[Stoves] Stoves Digest, Vol 37, Issue 24

Mon Sep 23 11:28:26 CDT 2013

Hi Lanny,

There are two methods and metrics commonly used to measure the susceptibility of a stove from tipping over
1) method -- with a stove standing vertically, tilt the stove to one side until it falls over; metric -- the angle that the stove can be tilted away from vertical before it tips over on its own (typically used for portable stoves)
2) method -- apply a specified horizontal force to the stove; metric -- if the stove tilts, moves, deforms, or falls over when the force is applied (typically used for larger stationary stoves)

Protocols should not specify the required size of the base to prevent tipping. That decision is left to the designer based on his/her findings from the safety tests.

Most protocols do not require pots present on the stove. Yet, as you note, a pot can affect the stove's risk of tipping. No doubt all aspects of the cooking system--stove, user, pots/utensils, kitchen--affect cooking safety. Many people in the stove community tend to consider the larger contexts that influence the efficacy of technical designs. I have a similar viewpoint, and chose to include the stove when developing a new set of safety guidelines tailored to biomass cookstoves. You can find my work on stove safety here http://community.cleancookstoves.org/user_content/files/003/052/3052100/a8d66ebfa9745553fb1d971160a282d4-bssp1.0.pdf The text is copied from my Master's Thesis. Let me know if you want a copy of the full text.

Best regards,
Nate

--
Nathan Johnson
Assistant Professor
Department of Engineering & Computing Systems
Arizona State University

nathanjohnson at asu.edu<mailto:nathanjohnson at asu.edu>
480-727-5271

On Sep 21, 2013, at 11:00 AM, <stoves-request at lists.bioenergylists.org<mailto:stoves-request at lists.bioenergylists.org>>
 <stoves-request at lists.bioenergylists.org<mailto:stoves-request at lists.bioenergylists.org>> wrote:

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Today's Topics:

  1. Re: A doctoral thesis on stoves (Paul Anderson)
  2. Tip over hazard footprint and center of gravity. (Lanny Henson)
  3. Re: A doctoral thesis on stoves (Crispin Pemberton-Pigott)
  4. Re: A doctoral thesis on stoves (Lanny Henson)
  5. Re: A doctoral thesis on stoves (Lanny Henson)
  6. Re: Charcoal stove design (Lanny Henson)
  7. Re: A doctoral thesis on stoves (Richard Stanley)

----------------------------------------------------------------------

Message: 1
Date: Fri, 20 Sep 2013 14:00:55 -0500
From: Paul Anderson <psanders at ilstu.edu>
To: Discussion of biomass cooking stoves
<stoves at lists.bioenergylists.org>
Subject: Re: [Stoves] A doctoral thesis on stoves
Message-ID: <523C9B67.9010504 at ilstu.edu>
Content-Type: text/plain; charset="iso-8859-1"; Format="flowed"

Frank,

see below

Doc  /  Dr TLUD  /  Prof. Paul S. Anderson, PhD
Email:  psanders at ilstu.edu
Skype: paultlud      Phone: +1-309-452-7072
Website:  www.drtlud.com

On 9/20/2013 12:45 PM, Frank Shields wrote:

*Thanks Ron,*

**

*I was surprised to see snakes as being one of the problems listed on
page ten.  Wonder what kind?*

*I think snakes were added to give some issue that would have low threat
(10 being low and 1 is high).*

**

**

*Surprised to see twisted tape adding efficiency as I would think that
would just remove heat that was on its way to the pot.
*

They twisted tape (TT) is quite small and will be up to full temperature
quite quickly.   After that, they to not remove any more heat.   But the
added turbulence continues.   And seems to have substantial impact.

The test of the TT could easily be done in the Rocket stoves that have
been tested so many times.   Does 1 or more TT have impact there?

TT is one of several major designs for turbulence.   Looks like an
important topic for more study (and does not require fancy expensive
equipment.

**

**

*Now that all this info is available this would be a good place to
test different fuels, stoves etc. All of the 'six box' variables now
controlled and we can swap out one at a time to see what happens.
Re-arrange to report the following in order: *

**

*Review of the six variables:*

*1)**Fuel(s)*

*2)**Fuel manipulation between box1 and box 3*

*3)**Stove(s)*

                    3-A)  Stoves with fixed positions of the pot
supports in relation to the combustion zone.
                    3-B)   Stoves that have ease of changing the
distance between the combustion device and the pot supports, allowing
for "Manipulation between combustion device and the stove
structure).     Paul

**

*4)**Cooking utensil*

*5)**Manipulation between box 4 and box 6*

*6)**Task(s)*

*Calculations from Fuels > Tasks give the efficiencies. *

**

*Regards*

**

*Frank*

**

**

**

*Frank Shields*

*Control Laboratories; Inc.*

*42 Hangar Way*

*Watsonville, CA  95076*

*(831) 724-5422 tel*

*(831) 724-3188 fax*

*frank at biocharlab.com*

*www.controllabs.com*

**

**

**

**

**

**

**

*From:*Stoves [mailto:stoves-bounces at lists.bioenergylists.org] *On
Behalf Of *Ronal W. Larson
*Sent:* Thursday, September 19, 2013 10:43 AM
*To:* Discussion of biomass
*Subject:* [Stoves] A doctoral thesis on stoves

List:

   1,  I recommend this recent new (free) technical stove paper:

http://www.energsustainsoc.com/content/pdf/2192-0567-3-16.pdf

   2.  This is a shortened but still lengthy version of an Indian
doctoral thesis.  It concentrates on one village and one type of
stove, providing extensive testing and good reporting on especially
the amount of fuel consumed (mostly for water boiling) and the time
taken to acquire it.

   3.  The main new feature is on using a simple low cost means of
getting swirl and thereby better gas mixing.  The addition is called a
TT - twisted tape.  Seems like it is adding 5% to stove efficiencies
(which started in the 20-25% range), otherwise no changes to these
tradition stoves.  The paper provides a good review of almost
everything else about simple stoves, including comments on WBTs.   The
TTs should be applicable to Rockets, TLUDs, etc.

   4.  I have lost how I came to read it.  But think it came from
this site: https://www.engineeringforchange.org/news/categories/energy/

Ron

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Message: 2
Date: Fri, 20 Sep 2013 14:58:54 -0400
From: "Lanny Henson" <lannych at bellsouth.net>
To: "Discussion of biomass cooking stoves"
<stoves at lists.bioenergylists.org>
Subject: [Stoves] Tip over hazard footprint and center of gravity.
Message-ID: <E3F60BF4EDB64872A8016F710E6EC7EF at HP>
Content-Type: text/plain; charset="iso-8859-1"

Tip over hazard footprint and center of gravity.

I am working on a new stove design and I need the footprint to be large enough to not be a tip over hazard.

As I was testing a prototype I realized that not only the stove height should be considered, but the pot height and weight should be considered, because with a full pot the center of gravity is a lot higher than it is with just an empty stove.

Are there any guidelines or standards for tip over hazards considering the whole stove system, that is the stove with a full pot?

Lanny
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Message: 3
Date: Sat, 21 Sep 2013 03:57:38 +0700
From: "Crispin Pemberton-Pigott" <crispinpigott at gmail.com>
To: "'Discussion of biomass cooking stoves'"
<stoves at lists.bioenergylists.org>
Subject: Re: [Stoves] A doctoral thesis on stoves
Message-ID: <050001ceb644$0dab13f0$29013bd0$@gmail.com>
Content-Type: text/plain; charset="us-ascii"

Dear Paul

Before rushing to put in the TT's be aware that such devices in the actual
flame will impede combustion quite a bit, producing a lot of soot (clinging
to it).

If the carbon falls into the fire and burns, that might be OK. If, strictly
speaking, the purpose is turbulence, it could as well be created with
secondary air jets and the soot avoided. Everyone should try it to see the
effects.

Because we do not know the gas composition from the stove, it is hard to
know what the overall effect of the TTs was on combustion efficiency. This
is the sort of effect that is hard to guess.

Regards

Crispin

Frank,

see below

Surprised to see twisted tape adding efficiency as I would think that would
just remove heat that was on its way to the pot.

They twisted tape (TT) is quite small and will be up to full temperature
quite quickly.   After that, they to not remove any more heat.   But the
added turbulence continues.   And seems to have substantial impact.

The test of the TT could easily be done in the Rocket stoves that have been
tested so many times.   Does 1 or more TT have impact there?

TT is one of several major designs for turbulence.   Looks like an important
topic for more study (and does not require fancy expensive equipment.

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Message: 4
Date: Fri, 20 Sep 2013 17:26:13 -0400
From: "Lanny Henson" <lannych at bellsouth.net>
To: "Discussion of biomass cooking stoves"
<stoves at lists.bioenergylists.org>
Subject: Re: [Stoves] A doctoral thesis on stoves
Message-ID: <7007FA367BB346618B10FA8F4CE48928 at HP>
Content-Type: text/plain; charset="iso-8859-1"

I do not see how the twisted tape can create turbulence with the low velocities in the stove. There is probably something else going on that is increasing the efficiency. The TT may slow down the flow and reduce the excess air?

You may be able to send some smoke through the stove to see the flow path.

Also anything between the fire and the pot will block radiant heat.

 Dear Paul

 Before rushing to put in the TT's be aware that such devices in the actual flame will impede combustion quite a bit, producing a lot of soot (clinging to it).

 If the carbon falls into the fire and burns, that might be OK. If, strictly speaking, the purpose is turbulence, it could as well be created with secondary air jets and the soot avoided. Everyone should try it to see the effects.

 Because we do not know the gas composition from the stove, it is hard to know what the overall effect of the TTs was on combustion efficiency. This is the sort of effect that is hard to guess.

 Regards

 Crispin

 Frank,

 see below

   Surprised to see twisted tape adding efficiency as I would think that would just remove heat that was on its way to the pot.

 They twisted tape (TT) is quite small and will be up to full temperature quite quickly.   After that, they to not remove any more heat.   But the added turbulence continues.   And seems to have substantial impact.

 The test of the TT could easily be done in the Rocket stoves that have been tested so many times.   Does 1 or more TT have impact there?

 TT is one of several major designs for turbulence.   Looks like an important topic for more study (and does not require fancy expensive equipment.
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Message: 5
Date: Fri, 20 Sep 2013 18:00:31 -0400
From: "Lanny Henson" <lannych at bellsouth.net>
To: "Discussion of biomass cooking stoves"
<stoves at lists.bioenergylists.org>
Subject: Re: [Stoves] A doctoral thesis on stoves
Message-ID: <5EBA6465C9F04CB398F27F943A97ADD8 at HP>
Content-Type: text/plain; charset="iso-8859-1"

If the pot holders are too high, all the heat may flow to one side of the pot, especially if there is wind or air turbulence in the cook space

A smaller gap spreads the flow out across the bottom of the pot. The increased velocity also helps.

The problem is that with a multiple pot stove you have a cook top, and you don't want the heat flow to touch the cook top.

With a short potholders the heat scrapes the stove top.

You are trying to cook the pot not the stove. I learned this using a rectangular cook top which wants to warp when heated.

With the School Lunch Cooker I let the burner extend 1"/25mm above the cook top and used 2"/50mm tall pot holders. This puts the heat on the pot and shields the stove top with a layer of dead air.

 ----- Original Message -----
 From: Sarbagya R. Tuladhar
 To: Discussion of biomass cooking stoves
 Sent: Friday, September 20, 2013 4:16 AM
 Subject: Re: [Stoves] A doctoral thesis on stoves

 12-15 m high ???

 Cheers

 Sarbagya

 On 20/09/2013, at 4:35 AM, Crispin Pemberton-Pigott wrote:

   Very good paper with some novel adaptions of the test methods, approaches to the community and the retrofitted device.

   The money photo is this one:

   <image003.jpg>

   The pot rests are far too tall and create several simultaneous problems for effective heat transfer. The addition of turbulators is one way to address some of this error.

   Given the reported power level the pot rests should be about 12-15m high and that would reduce the initial problem. It would be interesting to see a stove built with both changes.

   Regards
   Crispin

   +++++++++++
   List:

       1,  I recommend this recent new (free) technical stove paper:

        http://www.energsustainsoc.com/content/pdf/2192-0567-3-16.pdf
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Message: 6
Date: Fri, 20 Sep 2013 18:30:29 -0400
From: "Lanny Henson" <lannych at bellsouth.net>
To: "Discussion of biomass cooking stoves"
<stoves at lists.bioenergylists.org>
Subject: Re: [Stoves] Charcoal stove design
Message-ID: <26DA5615FBD74C88B50C5623E8345321 at HP>
Content-Type: text/plain; charset="iso-8859-1"

I see they are using a wire charcoal grate, and you need to remove pot to add fuel.

The riser section that holds the pot, restricts the "radiant view", and it is not recommended to use the stove in the rain.

 ----- Original Message -----
 From: Alex English
 To: Discussion of biomass cooking stoves
 Sent: Wednesday, September 18, 2013 9:55 PM
 Subject: Re: [Stoves] Charcoal stove design

 AT ETHOS a few years back (2010 I think), Bryan Wilson gave an excellent presentation on an improved combustion charcoal stove. The ETHOS website doesn't seem to have a link for it.
 I believe this is the the one,
 http://www.envirofit.org/products/?sub=cookstoves&pid=12

 Alex

 On 18/09/2013 5:37 AM, Saastamoinen Jaakko wrote:

   Dear Frank and Crispin,

   the main DIRECT product in the reaction of carbon with oxygen is CO but also some CO2 is directly formed. CO that is formed can be oxidized to CO2 (CO+?O2=CO2) at high enough temperatures in the vicinity of carbon particle or in later stage in the gas flow. So there are different zones along the gas flow in carbon particle layer when air (or gas) is flowing upwards through it:

I)                    Zone where exothermic reaction C+?O2=CO takes place (but some CO2 is also formed). Here the gas temperature is rather low because it is close to the inlet and the gas has not heated up enough. So CO is not burning well.

II)                  Zone where the gas temperature becomes high enough so that also the exothermic reaction CO+?O2 =CO2 (enhanced by H2O) takes place in the gas. This leads to even higher local temperature along the gas flow so that exothermic reactions (C+?O2=CO and CO+?O2=CO2) take place at even higher rate. Here also the endothermic reaction CO2+C=2CO takes place because the char temperature is high enough. This rrwaction adjust the temperature level preventing it to increase very high. Then at the location, where all oxygen is consumed, the gas temperature and CO2 concentration reach the maximum values.

III)                After that the carbon reacts with CO2 producing carbon monoxide in endothermic gasification reaction CO2+C=2CO. The gas is cooled due to this endothermic reaction. If the layer is very thick, the gas is cooled to a temperature at which the reaction rate C+CO2=2CO becomes very low.

   So some conclusions:

1.       For a thin layer, there is only zone I producing CO.

2.       For thicker layer (zone II), the exit gas contains much CO2 and some CO. The exit gas is hot and CO may be burned introducing (preheated) secondary air. The exit gas is hottest if the thickness of the layer is just in the  intermediate transfer regime from zone II to III.

3.       For a thick layer, the gas contains much CO and some CO2. Its temperature is low and it is difficult to burn CO without highly preheated secondary air.

   The reaction CO+?O2=CO2 can take place also in the other direction. This reverse reaction (dissociation) of carbon dioxide is not significant at temperatures <1800 K.

   Regards

   Jaakko

   From: Stoves [mailto:stoves-bounces at lists.bioenergylists.org] On Behalf Of Frank Shields
   Sent: 18. syyskuuta 2013 0:55
   To: 'Discussion of biomass cooking stoves'
   Subject: Re: [Stoves] Charcoal stove design

   Dear Crispin,

   So the CO2 > CO is endothermic. But still needs carbon. As I see it the only difference is the temperature changing as the gases move around the pot. Wondering if the reading could be affected by temperature? Perhaps amount of gas entering the instrument or something? Interesting. Could hydrogen react with one of the oxygen in CO2 making water leaving CO?

   Frank

   From: Stoves [mailto:stoves-bounces at lists.bioenergylists.org] On Behalf Of Crispin Pemberton-Pigott
   Sent: Tuesday, September 17, 2013 2:01 PM
   To: 'Discussion of biomass cooking stoves'
   Subject: Re: [Stoves] Charcoal stove design

   My conclusion is the CO splits endothermically. It does not happen in stoves with high EA.

   Crispin

   Dear Crispin,

   <snip>

   I found that directly above the middle of a good stove (under the pot) there is zero CO - I was amazed. But nearer the edges there is more.

   [Frank >] How is that possible? I thought going from CO2 > CO could only occur be in a bed of char. This is very strange.

   Regards

   Frank

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Message: 7
Date: Fri, 20 Sep 2013 15:40:47 -0700
From: Richard Stanley <rstanley at legacyfound.org>
To: Discussion of biomass cooking stoves
<stoves at lists.bioenergylists.org>
Subject: Re: [Stoves] A doctoral thesis on stoves
Message-ID: <FF1ACBF6-516D-489B-A47F-34F289940E2F at legacyfound.org>
Content-Type: text/plain; charset="windows-1252"

fyi,
These twisted straps look very much like a water diffuser vanes on the impulse pump of a one Victor Schauberger     http://schauberger.co.uk/home.html
but that is as far off topic as can be..
Richard
On Sep 20, 2013, at 1:57 PM, Crispin Pemberton-Pigott wrote:

Dear Paul

Before rushing to put in the TT?s be aware that such devices in the actual flame will impede combustion quite a bit, producing a lot of soot (clinging to it).

If the carbon falls into the fire and burns, that might be OK. If, strictly speaking, the purpose is turbulence, it could as well be created with secondary air jets and the soot avoided. Everyone should try it to see the effects.

Because we do not know the gas composition from the stove, it is hard to know what the overall effect of the TTs was on combustion efficiency. This is the sort of effect that is hard to guess.

Regards
Crispin

Frank,

see below

Surprised to see twisted tape adding efficiency as I would think that would just remove heat that was on its way to the pot.
They twisted tape (TT) is quite small and will be up to full temperature quite quickly.   After that, they to not remove any more heat.   But the added turbulence continues.   And seems to have substantial impact.

The test of the TT could easily be done in the Rocket stoves that have been tested so many times.   Does 1 or more TT have impact there?

TT is one of several major designs for turbulence.   Looks like an important topic for more study (and does not require fancy expensive equipment.

_______________________________________________
Stoves mailing list

to Send a Message to the list, use the email address
stoves at lists.bioenergylists.org

to UNSUBSCRIBE or Change your List Settings use the web page
http://lists.bioenergylists.org/mailman/listinfo/stoves_lists.bioenergylists.org

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