[Stoves] Designs

[Tom Miles]

Thanks to Dr. Mukunda for providing his 1988 paper on the Swosthee stove,
"Portable single-pan wood stoves of high efficiency for domestic use" (2 MB
pdf) which we have made available on the Stoves website at:

http://bioenergylists.org/en/mukunda1988

Tom Miles

  

-----Original Message-----
From: stoves-bounces at listserv.repp.org
[mailto:stoves-bounces at listserv.repp.org] On Behalf Of Mukunda
Sent: Monday, August 07, 2006 7:44 AM
To: stoves at listserv.repp.org
Subject: Re: [Stoves] Designs

Dear Dr. Tom Miles,

<snip>
Regarding the Swosthee stove about which you have specific questions - About
a thousand were built during 1990 - 1884 and field tested. The key problem
has been the life of the stove. Because the inner metal walls experience
temperatures of 750 to 1000 C, the hardware lasts only a few months. One of
the key things that we uncovered in this period was that we cannot get
higher effioiencies unless the air-to-fuel ratio is close to stoichiometric
value. It was also clear that any of the stoves that utilized free
convection process for delivering the air won;t be able to maintain the
correct air-to-fuel ratio for the duration of the operation of the stove.
This is the reason that further development in this direction was not
pursued, We examined the possibility of using a fan to deliver the air, some
thing that we did in laboratory experiments to determine the role of
air-to-fuel ratio. Unfprtunately, during 1990 to 1994, there was no cheap
harware for delivering the air at a fixed flow rate. And even after we saw
the fixed fuel stove with Dr. thomas Reed in
1996 or so, we could not identify for a long time a reasonable source of
fans. It is only in the last three years that computer fans that are really
cheap have arrived in the market. This as given life to the reverse
downdraft stoves all over the place. We have done some serious scientific
study over the last four years and uncovered features of the stove that will
give high efficiencies. We have been able to get up to 55 % thermal
efficiency through various optimization strategies. We are still exploring
how to get up to values in excess of 60 % particularly because the kerosene
and gas stoves promise 70 to 75 % efficiency. This has ben our aim over the
last twentyfour years.