[Stoves] TLUD Syngas Flame and the Red-Hot Chimney in a Kerosene Heater.

Philip Lloyd plloyd at mweb.co.za
Tue Apr 8 01:07:02 CDT 2014


You don't seem to understand how these things work.

 

In operation, the two chimneys glow red-hot.  The radiant heat evaporates
kerosene from the glass-fibre wick, and the hot vapours rise and are mixed
with air coming in through the holes - which of course is pre-heated.
Combustion take place in the annulus.  As the mixture rises, you even get
some secondary air combustion effects quite high in the chimney - under some
conditions you can see blue flames going inwards from the holes.

 

When first lit, the chimney pieces are still cold, and you get a rather
dirty diffusion flame until the radiant-heat evaporation of the kerosene
occurs.  The reverse can happen on switching off - the chimney pieces are
still hot and kerosene continues to evaporate from the retracted wick and
gives a "tracer flame" which takes some time to go out.

 

The thermal loss by radiation is what reduces the efficiency of this design
when used as a cookstove to the order of 30-35%. Of course, in a heater this
is no loss.  In the design you have to be careful to shield the fuel tank
from heating by radiation and conduction; in some designs of cheap
cookstoves, this feature is ignored, and if used for more than about 30
minutes the fuel can heat to above its flash point.  When that happens, even
knocking the stove can lead to catastrophic fires - we measured one burning
at over 1MW! It can lead to indoor air temperatures exceeding 400 deg C
within a minute.

 

The chimney pieces are quite thin to reduce their thermal mass and so reduce
the time it takes to heat them up when starting the appliance - or cooling
down when switching off.

 

Prof Philip Lloyd

Energy Institute

Cape Peninsula University of Technology

PO Box 652, Cape Town 8000

Tel:021 460 4216

Fax:021 460 3828

Cell: 083 441 5247

 

 

From: Stoves [mailto:stoves-bounces at lists.bioenergylists.org] On Behalf Of
Julien Winter
Sent: 08 April 2014 01:48
To: Discussion of biomass cooking stoves
Subject: [Stoves] TLUD Syngas Flame and the Red-Hot Chimney in a Kerosene
Heater.

 

Hello stovers;

 

I took my  Kero-Sun Radiant 10 apart.  There are some photographs of the
inner and outer chimneys in the attached pdf.

 

The inner chimney as baffles at the bottom and is enclosed, with
perforations at the top.

 

For sport, I put the inner chimney, and then the inner chimney nested in the
outer chimney on top of a 7.5 cm diameter natural draft TLUD.  As we might
expect, it created resistance to exhaust gas flow, that reduced the
secondary uptake, and caused the TLUD to emit a small amount of visible
smoke.   I did this in daylight, so I don't know if any of the chimney
assembly became red hot.

 

In order to investigate this properly, I would have to destroy the chimneys
by breaking off the baffles, and expanding the diameter of the perforations
in the chimney walls --- and I am not prepared to do that.  What is needed
is to find a kerosene heater wreckers yard to scavenge bits.

 

Thus, it is still an open question (for me anyway) if something like the
chimneys in kerosene heaters, or a type of catalytic converter, can reduce
soot production from natural draft TLUDs.

 

Cheers,

Julien

 

 


-- 

Julien Winter
Cobourg, ON, CANADA

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.bioenergylists.org/pipermail/stoves_lists.bioenergylists.org/attachments/20140408/ff1d51c8/attachment.html>


More information about the Stoves mailing list