[Stoves] Thermal efficiency

Crispin Pemberton-Pigott crispinpigott at gmail.com
Wed Apr 18 07:42:23 CDT 2012


Howzit Cedosol?

The protocol was a SeTAR Thermal Efficiency Test Protocol which is very
similar to the EN:521:2006 test which is used in India.

Basically it is the thermal efficiency test applied to a non-condensing heat
exchanger.

The difference is that the Indian tests does not check for evaporated water
during the temperature rise. Also the range we use starts higher (to ensure
there is no water remaining on the underside of the pot) and finishes sooner
(to ensure that nearly no water evaporates while heating. The Indian pot is
heavier, perhaps cast?

Both use the thermal mass of the pot as part of the calculated heat gained
by the pot. There is not complete agreement on this, some feeling that the
pot is 'part of the stove structure' and others feeling that it is heat
transferred by the gases so it deserves to be credited. We therefore report
both. The difference is about 2% @ 65% efficiency.

Given the subtle differences in the tests the agreement on the efficiency
for the same product is goof.

Regards
Crispin

-----Original Message-----
From: stoves-bounces at lists.bioenergylists.org
[mailto:stoves-bounces at lists.bioenergylists.org] On Behalf Of CEDESOL
Foundation
Sent: Wednesday, April 18, 2012 2:37 PM
To: Discussion of biomass cooking stoves
Subject: Re: [Stoves] Thermal efficiency

What was the test protocols?  Greetings Chrispin.

On 4/17/12, Crispin Pemberton-Pigott <crispinpigott at gmail.com> wrote:
> Dear Friends
>
>
>
> We have been conducting a series of thermal efficiency tests on three 
> stoves, more than 50 altogether, and I am sharing a consistently good 
> result from two of them. Here is one:
>
>
>
> Thermal Efficiency
>
>
> 66.7%
>
> 67.1%
>
>
> 67.1%
>
>
>
>
> 67.6%
>
>
>
>
>
> That was achieved at about 2 kW power level.
>
>
>
> The other was at a similar level:
>
>
>
> Thermal efficiency
>
>
> 73.0%
>
> 71.3%
>
>
> 70.8%
>
>
>
>
> 69.9%
>
>
>
>
>
> I am pretty sure I have not seen this for a high power level before. 
> Very low power can achieve high efficiencies but it is not a very useful
heat.
> With these two we are seeing 1.4 kW absorbed into the pot. Pretty 
> impressive.
>
>
>
> I will ask permission to share the data for what will be 69 tests in all.
>
>
>
> One set involved repeating a test done in another country with a 
> similar though not identical protocol. The result was within 2.3% so 
> the approaches are getting comparable results. Given that the fuel was 
> not identical, altitude difference and not exactly the same pot, the 
> difference is negligible.
>
>
>
> Other lab (recalculated to correct a minor error)
>
>
> 69.4%
>
> 69.4%
>
>
>
> SeTAR Lab with a slightly smaller pot and 1.1 litres less water in it
>
>
> 66.7%
>
> 67.1%
>
>
> 67.1%
>
>
>
>
> 67.6%
>
>
>
>
>
> It is nice to see this performance level achieved consistently. We are 
> seeing a consistent performance variation with pot diameter: bigger is 
> better.
>
>
>
> Regards
>
> Crispin
>
>
>
>

--
Sent from my mobile device

David Whitfield V.
Executive Director
CEDESOL Foundation

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