seconds? 1" every 5 seconds? The car jack is holding the pot, I can control it to what every speed you want. Give me some input .
There may be too many factors to draw a curve and see the change: same stove, same fuel, same cooking pot, same quantity of water, same starting temperature water, same ending temperature water. and then, change the distance top of stove to bottom of cooking pot in increments.
The first reasonably correlated events I started to see (YouTube) were boil times for either 1 cup 50 F water, or 2 cups 50 F water.