[Stoves] Chris Bradnum's stove makes an appearance

Thu Mar 13 12:03:11 CDT 2014

Dear Ron

The article was less technically correct that it first appears - that's why
I said not to take number too seriously.

If the CO/CO2 ratio is the metric used to define combustion inefficiency,
then yes it is quite possible for a fire, from ignition to extinguishing, to
have an average ratio of 10%. The problem is people report all sorts of
mismatched metrics so one has to never accept something at face value. It
was good you asked what the efficiency definition was. That is the right
question. I would have given different answers to the question about average
CO/CO2 ratios for average (baseline) stoves.

The efficiency reported in the article is completely backwards. Chris was
talking about the combustion efficiency metrics which is an inefficiency and
the author thought it means the cooking efficiency or something.  

I checked on of the HPT test results and I hope Chris is OK with me
reporting it was 30% and that was the overall system efficiency. That is
calculated as: the energy accumulated in the pot divided by the energy
theoretically available from the mass of fuel consumed during the whole burn
cycle. The heat transfer efficiency is of course higher than that.

I only checked one of many tests so I won't report anything else. I just
want you to know where the fuel saving number came from, correcting the
misinformation in the published article.

Other biomass stoves emerging from South Africa make similar claims: Rocket
Works 38% and Vesto 35% calculated on the same basis and burning the same
fuel (Black Wattle).

Regards
Crispin

From: Ronal W. Larson [mailto:rongretlarson at comcast.net] 
Sent: Thursday, March 13, 2014 12:25 PM
To: Crispin Pemberton-Pigott; Discussion of biomass
Cc: Bradnum, Chris
Subject: Re: [Stoves] Chris Bradnum's stove makes an appearance

Crispin:  (adding Chris (with acknowledgement of a message) and List)

            Assuming that the "in" in inefficiency just got lost, is a 10%
combustion inefficiency conceivable (or normal) for a rocket type of wood
stove?

Ron

On Mar 13, 2014, at 6:41 AM, Crispin Pemberton-Pigott
<crispinpigott at gmail.com <mailto:crispinpigott at gmail.com> > wrote:

That test was probably the heat transfer efficiency - I will have to check.
The product was in the development phase but it may have been the overall
system efficiency. 

The article called the combustion inefficiency the combustion efficiency.
Don't take any of the numbers too seriously. 

Regards 

Crispin 

BB10 Rocks!

From: Ronal W. Larson

Sent: Wednesday, March 12, 2014 23:59

To: Discussion of biomass; Crispin Pemberton-Pigott

Subject: Re: [Stoves] Chris Bradnum's stove makes an appearance

Crispin  cc list

  Can you explain the efficiency definition that is being used at UJ?

Ron

On Mar 12, 2014, at 9:04 PM, Crispin Pemberton-Pigott
<crispinpigott at outlook.com <mailto:crispinpigott at outlook.com> > wrote:

> Dear Friends 
> 
>
http://www.engineeringnews.co.za/article/uj-develops-energy-efficient-stove-
for-low-income-households-2014-03-12/rep_id:3182
> 
> This is not a technically exact report but there is not really any bad
publicity for improved stoves.  
> 
> Well done Chris.  
> 
> Regards 
> Crispin 
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