23 January, 2015

Building a wood-optimal, safe, efficient and easy firewood: Continuation

Example stove with vermiculite plates and air intake to improve combustion
I keep turning the issue of simple and efficient stove burning (low CO2), my goal before automate with Arduino and complicate thing is to seek simplicity.
Everything should be made ​​as simple as possible, but not simpler. Albert Einstein
First of all I will discuss a couple of important things in any boiler or fireplace:
  • Pressure of fumes (sub-Atmospheric): It depends on the height of the chimney, caudal (diameter) and flue gas temperature rising by it; more value for any of these three variables shot improvement. If too much heat recovered from combustion, the fireplace is narrow and low rise in output has no anti-wind cap, going to have problems in your smoke fire under; the combustion chamber will be filled with smoke and even put a door will not improve much the problem and the fire may drown in their own CO2. It is important a good shot if you do not want to fill with smoke every time you load wood burning stove.
  • The flue gas temperature is not the same newly lit already running at full speed, so if the opponent much heat from the smoke at all times, it will cost you is fully operational; will require going very slowly with fine firewood easily combustible until heated throughout and chimney depression get enough natural draft heat of the fumes, and pull more energy. This problem is avoided by placing a mechanism to shorten the path of the smoke during preheating the oven, or designing it so that at no time was too cool smoke (but lose performance).
For a great performance without smoke fill must think of a progressive system of heat recovery, that the higher temperature fumes (or gases from combustion, whatever you want to call it), remove more heat from these (regulating the shot input and output) and at home (the center of combustion) the highest temperature occurs with more oxygen ell possible (and operate the pellet with yields> 90%).
But regulate automatically without gadgets is another story ...

The idea on my mind is a simple recirculation, as shown in the following scheme where the stove cut in half (apologies because I've drawn in 5 minutes):

The top can be higher to accumulate more hot air, but I simplified to stay paperless;)
You see intend to be modular; a base with the ash made of angular steel drawer ash veneer (optional wheels) and above the fireplace, to the waist, made of brick and refractory cement box.

In the scheme can be seen as the heat of the flames affect the smoke deflector so that we take that heat to preheat the air to be injected over the flames (improving combustion) , in addition to redirect the flames forward heat have less travel, and we took him to a chamber (the higher the better) where warmer air from accumulating on top (staying longer in the circuit), heating bricks or sheet that area, and where you will extract with a fan or an efficient heat sink to be automatically activated with a thermostat (about 60).
To clean the elbow that makes before leaving the chimney gases we will put a record in the front or back (if we put wheels).

On the other hand would have two air inlets ; through the slot in the ashes, which come regulated by the drawer (I think 25% to stoke the embers is sufficient), and the remainder injected into the top of the fire with preheated air to improve combustion at the best remix fumes with flames and more oxygen than traditional stoves (whose air intake is only for the coals, they consume most of the oxygen).

It can be difficult to build refractory to someone who is not very skilled brick, but with a little patience could be done; need to simplify the design as possible.

I want something simple, cheap to build and performance, and by not carrying water systems (for now) has no danger, and that it can be done either to replace a low heat and conserve fuel and labor.

Vermiculite boards are increasingly used in stoves; It is a light, clean, easy to work and enduring high temperatures, so you avoid the problem of weight and deformation of plates traditional stoves.
It remains for me to define the structure; how it will be mounted, how we got hold the bricks in place despite temperatures and small dilations ... I'm evaluating replace the bricks suspended plates expanded vermiculite (light, resistant up to 1200 ° C) or plates ceramic fibers (more resistant and somewhat heavier, endure about 1000 ° C in a continuous way) , I also have to assess the steel used in the outer structure to solidify the assembly and in some less hot spots ... I will keep you informed, I'd love to hear your opinion and advice to see if this winter I started. Greetings! 

How to solve the problems of sub-pressure: http://www.youtube.com/watch?v=0qu6EY4F7kI

Vermiculite plates Suppliers:
Suppliers ceramic plates 25 or 50 mm. thickness:
Refratermic  (about 35 € ceramic plate 1000x600x50 mm.)

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