[Stoves] LannyPan cooking module and the TLC burner

[Alex English]

Lanny,
I think you said that you were using oak blocks of wood. What type?  The 
heart wood of most of the white oaks have pores filled with tylose which 
prevents the ingress of water and decay agents, while the red oaks 
don't. I expect you would see quite a difference in their rate of 
re-hydration even when submerged.

Alex

On 11/08/2013 7:31 AM, ajheggie at gmail.com wrote:
> [Default] On Sat, 10 Aug 2013 16:10:56 -0400,"Lanny Henson"
> <lannych at bellsouth.net> wrote:
>
>> It does take a long time for dry wood to totally absorb water but 50 min is
>> not insignificant,  and concrete block soaks up water a lot faster.  I am
>> thinking that even the water on the surface of wood or even dry wood is a
>> problem for most top lit batch burners.
> Yes anything that robs the pyrolysis front of heat will compromise a
> TLUD burn. As has been shown in the past primary air has to increase
> to provide oxygen to burn nascent char to provide the heat to drive
> off moisture, such that at 25%mc there is no residual char.
>
>> Green wood is a problem, it stinks up the place and smuts the pot but it
>> will still burn fresh green wood after the fire heats up. Green wood
>> probably takes away more energy than it provides but it will burn fist size
>> chunks.
> Yes but this is the acid test, it takes a lot of time and energy to
> get heat into the middle of a bit of green wood to drive off the
> moisture which is why solar/air drying is very useful even if slow.
>> I will weigh the wood before and after soaking next time.
> Good
>> How much moisture content is the break even point?
> Theoretically we can postulate that you need about 0.75kWh(t) to drive
> off 1kg of water and raise it to flue exhaust temperature, this is
> energy lost. Each kg of dry wood burned completely will yield about
> 5kWh(t) so the break even point is when the energy content of the wood
> equals the energy loss of the vapour. This point is 86% moisture
> content. Of course in practice this is unattainable and even on the
> industrial scale sustaining combustion at more than 66% (green poplar
> or spruce) is difficult and will not be clean. The reason is that the
> combustion chamber cannot ever get hot enough for a clean burn with
> high moisture content fuel, the char will burn out but the offgas
> never gets hot enough to sustain a flame.
>
> AJH
>
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