[Stoves] FW: Tlud stove testing

Tue Dec 16 03:37:54 CST 2014

Respected sir,
          The size of coconut shell pieces that I used for testing is about
2 cm* 3  cm.
On Dec 16, 2014 3:02 PM, "Marquitusus" <marquitusus at hotmail.com> wrote:

> Hi Saloop, can you tell us which is the particle size and shape of your
> coconut shells fuel?
> It would be very useful for me, in oder to compare your design with mine,
> which uses almond husks,
>
> Thanks,
> Marc
>
> ------------------------------
> From: crispinpigott at outlook.com
> To: stoves at lists.bioenergylists.org
> Date: Mon, 15 Dec 2014 13:30:00 -0500
> Subject: Re: [Stoves] FW: Tlud stove testing
>
> Dear Saloop
>
>
>
> I had a look at the stove and the calculations.
>
>
>
> Please note that the formula for efficiency (which is widely used in that
> same format) does not give the correct answer for the numerator – the heat
> gained by the pot.
>
>
>
> The water cooled during the last 10 minutes and the lost energy was
> converted into evaporated water. The correct number of Joules gained by the
> pot is:
>
> (I am using grams of water, °C and Joules)
>
>
>
> Final mass of water x ΔT1 x 4.186
>
> Plus
>
> Missing mass of water x ΔT2 x 4.186
>
> Plus
>
> Missing mass of water x 2257
>
>
>
> Where ΔT1 = initial and *final* temperature (not boiling!)
>
> And
>
> Where ΔT2 = initial and boiling temperature
>
>
>
> This is a common mistake so don’t be unduly alarmed. The formula you are
> using only works if the final water temperature is still at the boiling
> point. The formula in the paper double-counts the number of Joules lost
> cooling from boiling to final temp. This error is covered in the paper *KEY
> DIFFERENCES OF PERFORMANCE TEST PROTOCOLS FOR HOUSEHOLD BIOMASS COOKSTOVES*,
> Zhang, Y. et al 2014 at DOI:10.1109/DUE.2014.6827753
>
>
>
> The error is included in several national test methods. Whenever you see
> that a test method has as an ‘ending point’ the water at a temperature
> below the boiling point, you should be suspicious that there is a
> calculation error in the heat gained by the pot caused by double counting.
> Your real efficiency number is lower than you suspect.
>
>
>
> Regarding the design:
>
>
>
> I see your note about the secondary air holes being 40mm below the
> concentrator ring. This is a good idea. If you bring them down to the top
> of the fuel it will burn better for two reasons: there is more heat
> available at the fuel surface which promotes faster lighting and a higher
> flame temperature throughout the burn. Further, there is more vertical
> height for the flame to finish burning before the gases hit the pot. At the
> moment it looks about right (40mm + 85mm riser).
>
>
>
> The secondary air holes are probably too many and too small. The flames
> that shoot in around the secondary air have to reach the centre in order to
> get a clean burn before the flames hit the pot. I suggest enlarging every
> other one of the lower holes to 10mm and leave the ones in between at 8mm.
> Then close all the top holes with a strip of metal round the chamber.
>
>
>
> This will leave all the lower holes open (nearest the fuel) and a reduced
> total secondary air supply. It may still be too much. It will be difficult
> to tune it exactly without an oxygen measurement. You would want to have an
> O2 concentration in the exhaust of about 9-11%.
>
>
>
> If you can get a combustion analyser and measure the gases as they emerge
> from between the pot and the stove, making sure not to allow any dilution
> by the air near the sample point, you can reduce the number of holes until
> your get the correct O2 level at high power. When it is correct, the heat
> transfer efficiency will rise considerably. My guess is that at the moment
> your O2 level in the exhaust gases is at least 15-17%.
>
>
>
> Once you have that corrected, you want to get the CO as low as possible by
> ensuring the air shooting through the secondary holes reaches the centre.
> With 10mm you should be OK. 8mm is too small for the air to reach the
> centre of a 165mm diameter fuel chamber unless the material around the hole
> is shaped like a nozzle.  It is easy to close holes while running by
> popping an 8mm bolt into a few holes. Spread them around. This is normally
> done with an O2 meter running so you can watch the excess air (EA) level.
>
>
>
> What you want is to have enough inertia imparted into the secondary air so
> it is carries into the centre of the combustion zone. That is accomplished
> by converting the force of the draft (calculated from the riser height and
> average temperature) into velocity. There is work being done so the energy
> to do that is limited by the draft. The energy comes from the available
> ‘chimney draft’ which is a form of fan, really. When everything is correct,
> the flame will completely cover the fuel bed and the exhaust O2 will be
> 9-11%. It is that combination which leads to a high efficiency, clean burn.
> O2 can drop to 7% but you are running up against limits there to do with
> mixing. I would accept 8% at highest power and 10% at other settings.
>
>
>
> You probably have far more primary air than is needed. You could just make
> fewer holes. If you make too few, the power will be reduced (lower burn
> rate).
>
>
>
> When you are making a star pattern of holes like that, rotate each set of
> holes 30 degrees to sit midway between the previous set. The reason is to
> spread the heat of combustion out more. As you have it now, the ‘lands’
> (the metal between the holes) will deteriorate rapidly from overheating.
>
>
>
> The surface temperatures are probably not a major loss from the stove – it
> is the excess air that is killing your efficiency. Getting it correct
> should give you a ≈1.5x  increase in heat transferred, i.e. into the high
> 20’s even if you are making charcoal.
>
>
>
> Re the big hole in the square shell (at the top). Cut it 16mm smaller than
> the shell that goes into it, and hammer it outwards  to create a vertical
> lip. With a bit of care you can get a really good fit between the riser and
> the body. That limits air flow through the gap and increases the preheating
> of the secondary air. If you can, locate a steep pipe that has the right
> inside diameter to suit the hole size you need. Then you can hammer the
> material over 90 degrees using the steel pipe as a collar, banging on the
> inside. In the end you will have a rigid, round hole in the top of the
> body. The lip can go upwards or downwards as you prefer.
>
>
>
> Later you can spot-weld the riser onto the lip.
>
>
>
> Regards
>
> Crispin
>
>
>
>
>
> *From:* Stoves [mailto:stoves-bounces at lists.bioenergylists.org]
> *Sent:* Monday, December 15, 2014 12:08 PM
> *To:* 'Discussion of biomass cooking stoves'
> *Subject:* [Stoves] FW: Tlud stove testing
>
>
>
> The file with the tests results for this stoves was too large to send
> through the list, so I posted it here:
>
> http://stoves.bioenergylists.org/content/metal-chulah-stove
>
>
>
> Kind regards,
>
> Erin Rasmussen
>
> Stoves List Administrator
>
> erin at trmiles.com
>
>
>
> *From:* Saloop T S [mailto:t.s.saloop at gmail.com <t.s.saloop at gmail.com>]
> *Sent:* Monday, December 15, 2014 3:34 AM
> *To:* Discussion of biomass cooking stoves
> *Subject:* Tlud stove testing
>
>
> Respected Sir's,
>               I am a student from Kerala, India doing project on a tlud
> gasifier stove. I have made two 2 models of stove based on Dr. Paul
> Anderson and others work. In my second model I have tried to add a riser
> and concentrator disc arrangement so that I thought it may increase the
> efficiency of the stove. I have done two tests on it 1) with out the riser+
> concentrator disc- test I and 2) with riser and concentrator disc to find
> WBT efficiency of test one to be 21.7 and test two to be 21%.
> I would like to know whether the addition of riser+ concentrator disc will
> increase the efficiency of a stove. Is that anything that wrong with my
> experiment?. I would like you to comment on it and help me.
> I have attached a detailed report on my experiments and my model herewith.
> Thanking you,
>
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