[Stoves] Skirt design questions

[dstill at epud.net]

Dear Christa,

I very much look forward to discussing skirts, and stoves, and making everything
practical. I very much agree that things are only useful when they are used!

We are testing ideas for skirts now, in fact. What do you think about an
adjustable skirt with vertical spacers making a 10mm space that might work for a
variety of pots? The vertical spacer could be as high as needed to best contact
sides of local pots?

Also there is shape for the  stove top that acts like a skirt. So that directly
over the combustion chamber there is constant cross sectional area and the sides
of the top slope upwards creating a space maintaining cross sectional area( or a
little less?) closer to the sides of the stove top. This was developed by Dixon
Addair who worked for Belerieve Foundation, I think. It helps quite a bit.

Looking forward to learning from you.

Best,

Dean

Quoting Christa Roth <messinger.roth at africa-online.net>:

> Dear Dean, I don't think anybody questions the usefulness of skirts. The
> real question is how to make them practical for real users in real
> households out there who have dozens of different shapes and sizes of
> cooking pots, buckets and frying pans with and without handles and who
> want to use them all on ONE stove, because they have only space and
> resources to afford just that ONE stove. So if that one improved stove
> is not as convenient as the three stones they are using, they will keep
> on using the three stones because they can use them conveniently with
> any size and shape of pot....
> The challenge is to get from theory to practice without compromising too
> much on the efficiency. In other words: how wrong can you afford to have
> the gap and still get enough improvement on the heat transfer efficiency
> to justify the investment into a skirt at all....
> Let's discuss this further in Bangalore
> 
> Christa Roth
> Technical Advisor Malawi - Tanzania - Zambia
> Programme for Biomass Energy Conservation in Southern Africa
> 
> in Zambia: 
> c/o GTZ office, Private Bag RW37x, Plot No. 6469 Kariba Road, Kalundu,
> Lusaka
> Tel +260 1 2919 -18 / 19 / 20, Fax +260 1 291 946
>  
> in Malawi:
> c/o Info Centre for Food&Fuel Security Promotion Mulanje 
> P.O. Box 438, Mulanje, Malawi, Phone +265-1-466 279, Fax -466 435
> 
> Mobile Phones (only available when I am in the respective country):
> Zambia +260 97 207 870, Malawi +265 8 860 936, Tanzania +255 787 20 10
> 15
>   ----- Original Message ----- 
>   From: Dean Still 
>   To: 'Discussion of biomass cooking stoves' 
>   Sent: Thursday, February 22, 2007 6:14 PM
>   Subject: Re: [Stoves] Skirt design questions
> 
> 
>   Dear All,
> 
>   Skirts might be very helpful because by getting the gap right between
> the
>   skirt and the pot three good things could happen, I think:
> 
>   Increased velocity (better heat transfer to pot)
>   Control over excess air entering the combustion chamber (Higher Delta
> T plus
>   fewer emissions?)
>   Increased surface area of pot exposed to flue gases
> 
>   Getting increased velocity by decreasing constant cross sectional
> area,
>   higher temperatures due to less excess air entering the fire,
> improving the
>   heat exchanger (the pot), by using one short cylinder of sheet metal
>   definitely is interesting! We are trying .75 constant cross sectional
> area
>   now for the gap size. Then rate of burn goes down (less air) but time
> to
>   boil, fuel use, and emissions are decreased by about a third compared
> to the
>   same stove without a skirt.
> 
>   Best,
> 
>   Dean
> 
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