[Stoves] Request for help on TLUD operating data

Wed Aug 13 17:41:00 CDT 2014

Dear Ron

I happen to have some reasonably accurate mass change data sets that could provide grist for that particular mill. Your question really has two parts: how a stove design alters‎ the mass loss rate, and what happens at the end, or the trend, as it varies away from a straight line.

There is a moisture factor involved. It absorbs heat reducing the pyrolysation rate only so long as it is present so at the end there is a puff of rapid devolatilisation from the 'last bit' of fuel after it dries.

Unless the stove had a very high superficial velocity a char making or burning stove would still exhibit the curve up to the point at which char burning commences. Are you OK with working from the initial part of the curve? The performance should be 'characteristic'.

The mass loss curve could be moisture compensated quite easily.

Regards
Crispin

BBM 2B990AFA
From: Ronal W. Larson
Sent: Thursday, August 14, 2014 04:40
To: Discussion of biomass
Reply To: Discussion of biomass cooking stoves
Subject: [Stoves] Request for help on TLUD operating data

List:

        I am trying to better understand TLUDs - for purposes of improving their performance.  This is to ask all char-making stove developers to report back, either on-list or off-list, on a fundamental characteristic of all TLUDs: the way performance changes over time.

        I have seen plots showing the weight of the stove-fuel combination; basically dropping relatively linearly as the pyrolysis front moves from top to bottom.  My question is on the word “relatively”.  Is that weight loss at the end dropping more (concave down) or less (concave up) rapidly than linearly?

Stated as an equation, for a test run with a single fuel and a single primary air center the average linear equation could be:

        W(t)= Wo-A*t, with A = (W(t=tf)-W(t=o))/tf

but what I need is a quadratic form:

        W(t) = Wo - B*t + C*t^2

where B is certainly positive, but equal to A only if C is zero.

C can be either positive (concave up) or negative (concave downward).   The sign of C is the most important question I am asking - but even an approximate ratio C/B would be a big help.

        I only need a rough plot of the weight - then I can come up with the A,B, C constants.  I for sure need the starting and ending weights, and then at least a few other weights (and their times) near the end.  Knowing more on the stove would be helpful - especially the fuel can diameter.  The fuel  (sticks, chips, pellets, etc) is needed also.

Who can help?  (and leads to published material would be just as good.)

I will summarize and report - and can do this without using any names.

Ron

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