TLUD Bread Oven

TLUD Bread Oven
Flat Bread
TLUD Parts
TLUD Assembled
Oven Temp Profile

Estremera Nova, Bunyola, Illes Balears, Spain htttp://www.cuinessolars.jimdo.com

Marc Ayats Plana has been working on TLUD stoves and improved low thermal mass ovens. This TLUD powered low thermal mass oven was inspired by the Anderson's Recho Rocket Oven, and uses a Champion style TLUD heating stove to power the low thermal mass earth oven.

For Marc's excellent writ-up download the pdf TLUD-OVEN Description
These are some quick notes:

He has made some changes to the TLUD style oven

  • Increased primary air draft, which can apport enough oxigen to burn the charcoal generated during the gasification process and continue giving heat to the oven. Now the primary air enters around the lower perimeter of the reactor, instead of having a single inlet tube like in the original model.
  • Increased the length of the riser, which also sustains the diffuser. This extra extension allows the complete combustion of gases gasification to completely remove the visible smoke in the oven.
  • TLUD Reactor. Diameter: 20cm. Total length: 30cm. Fuel Height: 20cm
  • TLUD Outskirt. Diameter: 22cm. Diameter central hole: 10cm. Total length: 25cm
  • TLUD Riser and diffuser. Diameter: 12 cm. Total length: 30cm. Diffuser: granite piece 2cm thick and 15cm diameter
  • Fuel load: 3.38Kg pellets

The Low Thermal Mass oven is based on the Haiti Rocket oven http://www.rechoroket.com
To see more pictures of the TLUD oven and the process of construction go to:
http://cuinessolars.jimdo.com/forns/

In the Oven Temperature graph, you can see the complete temperature profile. Marc did a side by side comparison of both a 20cm reactor TLUD and a smaller TLUD, with 12,5cm reactor.
"Note: the temperatures refers to the inside side of the wall oven, half way between the baking surface and the top hole. Note2: the temperatures were taken by a temperature datalogger and a type K probe."

Marc's Notes and TLUD size comparison are copied here:
Notes about 20cm TLUD test

  • 8 minutes to get 200 ° C
  • 17 minutes to get 250 ° C
  • 1h17minutes to peak at maximum temperature: 298ºC
  • In 1h30m from start the flames extinguished and began the char gasification
  • In 2h30min from start the temperature dropped definitely below 200 º C
  • It has been spent a total of 3.38 kg of fuel. The price of 15kg of pellets is 6 € approx. Therefore, the price of this oven batch was 1.35 €.
  • On average, consumption was 22.5 g of fuel per minute.
  • No visible smoke appeared at any moment of the process.
  • The outside temperature was 32 º C
  • Just for testing, 2 loaves of bread were cooked with a total weight of about 1 kg, occupying a total of about 35 minutes. In total, I could have baked around 5kg of bread in the 2.5 hours of operation.
  • The bread was cooked optimally. Although, maybe the temperature was a little higher than the desired one in most bread recipes (in general, we can say that bread needs a temperature of 250ºC the first 5-10 minutes but then lows to 180- 200ºC for the rest of the baking process)
  • A lot of heat went out of the upper hole of the oven. Maybe this tends to cool the oven.

Comparison between different TLUD sizes

  • The power of the TLUD is proportional to the area of the reactor. So, in theory, the 20cm diameter TLUD (314cm2) should give us 256% more power than the 12,5cm diameter one (122,7cm2).
  • The experimental results are more or less confirming the theory, as the average temperature and the maximum temperature are about 220% of that of the 12,5cm one.

Table of Experimental Results:

Parameter Ud TLUD 12.5cm TLUD 20cm
Radius cm 6.25 10
Radius Squared cm2 39.06 100
Area cm2 122.7 314.2
% 100.0% 256.0%
Average temperature °C 125 275
% 100.0% 220.0%
Maximum temperature °C 133.31 298
% 100.0% 223.9%

It looks like a TLUD gasifier of the right size can power a low mass oven. Marc notes that more study is needed, but the right combination of oven and TLUD could make an energy efficient clean baking oven for family and/or community use.

References

AttachmentSize
TLUD Oven Description and Notes2.49 MB