Most efficient alcohol stove?

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zelph
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Re: Most efficient alcohol stove?

Post by zelph » Wed Oct 22, 2008 9:52 am

Here is a little of what it says:

Use the test spreadsheet to determine the amount of alcohol fuel that you will need for the test burn.

• You will need to measure the starting temperature of the water and input this figure into the highlighted cell (line 13) of the spreadsheet.

• You will need to measure the expected final temperature of the water and input this figure into the highlighted cell (line 14) of the spreadsheet. If you live at a higher altitude, consult the “Altitude and Boiling Point Chart” at the bottom of the attached spreadsheet for an altitude-corrected boiling point.

• You will have to input the amount of water that you will use for the test into the highlighted cell (line 17) of the spreadsheet.

• Measure out the specified quantity of alcohol fuel needed for the test. (Line 24, 28, 32 or 36—depending on the type of alcohol you will be using.)

(The spreadsheet will automatically calculate the amount of alcohol fuel that you will need to run the test. Use the figure that is generated for the type of alcohol that you will be using…methanol, iso-propanol, denatured alcohol or ethanol.)

• Set up your stove system, fill your pot/pan with the measured quantity of water, insert the thermometer, add the calculated amount of alcohol fuel to your stove and fire it up.

• Note the final temperature of the water after the fuel burns out.

• The final step to determine the efficiency of the stove system under test is to enter the “Actual final water temperature” into the highlighted cell (line 18) of the spreadsheet. This will generate the “Actual % efficiency of the stove system”.

The following formula is used in the spreadsheet to calculate the efficiency of the stove system:

(Final temperature of water- Initial temperature of water)/ (212 F - Initial temperature of water) = % efficiency.

If the final temperature is, for example, only 60 degrees F, and our starting water temperature was 34 F, then the stove system is only 14.6 % efficient.

(60F-34F)/ (212F-34F) = 26/178=0.146 or 14.6%

Test results:


I tested 4 types of stoves, (shown above) :

• A Goya stove system, which uses a Pepsi can soda, stove insert.
(Check out atraildreamer’s project at http://www.backpacking.net.)

• A stove made from the bottom of aluminum Budweiser bottle.

• A cat stove that had 16_ ¼” holes in the top row and 11_ ¼” holes in the bottom row.

• A “Double Cat” stove, which is a 3” cat stove that is glued into a 5” cat food can that has 2 rows of 1/4 “holes punched every ½” around the larger can.


All tests, not including the “Double Cat”, were conducted with 16 ounces of refrigerated water at 40.5 degrees Fahrenheit. Inputting the amount of water and the initial temperature into the test spreadsheet generated an amount of 12 ml (cc) of Heet Yellow dry gas (Methanol) for the test burn. An Imusa grease pot (3 cup capacity) was used for the tests.

Initial test results:

Amount of Starting H2O Final H2O System Fuel Fuel
Stove System: H2O used: Temperature: temperature: efficiency: used: amount:
(Ounces) (Fahrenheit) (Fahrenheit) (%) (ML/CC)

Goya/Pepsi 16 40.5 136.3 55.9 Heet (Yellow) 12

Cat stove 16 40.5 122.9 48.0 Heet (Yellow) 12

Bud bottle 16 40.5 136.0 55.7 Heet (Yellow) 12

The Goya system gave the best initial efficiency of the three tested at 55.9%, with the Bud bottle stove coming in a close second at 55.7%. The cat stove was the easiest of the three to construct, and considering that it is not the best example of the cat stove design that is posted on the various forums; it gave a respectable 48% efficiency.

Some surprising test results:

A second round of tests was conducted, including the “Double Cat” stove. (The Double Cat stove is a 3” cat food can stove, which was glued into a larger 5” cat food can. Two rows of ¼” holes were punched into the side of the larger can with a spacing of ½”. Each the rows were about 3/8” apart).

(For the second test enter data into lines 68, 69 & 71 of the spreadsheet and use the fuel amounts listed for your fuel of choice on lines 56 through 64 of the spreadsheet. Variations in the initial and final temperatures of the water are allowed, but the same amount of water used in the initial test must be used in the second and third test burns. In other words, if you initially tested 16 ounces of water in the initial test, use 16 ounces of water in the follow-up tests).

On the second test burn, after factoring in the initial efficiency, the Goya stove system, actually showed a decrease in the efficiency of the system to 48.3%, down from 56.8%, and a lower than expected final temperature of 186.5 F! This decrease in efficiency apparently is the result of the larger quantity of fuel causing a higher pressure to be developed in the Pepsi can. This resulted in a more aggressive flame pattern that extended farther out of the Goya stove system heating the surrounding air, rather than the grease pot. A third test, using 24.5 ml of fuel got the water to 199.9F at an efficiency of 44.9%.

(For the third test, enter the data into lines 98, 99 & 101 and use the fuel amounts listed for your fuel of choice in lines 80 through 94).

Actual boiling conditions (where actual steam was observed coming out of the grease pot) required 26.4 ml of fuel, which pushed the water to 214.5 F at an efficiency of 45.5%. The 214.5 F temperature, which is 2.5 F above the normal sea level boiling point of 212 F, can be attributed to a slight “pressure cooker” effect caused by the tight-fitting foil covering the grease pot.

(The amount of fuel needed to heat the water to a steaming boil can be found for your fuel of choice in lines 110 through 124 of the spreadsheet. These quantities are calculated by combining the test results of the three burn tests.)

The cat stove showed an initial efficiency of 56.8%, dropped to 48.6& on the 2nd burn, and went back up to 56.1% on the 3rd burn, another unexpected result!

The initial Double Cat stove test showed an efficiency of 55.6% with a final water temperature of 135.2 F, but the burn took 17 minutes to complete on 12.1 ML of fuel! This should be of interest to trail cooks who like to slow-simmer their meals. The grease pot sitting on top of the Double Cat restricted the airflow causing the long burn time. A repeat of the test, using a hardware cloth wire mesh screen (borrowed from the Goya Stove system) sitting on top of the Double Cat resulted in a pitiful efficiency of 31.7%, with a final water temperature of 93.9 F, and a burn time of 8 minutes. The wire mesh apparently disrupted the laminar flow properties of the inner cat stove and allowed too much air into the system resulting in the lousy results.
Stove Type Fuel Fuel Amt (Oz) Starting Goal Final System
Type: of Test: Used: AmT (ML): H2O used: Temp (F): Temp(F): Temp(F): Efficiency:

Goya/Pepsi Initial Heet (Yellow) 11.9 16 41.5 212 138.3 56.8%

Goya/Pepsi 2nd burn Heet (Yellow) 21 16 41.5 212 186.5 48.3%


Goya/Pepsi 3rd burn Heet (Yellow) 24.5 16 41.5 212 199.9 44.9%


Goya/Pepsi Boil( steam) Heet (Yellow) 26.4 16 41.5 212 214.5 45.5%



Cat Initial Heet (Yellow) 12.1 16 39.1 212 137.3 56.8%

Cat 2nd burn Heet (Yellow) 21.3 16 39.1 212 190 49.6%

Cat 3rd burn Heet (Yellow) 24.8 16 39.1 212 210 56.1%


Double Cat Initial Heet (Yellow) 12.1 16 39.1 212 135.2 55.6%

Double Cat Initial Heet (Yellow) 12.1 16 39.1 212 93.9 31.7%
W/screen


Does this prove that one type of stove is better than another? Not at all! I like the Goya Stove system, after all I invented it  The Goya stove is a stove system that works pretty well for me. You can use the test setup and spreadsheet as a tool to test your favorite stove system and tweak it for maximum efficiency. Different types of alcohol fuels, pots, windscreens, height of stoves, etc., will have an effect on the test results. Test YOUR stove system and let us know what happens.

The numbers generated by the spreadsheet and the test burns will give you an idea of the amount of fuel that you need to carry, but they are not carved in stone!

A hiker should always carry an extra quantity of alcohol fuel to account for changing conditions and accidents, e.g.: spillage, changing temperature, etc.


Possible questions:

Q: Why use water?

A: its readily available everywhere.

Q: Does the water for the test have to be chilled?

A: No, use water at whatever temperature available. The spreadsheet uses whatever water temperature you enter for the calculations.

Q: What if my test water is frozen?

A: Find someplace warmer to camp. The spreadsheet does not provide for the melting of ice.

Q: Why did use only include information on 4 types of alcohols?

A: I could only find the information for these 4 types.
(Information on other types of alcohols would be appreciated.)

Q: Why include provisions to use Centigrade and milliliter (CC) values?

A: To keep the rest of the world happy.

Q: Why measure the alcohol fuel in milliliter (CC) values?

A: Much easier to measure than fractions of an ounce.

Q: Why are all but the input cells of the spreadsheet locked out?

A: I developed a significant headache putting together the spreadsheet, and I do not want the mathematically challenged to mess it up by changing the value(s) of a critical cell. If you want an unlocked copy of the spreadsheet, email me: atraildreamer@yahoo.com and I will forward to you an unprotected version of the spreadsheet.

Q: How will altitude changes affect my test?

A: I don’t plan on climbing a mountain to try this out; I’m going to do it in my kitchen, but if you need to adjust for altitude, see the chart at the bottom of the spreadsheet beginning at line 89.

Q: What about ambient air temperature?

A: What about it—I repeat, I am going to try this out in my kitchen.

Q: What about the starting temperature of the fuel?

A: I assume that it will be at room temperature, whatever that is, the fuel will get very hot when you light it up.

Q: Why do you have provision for 3 test burns?

A: As stated in the discussion of the test results, varying the amount of alcohol fuel caused a change in the efficiency of the stove system. Three tests will give the experimenter a better feel for the operation of a particular stove system and a close approximation of the amount of fuel that is needed to properly utilize a stove system.

Q: Can these tests be made more precise?

A: Sure…do you have a National Bureau of Standards laboratory that I can use for a while?

Q: Why did you come up with this method of testing stove efficiency?

A: To attempt to clear up a lot of confusion about the performance of various types of stove systems, and, possibly, to get a lot of people ticked off at me! 

Q: What should I avoid doing?

A: Burning down the homestead immediately comes to mind.

Q: What should I really avoid doing?

A: DO NOT USE GASOLINE!!!
http://www.woodgaz-stove.com/

Tony
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Location: Canberra Australia
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Re: Most efficient alcohol stove?

Post by Tony » Wed Oct 22, 2008 6:11 pm

The problem with using the efficiency equation is that it does not take into account the amount of fuel used only the amount of heating energy in the fuel and in my opinion gives a somewhat false sense of the true efficiency that is required by backpackers which is weight of fuel that has to be carried to boil the amount of water needed for a trip.

After a lot of research I decided to use this efficiency equation which is a used in the British Standards for testing cooking stove efficiency and it is used by many research institutions.

Eff=((MWS(TWE-TWE)Cw)+(MWS-MWE)He)/(MFS-MFE)Hf ( when I want to use it I set this equation up in Excel spread sheet)

Where
MWS=mass of water at start in kg
MWE=Mass of water at end in kg
Cw=Specific heat capacity of water J/kg.K , for water = 4.186kJ/kg.K
TWS= temperature of water at start ºC
TWE= temperature of water at end ºC
MFS= mass of fuel at start in kg
MFE= mass of fuel at end in kg
He= specific heat of evaporation water J/kg ,for water 2256 kJ/kg
Hf= heating value of fuel J/kg, Ethanol =26.8 MJ/kg, Methanol=19.7 MJ/kg, propane=46.3 MJ/kg, Butane=45.6 MJ/kg

example: if you do the above calculations (I am not going to type it all in) of boil 1l of water using 12 grams of propane fuel and then boil 1l using 28 grams of Methanol and allowing say 3 grams of evaporation you will get the same efficiency numbers of 30.6% out of the equation. In other words it does not take into account of the mass of fuel used, only the amount of energy in the fuel.

That is why I prefer to use a mass of fuel per unit of water per unit of temperature raised and in my preferred metric units it is grams of fuel used to raise 0.5liters of water 80ºC eg; 6g propane/80ºc/0.5l as per 14g methanol/80ºC/0.5l, I feel this give a far better representation of the true efficiency of a backpacking stove as the amount of fuel required to be carried.

MY2CW

Tony

oops56
Posts: 1920
Joined: Wed Sep 19, 2007 11:31 am

Re: Most efficient alcohol stove?

Post by oops56 » Wed Oct 22, 2008 7:47 pm

Tony wrote:The problem with using the efficiency equation is that it does not take into account the amount of fuel used only the amount of heating energy in the fuel and in my opinion gives a somewhat false sense of the true efficiency that is required by backpackers which is weight of fuel that has to be carried to boil the amount of water needed for a trip.

After a lot of research I decided to use this efficiency equation which is a used in the British Standards for testing cooking stove efficiency and it is used by many research institutions.

Eff=((MWS(TWE-TWE)Cw)+(MWS-MWE)He)/(MFS-MFE)Hf ( when I want to use it I set this equation up in Excel spread sheet)

Where
MWS=mass of water at start in kg
MWE=Mass of water at end in kg
Cw=Specific heat capacity of water J/kg.K , for water = 4.186kJ/kg.K
TWS= temperature of water at start ºC
TWE= temperature of water at end ºC
MFS= mass of fuel at start in kg
MFE= mass of fuel at end in kg
He= specific heat of evaporation water J/kg ,for water 2256 kJ/kg
Hf= heating value of fuel J/kg, Ethanol =26.8 MJ/kg, Methanol=19.7 MJ/kg, propane=46.3 MJ/kg, Butane=45.6 MJ/kg

example: if you do the above calculations (I am not going to type it all in) of boil 1l of water using 12 grams of propane fuel and then boil 1l using 28 grams of Methanol and allowing say 3 grams of evaporation you will get the same efficiency numbers of 30.6% out of the equation. In other words it does not take into account of the mass of fuel used, only the amount of energy in the fuel.

That is why I prefer to use a mass of fuel per unit of water per unit of temperature raised and in my preferred metric units it is grams of fuel used to raise 0.5liters of water 80ºC eg; 6g propane/80ºc/0.5l as per 14g methanol/80ºC/0.5l, I feel this give a far better representation of the true efficiency of a backpacking stove as the amount of fuel required to be carried.

MY2CW

Tony
Just do away with all them numbers stick your finger in the flame count see how hi you get before it hurts :lol:
Man play with fire man get burnt

Tony
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Location: Canberra Australia
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Re: Most efficient alcohol stove?

Post by Tony » Wed Oct 22, 2008 8:05 pm

Gidday Oops56,
Just do away with all them numbers stick your finger in the flame count see how hi you get before it hurts :lol:
Been there done that, I will stick to putting my fingers on a calculator. :) :)

I am forever burning the hair on my hands.

Pyrotechnic :twisted: :twisted: :twisted:

Tony

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zelph
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Joined: Tue Aug 14, 2007 1:53 pm

Re: Most efficient alcohol stove?

Post by zelph » Wed Oct 22, 2008 10:00 pm

Hi Tony, I like your method and will use it when full testing resumes. I still need to do a complete set-up of the electronics, raising and lowering mechanism etc. Need to finish cleaning the garage. :mrgreen:
http://www.woodgaz-stove.com/

irrationalsolutions
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Joined: Thu Sep 25, 2008 5:10 am
Location: South Carolina

Re: Most efficient alcohol stove?

Post by irrationalsolutions » Wed Oct 22, 2008 10:08 pm

i cant wait to have a garage again that way i can always put off cleaning it.
“Do or do not... there is NO try.” Yoda

Luke "Whats in (out) there?" Yoda "Only what you take with you."

Luke "I can’t believe it." Yoda "That is why you Fail.”

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zelph
Posts: 15834
Joined: Tue Aug 14, 2007 1:53 pm

Re: Most efficient alcohol stove?

Post by zelph » Wed Oct 22, 2008 10:14 pm

irrationalsolutions wrote:i cant wait to have a garage again that way i can always put off cleaning it.
:lol: :lol: I've gotten good at it :lol: :lol:
http://www.woodgaz-stove.com/

Tony
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Joined: Thu Sep 27, 2007 11:46 pm
Location: Canberra Australia
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Re: Most efficient alcohol stove?

Post by Tony » Wed Oct 22, 2008 11:01 pm

Hi Zelph,
Hi Tony, I like your method and will use it when full testing resumes. I still need to do a complete set-up of the electronics, raising and lowering mechanism etc. Need to finish cleaning the garage. :mrgreen:
I also have to clean up my garage and I have to do it this weekend as my daughter and some her fellow engineering students are coming over on Sunday to do their project in it, The project is making a bridge out of balsa wood, two pieces of 5mm square by 900mmm long and two pieces of 3mm square by 900mm long all 11 grams of it, the bridge will be tested to destruction. Apparently the record for this bridge design is 1200 N (120kg/265lb). She has purchased some extra Balsa wood and I have built them a testing machine.

We did a test on a prototype that she built last night but we only managed around 77.5kg or 760 N but we learned a lot.

I am finding this an interesting project.

balsa wood is very strong for its weight, I am thinking about making a SUUL balsa wood framed pack.

Tony

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zelph
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Re: Most efficient alcohol stove?

Post by zelph » Thu Oct 23, 2008 3:19 pm

Tony wrote:Hi Zelph,
Hi Tony, I like your method and will use it when full testing resumes. I still need to do a complete set-up of the electronics, raising and lowering mechanism etc. Need to finish cleaning the garage. :mrgreen:
I also have to clean up my garage and I have to do it this weekend as my daughter and some her fellow engineering students are coming over on Sunday to do their project in it, The project is making a bridge out of balsa wood, two pieces of 5mm square by 900mmm long and two pieces of 3mm square by 900mm long all 11 grams of it, the bridge will be tested to destruction. Apparently the record for this bridge design is 1200 N (120kg/265lb). She has purchased some extra Balsa wood and I have built them a testing machine.

We did a test on a prototype that she built last night but we only managed around 77.5kg or 760 N but we learned a lot.

I am finding this an interesting project.

balsa wood is very strong for its weight, I am thinking about making a SUUL balsa wood framed pack.

Tony
That record is quite impressive, gheesh, that's alot of weight!!!!! It sure would be nice if you showed us some photos of the bridges once they are complete before and after being demolished. You know, like a group shot of all of them :mrgreen:

The balsa backpack sounds like a great Daddy Daughter project ;) She'll love you more for it :D

See!!!! your daughter is an asset, a source of inspiration to get the garage tiddied up :lol:

My wife and daughters are a detriment, they keep adding stuff to the garage(on top of my stove making stuff) :lol: :lol:
http://www.woodgaz-stove.com/

Tony
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Joined: Thu Sep 27, 2007 11:46 pm
Location: Canberra Australia
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Re: Most efficient alcohol stove?

Post by Tony » Thu Oct 23, 2008 5:22 pm

Hi Zelph,
My wife and daughters are a detriment, they keep adding stuff to the garage(on top of my stove making stuff) :lol: :lol:
I know how you feel, my garage is full of old toys and superseded appliances from the house that are no longer needed but are not to be thrown out a just in case ( they will sit there for about 5-10 years and then get thrown out). I have no room to put more machines, stoves and gear, I need to put an extension my garage. :idea: :idea: :idea:

Image
Here is a picture of the latest balsa bridge that we tested, it is sitting on a quickly made up testing rig, I am using an old drill press with a cantilever arm 5:1 advantage with a spring balance that goes up to 23kg on the end which is puled by a motor driven winch for even pull, I record the measurement on the spring balance with a Digital video. I would like a high speed video camera but I do not have access to one anymore. I do not have pictures of the whole rig, I will post one soon. I will also post some pictures of the broken bridges.

The bridge has to span 180mm, it has to be no more than 70 mm wide and 100 mm high, the size of the block that will be pushing down on the top is 70 mm x 70 mm. The bridge will ultimately be tested on a tensile testing machine with a digital readout.

Tony

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