The Magazine Stove- A Better(?) Stove. Dale Andreatta, Ph.D., P.E. Mechanical Engineer, S-E-A Ltd. Adjunct Professor, The Ohio State University

Transcription

1 The Magazine Stove- A Better(?) Stove Dale Andreatta, Ph.D., P.E. Mechanical Engineer, S-E-A Ltd. Adjunct Professor, The Ohio State University

2 What is important in a stove? Low fuel use. Low pollution. Works with local cooking habits and foods. Low cost. Durable. Adequately powerful. Safe (hard to tip, no sharp edges, etc.). Easy to use. Attractive.

3 What makes a stove easy to use? Easy to light. You can see the fire. Infrequent fire-tending required. Easy fire-tending. Easy to rekindle if necessary. Not much fuel processing needed. Can burn variety of fuels, large, small, straight, branched, wet, dry, etc. Not affected by wind.

4 Assessment of 2 cooking methods Attribute Rocket Stove Open Fire Easy to light Yes Yes, if you know the tricks You can see the fire No Yes Easy to tend the fire Yes No Easy to rekindle the fire if necessary. Use wide variety of fuel shapes and sizes Sometimes?????? Moderately Yes Resistant to wind Yes No

5 Problems with Rocket Fuel door size is small, 12 cm wide by 6.5 cm tall (Most stove doors are larger, some smaller). Can t see the fire easily. Limited shapes and sizes of fuel can be handled. Fire box is small, fuel-tending is easy, but frequently needed.

6 Branched Wood

7 Branched Wood

8 Big Wood

9 Big Wood

10 The Rocket Stove with a Fuel Magazine- The Magazine Stove Magazine meaning a place where combustible material is stored. Keep the good features of a rocket stove, but extend the firebox. Fuel in the firebox burns slowly, giving a longlasting fire. Hopefully reduce the number of times the user needs to tend the stove. Also, slope the grate so you can see into the stove. Also, expand the fuel opening to burn larger or branched wood.

11 Magazine Stove

12 Magazine Stove

13 Section view looking down

14 Sloped Grate Downward sloped grate makes it easier to see into the stove and see the fire and wood. Slope of grate has a large effect on burning rate. Current slope, about 20 degrees is about right for natural wood, but dry wood (cut lumber) burns too fast.

15 Burn Time for Wood Samples Average Burn Time 35 Seconds Average Burn Time 52 Seconds

16 Test 1-Count How Often You Have to Tend the Fire Modified water boiling tests were done with a Stove Tec (insulated ceramic) rocket stove and magazine stove. Two tests each on cut lumber and natural wood. Measure fuel use, efficiency, time to boil, and number of times to tend fire in both high power and 45-minute simmering phases.

17 Cut lumber Small and large pieces About 8% moisture Always straight

18 Natural wood, maple and crabapple Dried indoors or under cover, moisture content about 12.5%. Straight and branched. Large and small pieces.

19 Test site

20 Rocky the Lab Assistant

21 Tests

22 Modified water boiling test details and calculated results A lid is used because most people use a lid. During the simmering phase the water is kept at least simmering, because that s what people would do. No separate hot start. Measure the weight of the fuel tray before the test, at boiling, and after the test. Use these weights for fuel use data. Also estimate the unburned wood and unburned charcoal in the stove at boiling and end of test. Use these numbers with the weight of the fuel tray to calculate the actual heat released and the heat transfer efficiency. Starting weight of water is 5000 g +/- 50. Starting temperature around 20 C. Correct all high power results (time to boil and fuel used during high power) to reflect a test where the mass is exactly 5000 g and the temperature rise is 80 C. Keep large and small pieces of wood in the wood tray. Use any type of fuel you want, but use the same fuel for all stoves. Assume the energy content of wood is 16,000 J/g no matter what the moisture content. Assume the energy content of charcoal is 30,000 J/g. Since the purpose of this test was to see how the stoves performed with less-than-optimal tending, follow strict rules about tending the fire. During the high power phase, if there was fire coming out the top of the stove 50% of the time, let it be. If there was not, shove in a lot of wood so as to maximize the time before the next fuel tending. In the simmering phase, if simmering, let it be. If it stops simmering, shove in a lot of wood so as to maximize the time before the next fuel tending. Exception: if the simmering phase is within 10 minutes or so of being finished, shove in the amount of wood you need to finish the test. I believe this is more like how the stove would actually be operated by the users, unless they were a roadside food vender who was present at the stove constantly, or some similar situation.

23 Results, cut lumber, average of 2 tests Item Stove Tec Magazine Stove Fuel tending occasions, high power 2 2 Fuel tending occasions, simmering 2 2 Total fuel tending occasions 4 4 Fuel used, high power (grams) Fuel used, simmering (grams) Total fuel used (grams) Overall heat transfer efficiency Time to boil (minutes)

24 Results, natural wood, average of 2 tests Item Stove Tec Magazine Stove Tending fuel occasions, high power Tending fuel occasions, simmering Total tending fuel occasions Fuel used, high power (grams) Fuel used, simmering (grams) Total fuel used (grams) Overall heat transfer efficiency Time to boil

25 Test 2-Walkaway Water Boiling Test Similar to previous modified water boiling test, but After fire is started, walk away for 10 minutes at a time. After boil, walk away for 15 minutes at a time.

26 Modified water boiling test details (Walkaway test) and calculated results A lid is used because most people use a lid. During the simmering phase the water is kept at least simmering, because that s what people would do. No separate hot start. Measure the weight of the fuel tray before the test, at boiling, and after the test. Use these weights for fuel use data. Also estimate the unburned wood and unburned charcoal in the stove at boiling and end of test. Use these numbers with the weight of the fuel tray to calculate the actual heat released and the heat transfer efficiency. Starting weight of water is 5000 g +/- 50. Starting temperature around 20 C. Correct all high power results (time to boil and fuel used during high power) to reflect a test where the mass is exactly 5000 g and the temperature rise is 80 C. Keep large and small pieces of wood in the wood tray. Use any type of fuel you want, but use the same fuel for all stoves. Assume the energy content of wood is 16,000 J/g no matter what the moisture content. Assume the energy content of charcoal is 30,000 J/g. Since the purpose of this test was to see how the stoves performed with less-than-optimal tending, follow strict rules about tending the fire. During the high power phase, once the fire is running well load it with fuel and don t tend the fire for 10 minutes. You don t need to actually walk away. After 10 minutes, tend the fire as you see fit. After boiling starts, increase the time span to 15 minutes. The 10 or 15-minute time interval starts when you finish tending the fire. After boiling starts, the next fire tending will be 15 minutes after the previous. In other words, the time interval that includes the start of boiling will always be 15 minutes long.

27 Different (1-door) Stove Tec Stove Tested

28 Modified Magazine Stove-More Optimized Heat Transfer Path

29 More Optimized Magazine Stove Magazine stove used the top part of a Stove Tec stove, which has a gas flow path more optimized for better heat transfer. In actual use, the magazine stove would be fully optimized and have better efficiency than the crude prototype tested here.

30 Results Stove Stove Tec Magazine Stove Time to Boil (min) Fuel Used (g) high power Fuel Used (g) low power Total Fuel Used (g) Overall Efficiency

31 Summary Ease of use is an important stove attribute. Rocket stove has many good features, and is fairly easy to use, but it could be improved further. Rocket stove with fuel magazine is a possible improvement.

32 Current Version of Magazine Stove Less frequent fuel tending. Can see fire. Larger fire box and fuel door allows larger and branched fuels. Sometimes, the fuel use is high, but this can probably be improved.