[Stoves] big TLUD

Crispin Pemberton-Pigott crispinpigott at outlook.com
Wed May 20 14:30:37 CDT 2015


Dear Rolf

I have a general rule (which results from empirical testing) which is that
the fuel particle has to be smaller than 1/6th of the diameter of the
chamber. At 6 it is iffy - problems abound with the fire going out and
difficulty igniting, high excess air, poor potential for secondary air
management etc.

There is an upper limit too but I am not sure where it is. It is less than
25 and I suspect above 20 is a cause for concern. 

Packing density is an issue but it is an indicator, but 'the issue'.  "The
issue" is the superficial and actual velocity of air moving through the
system.

The numbers are influenced by the temperature of the surrounds so it is not
as simple as saying 'here are the hard numbers'.  When you get to mixing
different sizes together you will have to work with the actual air flow
rate.

Regards
Crispin
.

Hallo "big TLUDers",

as I see from the various experiences and comments, the cross section of a
big TLUD is to some extent limited.
That means that in order to build a bigger unit, it has to grow by lenght,
which in turn must enhance the resistance to the primary air flow. From
Imberts we know that the relation between fuel size and hearth or throat is
crucial.
There must be enough space left between the particles to allow for a
adequate air/gas flow.

My question: Does anyone have a clue on the matter of fuel size in TLUDs ?

Is it possible that larger diameters ask for larger chunks which in turn
provide more space between them and ideally spread the upflowing air more
uniformly?

Rolf




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