[Stoves] Practical Stoves- Introducing The Versatile Stove

[ajheggie at gmail.com]

[Default] On Sat, 5 Nov 2016 07:58:47 -0700,kgharris
<kgharris at sonic.net> wrote:

>AJH, Dale, and All,
>
>Thank you, this is good to know.  The problems that you point out make good
>sense.
>
>Dale appears to have found a way to dry the wood in the fire, I think by
>keeping the overall fire large (a benefit of the large combustion chamber),
>compared with the evaporating water (the larger dry wood compared to the
>smaller wet wood).  Thus the water is evaporated at a slower rate that the 
>fire is able
>to handle.  Under stressed circumstances this would make wet wood available
>to burn right away, though the emissions may suffer.  I am looking forward
>to hearing more about this stove as it progresses.  Versatility seems like a 
>good approach.


Kirk I do not have any flue gas analysers so I have nothing to measure
what the effects are but many years ago I built a large wood burner
and we tested its CO content at 30 parts per million , it would burn
woodchip at 50% MC if it first got up to temperature on dry wood. I
surmised that the negative feedback of the  water reducing combustion
chamber temperature meant that  it just never got hot enough to
cleanly burn and much of the wood's calorific value was lost in the
smoke. If it was once up to temperature then all the gas burned and
contributed to keeping the combustion chamber hot enough to burn
cleanly. With wet wood this temperature seemed to be around 800C.  Now
wood has an adiabatic flame temperature of over double that and we did
see temperatures of 1200C with dry wood so it might be possible to add
a little damper wood whilst keeping an eye on the flue temperature.

So as long as the average water content is low enough that the overall
temperature is high enough to allow complete combustion...

With larger chip stokers that are designed to burn 45%mc wood they use
various techniques for keeping the firebox temperature up, like
refractory liners and pre heating the combustion air. These aren't
possible without chimneys or fans so  it makes better sense to stick
with dry wood.


Bear in mind the smaller a stove gets the higher the surface area the
combustion chamber has to lose heat through the sides, so it is easier
to keep a big stove hot enough, at the cost of burning more fuel.

AJH