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Old 11-11-2015, 16:30   #16
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Re: Stove Fuel Physics

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Originally Posted by mstrebe View Post
I had a friend who would drop a washer into his ceramic coffee cup and put that on his inductive cooktop. You want to see efficiency, that's it: Only the washer got hot, the coffee cup insulated it, and it would boil water in just a few seconds with the cup taking a long time to warm up. Perfect for coffee.
I'm definitely trying this. Assuming this needs to be magnetic grade stainless, how easy is that going to be to find...?
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Old 11-11-2015, 16:40   #17
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Re: Stove Fuel Physics

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I measured the time required to boil 2 cups of water on 4 different stove tops. Here are the results:

-------Stove--------------Heat Rating--------Time to Boil 2 Cups

Alcohol, Origo--------------(7,000 BTU)-----------5:25
Propane, GE-Household-----(9,500 BTU)-----------3:40
Electric, GE-Household------(6,150 BTU)-----------3:40
Butane, Burton-portable----(7,400 BTU)-----------2:20

Noteworthy was the inconsistent boil times vs. BTU rating of the stoves. For example,the Propane stove is rated at 9,500 BTU and the Electric stove is rated at 6,150 BTU yet both stoves had identical boil times.

Also, the Butane stove was more than twice as fast as the Alcohol stove yet they have similar BTU ratings.???

I used the same kettle for each test and the starting water temperatures were similar. Lowest altitude test (Alcohol) was 0 feet above sea level and the highest test (Electric) was 400 feet above sea level.

Does anyone have a good explanation for the above discrepancies?
Generally, you'd want to do multiple tests, repeating the same experiment while controlling for any variation as many times as you can stand it. Then take all that info and wave a magic statistical wand over it, calculate standard deviations and determine if there's any significance between them. Also, some fuels are more efficient than others. Ex. Butane is more efficient than propane, which might account for that difference Probably even more so compared to alcohol: http://sectionhiker.com/ultralight-b...g-stove-guide/
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Old 11-11-2015, 18:10   #18
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Re: Stove Fuel Physics

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Originally Posted by hpeer View Post
what temp was the water when you started?

I'd like to do a compare with our kerosene stove and a butane camp stove.
55 degrees Fahrenheit. Kettle has a thin, sheetmetal bottom so not a lot of mass in the kettle to heat.

Steve
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Old 11-11-2015, 19:05   #19
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Re: Stove Fuel Physics

I believe that stoves are rated purely on the rate of fuel energy consumed in BTU/hr (not uncommon to see sloppy terminology of BTU or BTUH shown, but they really mean BTU/hr). The efficiency of the heat of combustion going into useful heating of a pot or pan is not included. A lot of heat from a flame will bypass the pot/pan and just heat the surrounding air. So a lot depends on the size and shape of the burner, the distance that the pot/pan is held above the burner, and the size and material used for the pot/pan.
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Old 11-11-2015, 20:43   #20
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Re: Stove Fuel Physics

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Originally Posted by Dennis.G View Post
A lot of heat from a flame will bypass the pot/pan and just heat the surrounding air. So a lot depends on the size and shape of the burner, the distance that the pot/pan is held above the burner, and the size and material used for the pot/pan.
Hence the development of things like this:

https://www.washingtonpost.com/news/...r-save-energy/

"The secret to the Flare Panís energy-saving efficiency is a series of vertical fins that jut out along the outer surface in a circular pattern. The aerodynamic fins prevents heat from escaping by channeling it from the bottom and up along the side, where heat can evenly distributed across more surface area, allowing foods and liquids to warm up much faster."
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Old 12-11-2015, 03:02   #21
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Re: Stove Fuel Physics

Interesting stuff Steve. I've just switched to Origo methane stoves myself. Hopefully I'll be happy with the tradeoffs. Anyway, my first boat had kero, and she came with a fancy kettle that had a coil and heat trap at the bottom to help capture some of the waste heat. I've often wondered if some sort of heat shield like the MSR stoves have, or the jetboil system would improve efficiency enough to be worth the hassle.

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Old 12-11-2015, 04:29   #22
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Re: Stove Fuel Physics

As Pegu Club notes above, the fastest beat the slowest by 180 seconds. That is 3 full minutes. Per day! -- an hour and a half over a month and a full 18 hours over a year!!! If you're a worry wort captain of industry 18 hours sounds like a big waste of time when you could be making money.

But as O'Reilly would say, why go fast when you can go slow?

Stove Fuel Metaphysics

The fundamental structures of reality go beyond what even physics is capable of studying. Modern science has forgotten that humanity actually does possess a tradition of rigorous intellectual inquiry that has been able to probe, painstakingly and fruitfully, beyond physics.
http://www.catholicworldreport.com/Item/3333/metaphysics_and_the_case_against_scientism.aspx

And that's how I spend some of my 3 minutes per day. My up-and-at-'em routine is not to hit the deck running for a cuppa Joe. At a physical age of 73 (tho more than a half century younger mentally) I open my eyes and heart to the overhead, and thank the lesser gods for a calm night at the dock, or cuss them as the case may be. A brief assessment of the pain in my back is a daily reminder of a past slip in the shower as I move gingerly toward the Origo, turning on the mobile hotspot and laptop on the way. Water on, I stroll thru the main saloon toward the pee jug. I reflect that I only made this trek 3 or 4 times in the night. Not bad.

I stick my head out of the companionway and check the weather and whether my neighbor has deigned to wear her top this morning ... she's a free spirit, thank you Jesus, and I'm a freeloader.

By this time the water is hot, and I don't think I've wasted a second waiting for it. Life is good.
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Old 12-11-2015, 05:19   #23
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Re: Stove Fuel Physics

Read that to my wife, she laughed, thanks!
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Old 12-11-2015, 14:34   #24
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Re: Stove Fuel Physics

The point isn't really to save time but to save fuel: time is almost for free but fuel isn't.

And avoiding frequent refuelling stops isn't bad, too.

Alain
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Old 12-11-2015, 15:32   #25
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Re: Stove Fuel Physics

Interesting stuff. I tried to do the same test on our Kero stove and the time was dramatically different. About 8 min not including preheat. Water temp 51.

So something is wrong with my setup. I cook and bake just fine.

I wonder if there could be that much difference in a kettle, even though they look similar. I've never hard of someone complaining of a Kero stove being slow.

This kind of stuff is valuable because it starts to introduce some repeatable or measurable elements. I've never seen any one else's stove work so I have no basis for comparison.

Enlighten me someone, please.
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Old 12-11-2015, 17:43   #26
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Re: Stove Fuel Physics

Tried it with our gimbqlled butane camp stove and that was 3-1/2 min.

Cleaned the burner on the Kero stove but it made no appreciable difference.

It would be nice to see someone else try it on a Kero stove for comparison.
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Old 12-11-2015, 17:57   #27
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Re: Stove Fuel Physics

Using a washer in a cup on an induction stovetop sounds awesome, so I immediately tried different washers but none of them worked. I placed a stainless steel washer a bronze washer and then I tried a galvanized washer. I put them directly on top of the induction cooktop and moved them around. I then tried a steel hinge which worked. So I'm guessing the size is too small to make my induction cooktop start up. Any suggestions?
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Old 12-11-2015, 18:25   #28
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Re: Stove Fuel Physics

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Originally Posted by sparrowhawk1 View Post
Using a washer in a cup on an induction stovetop sounds awesome, so I immediately tried different washers but none of them worked. I placed a stainless steel washer a bronze washer and then I tried a galvanized washer. I put them directly on top of the induction cooktop and moved them around. I then tried a steel hinge which worked. So I'm guessing the size is too small to make my induction cooktop start up. Any suggestions?

The bronze definitely wouldn't work.
Did you test the SS and galvanised washers with a magnet?

Size is definitely a factor, as well as placement. Induction cookers generally contain one or more "pan size sensor" or "cookware auto detect" which detects the presence of a pot and how large it is. You would need to make sure that the washer is sitting over the centre of the element and that it is large enough to be detected as a "pot". So what works on one make of induction cooker may not work on another
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Old 12-11-2015, 20:37   #29
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Re: Stove Fuel Physics

Thanks Stu, I realized I shouldn't have tried bronze shortly after posting, but checking to see if the galvanized washer was magnetic didn't even cross my mind. I will check tomorrow if its magnetic like I suspect then will start experimenting with what size I need to trigger my stove. Maybe I need to do two mugs at a time each with a washer in it. I never thought I'd actually be looking for stainless steel washers that are magnetic. It's usually something I try and avoid, but I guess there's a place for everything in this world.
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Old 13-11-2015, 20:39   #30
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Re: Stove Fuel Physics

The data cries for extension...

.................................................. .......................Actual
.................................................. .......................Rate of
.................................................. ....................Heat Poured
.................................................. ....Time to ..... into Water
-------Stove-------------Heat Rating--Boil 2 Cups---by Stove

Alcohol, Origo-------------(7,000 BTU)-----5:25-----1740 Btu/hr
Propane, GE-Household----(9,500 BTU)-----3:40-----2570 Btu/hr
Electric, GE-Household----(6,150 BTU)-----3:40-----2570 Btu/hr
Butane, Burton-portable---(7,400 BTU)-----2:20-----4037 Btu/hr


This was done thus: 2 cups of water = 2 X 8 fl oz = 16 oz
= 1 lb water. Raise that 1 Fahrenheit degree => 1 Btu.

212 - 55 degrees F = 157 F degrees temperature rise.

Convert minutes:seconds to seconds, eg 3:40 => 220 seconds.
There are 3600 seconds in an hour.

OK then, Actual Rate of Heat = (157/220)*3600

There. How's about them apples....
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