[Stoves] Stove testing methods

[Kevin Chisholm]

Dear David

Thank you for your note of Monday, October 02, 2006 9:23 PM. I would suggest 
that the "back and forth" states our respective views and approaches 
reasonably well.

Further to your original posting (copy below)...

1: Combustion Efficiency:
You can measure combustion efficiency by measuring the percentage of 
unburned fuel in the flu gas. Obviously, in a charcoal stove, the only 
significant unburned fuel would be CO. A CO meter, along with an air flow 
meter, would enable you to determine the weight of CO in relation to the 
charcoal being burned. From this, you could determine combustion efficiency. 
For biomass fuels that may have smoke and tars in the flue gas, you would 
need means of capturing them and analyzing them, and possibly Hydrogen, in 
relation to fuel burned.

(Note that "Combustion Efficiency" is very different from "Stove 
Efficiency". Combustion Efficiency deals only with the completeness of heat 
release from the fuel provided, while "Stove Efficiency" can be a 
combination of Combustion Efficiency and a measure of heat removed in 
performance of the desired task, or tasks. Stack temperature and % Excess 
Air are relatively important in the case of "Combustion Efficiency" but are 
very important in the case of Stove Efficiency)

2: Heat Transfer Efficiency is a measure of the percentage of available heat 
energy that is utilized in performing the desired "stove task". One must 
find a way to measure the heat energy transferred to the task. In the case 
where the task is boiling away water, this is relatively simple, in that 
"the formula" would be:
Heat Transfer Efficiency = (Heat transferred to the water that was boiled 
away as steam) / (Heat available in the products of combustion)

This does not account for shell losses from the stove to the surroundings. 
An internal calculation is necessary to account for possible losses due to 
combustion inefficiency.

Possibly a "Modified Stove Efficiency Test" would be best for your purposes? 
You could standardize on an excess air level that gave a Smoke Spot reading 
of #1, and then measure the CO2 in the flue gas, and the Flue Gas 
Temperature. This simple test would not account for heat losses from the 
furnace shell. What it does is indirectly measure the heat that was taken 
out of the products of combustion, but it does not give direct indication of 
how much of the available heat went to performing the desired stove task, 
and what percentage was lost to the surroundings from the stove shell.

If you outlined more specifically what you wishes to accomplish, then 
perhaps the List could offer specific suggestions.

Best wishes,

Kevin


 >>>>>>
>>>>>> ----- Original Message ----- From: "CEDESOL Foundation lists"
>>>>>> <lists.cedesol at gmail.com>
>>>>>> To: <frank at compostlab.com>
>>>>>> Cc: "Tessa Vlaanderen" <tessa.vlaanderen at gmail.com>;
>>>>>> <stoves at listserv.repp.org>
>>>>>> Sent: Friday, September 29, 2006 5:36 PM
>>>>>> Subject: Re: [Stoves] Stove testing methods
>>>>>>
>>>>>>
>>>>>>> Dear Stovers et al.,
>>>>>>>
>>>>>>> From the point of view of someone in the field, in a developing
>>>>>>> country, actively involved in stove dissemination, design and
>>>>>>> testing;
>>>>>>> more elaborate testing of fuels and such is not what is needed.
>>>>>>>
>>>>>>> Simplified testing procedures that can be reproduced in the lab in
>>>>>>> developed countries, in the lab in developing countries, combined
>>>>>>> with
>>>>>>> tests cooking local foods, combined with tests by actual users under
>>>>>>> their "normal" conditions is more practical for us.  That coupled
>>>>>>> with
>>>>>>> the scaling up suggestions offered by Don Oneal about a year ago
>>>>>>> is the
>>>>>>> most practical way to have a "generic" stove procedure.
>>>>>>>
>>>>>>> There are too many variables to take into consideration other
>>>>>>> wise. As
>>>>>>> I insinuated in my last post, with different cooking needs, fuel
>>>>>>> needs
>>>>>>> and cultures you just can not mechanize stoves and fuels so
>>>>>>> easily as
>>>>>>> some seem to be trying to do.
>>>>>>>
>>>>>>> 3 basic things are important to compare stoves.  How much
>>>>>>> pollution is
>>>>>>> produced and how much energy gets into the pot over time, plus
>>>>>>> how is
>>>>>>> the stove accepted by the actual users.  In the final analysis,
>>>>>>> the last
>>>>>>> variable is the most critical to getting stoves out of the designing
>>>>>>> labs and into the hands of the cooks.
>>>>>>>
>>>>>>> As a user in the field of the testing methods we welcome
>>>>>>> simplification
>>>>>>> on how to demonstrate combustion efficiency and heat transfer
>>>>>>> efficiency.  From there it is our responsibility to adapt to the
>>>>>>> users.
>>>>>>>
>>>>>>> thanks for the suggestions
>>>>>>>
>>>>>>> David Whitfield
>>>>>>> Cochabamba Bolivia
>>>>>>>
>>>>
>>>>
>>>
>>
>>
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