[Stoves] TLUD-Oven!

Sat Jul 26 10:42:57 CDT 2014

Hi Crispin se this idea for street vendors I have made this to be use with TLUD stoves

Best regard

Gus

Enviado desde mi Samsung Mobile de Claro

<div>-------- Mensaje original --------</div><div>De: Crispin Pemberton-Pigott <crispinpigott at outlook.com> </div><div>Fecha:26/07/2014  03:15 AM  (GMT-06:00) </div><div>A: stoves at lists.bioenergylists.org </div><div>Asunto: Re: [Stoves] TLUD-Oven! </div><div>
</div>Dear Marc

Thanks for sharing the comprehensive report and providing many relevant numbers. The duration of the burn certainly seems adequate for most baking. 

Your comment on heat loss is very relevant. I caution that you cannot tell how much heat is being lost without gas measurements. You might do something that results in a lower exit temperature but an increase in CO (chemical loss) or higher dilution by excess air (mechanical loss). You have reached the point where further development needs a combustion analyser. 

If you research the Siegert Formula you will find the appropriate tool for the next stage of development of the burner and oven structure. You need three fuel-specific constants, the temperature, the CO and either the O2 or CO2 concentrations in the exit gases to make the calculation (which gives the total heat loss).

Controlling the primary air flow will control the oven temperature. Adjusting the secondary air flow will optimise the combustion and simultaneously limit heat losses by minimising excess air. 

Bread baking is slightly endothermic. You must also heat the mass of wheat to 94 degrees minimum (in the centre) and evaporate some of the moisture. It takes about 3 kw for 1 hour to bake 16 loaves of 800 g each. That is the performance of a well insulated electric oven. That provides a comparison of what energy is need for the actual baking. 

There is a rule-of-thumb for gas ovens (which you have) which is something like 1/3 the electrical efficiency. Maybe Andrew Heggie remembers it. It means it is possible to bake 16 x 800 g loaves with 9 kWh of heat. ‎12.8/9= 1.5 kg of product per kilowatt-hour. 

If the fuel was 15 MJ/kg it would take 2.5 kg to bake the 16 loaves (including preheating) at 180 C.

As you limit the losses, the smaller reactor might turn out to be adequate for your needs.

The above baking information and numbers are based in a real 220 v, 3 kW electric oven and a modelling spreadsheet predicting the time needed to bring the dough above 93 degrees at which point it becomes bread. 

The model predicted 53 minutes and the oven took 55 so the process are reasonably well understood. Bakeries normally test the centre of the loaf ensuring it is 94 C or a little higher. 

Regards 
Crispin
From: Marquitusus
Sent: Saturday, July 26, 2014 02:46
To: stoves at lists.bioenergylists.org
Reply To: Discussion of biomass cooking stoves
Subject: [Stoves] TLUD-Oven!

Hi,

I'm very glad to send to inform about my last work, the TLUD-OVEN. I wanted to put together the wonderful light thermal mass ovens from Recho Rocket with the very clean TLUD technology, and that's it! 
The results are very promising: no smoke at all, no soot, very fast heating and very comfortable cooking, as you can leave the fire unattended for about 2h30min, and concentrate on cooking!

I think it can be a really interesting device that can allow very clean and efficient baking.
I send the link to the stoves bioenergylists where I posted the file with the details: http://stoves.bioenergylists.org/content/tlud-bread-oven
I also attach the temperature profile graph and the full pdf paper with all the details.

Just comment what you think!

Marc
www.cuinessolars.jimdo.com

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