[Stoves] Bangladesh TLUD (was Re: No subsidies in TLUD char peoduction

Sat Dec 9 22:42:32 CST 2017

Dear Nikhil

I recall he used the WBT of the day, probably WBT 3.1. I recall the values for the light insulative ceramic chamber was 22% and the heavy heat conductive chamber was 24% and he got a repeatedly higher value for the heavy conductive chamber.

I have concluded the reason for this enhanced performance is to be noted late in the fire when the heat stored in the combustion chamber is returned to the fire as it wanes. It keeps the CO burning for longer late in the fire providing heat otherwise lost (chemical loss).

An insulative chamber provides a hotter chamber sooner but this advantage is soon lose when heat migrates into the stove body and cannot return later at a rate sufficient to keep the chamber wall hot.

>What he discovered is similar to common knowledge from my childhood - in samovars for heating bathwater. Designs with thicker copper retained heat better and fuel efficiency was higher; which mattered because in the city we used purchased charcoal.

So where fuel is purchased there is a direct consequence for higher or lower fuel efficiency.

>If you standardize the cooking experience and cooking behavior, I suppose you can adjust for the amount of heat that goes in the stove body but is not utilized for cooking experience.

Ah, wait a minute. You have moved from assessing the performance of a defined system to assessing one aspect of its internal sub-systems revealed in:

>And if you were to do that, you would come up with some computation of efficiency. Which I call "competing on fuel efficiency percentages is infantile business" because standardizing cooking behavior and cooking experience is infantilism.

This completes the switcheroo. You have picked on the standardisation of a ‘behaviour’ (which I call a ‘burn sequence’) and criticized the metric used to rate the performance of the whole system in use, but your family.

>That has nothing to do with whether fuel efficiency matters or dominates consumer choice.

That is a question outside the cooking system, residing entirely between the ears of the user. To optimise the performance on any metric of choice of feature, one often standardises the task to isolate the how one factor contributes to the overall performance.

Standardising everything, as in a WBT performed by Aprovecho using their ‘standard fuel’ is a way to compare labs, and is used by the ISO in their determination of a lab’s ability to replicate results. To get ISO 17025 certification, a lab has to replicate the results of another lab (save in one special case).

>Testing and metrics ought to have a purpose.

They do, and they have two broad categories of purpose: the determination of the performance on a sub-system metric, and their performance as a system. There is no point in reporting the performance of a system on the basis of how one of its sub-systems rates.  Such sub-categories of performance may be interesting, such as the kW of heat generated per cubic foot of combustion chamber. That is a metric in the current National Standard of Mongolia for low pressure boilers. It is not a system performance metric, but it is required for reporting purposes. IT is an example of the design engineer’s interests leaking through to the final product. The fuel consumption, fuel flexibility, emissions, whatever might be a systems rating, is not improved by requiring such a metric, even though the engineers determine and track such arcane things.

Fuel consumption is such a primary aspect of system performance it is worth including it even when the fuel in some communities is unlimited and freely available. This does not apply in most communities, or any community where effort is considered a cost.

Regards
Crispin in the snow today
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