<html><head><style type='text/css'>p { margin: 0; }</style></head><body><div style='font-family: Arial; font-size: 12pt; color: #000000'>A.D: and list<br><br> Thanks very much. I vaguely recall similar numbers - maybe from Dean Still. The first time I saw a theory on these "convection shields" was in a doctoral dissertation or maybe a USAID technical report by Dr. Sam Baldwin. Has anyone on this list a copy of that? and/or seen a theoretical treatment?<br><br>Ron<br><br><br><hr id="zwchr"><b>From: </b>"Anand Karve" <adkarve@gmail.com><br><b>To: </b>"Discussion of biomass cooking stoves" <stoves@lists.bioenergylists.org><br><b>Sent: </b>Sunday, July 31, 2011 9:14:32 PM<br><b>Subject: </b>Re: [Stoves] Improve gas burners efficiency?<br><br>Dear Ron.<br>the gap width between the pot and the jacket surrounding it was<br>determined by trial and error. We have not kept the data of these<br>trials. Also, when these cookers are fabricated, the fabricators often<br>face difficulties in adhering to the exact specifications. So the<br>cookers being offered to users have gaps ranging approximately between<br>0.5 and 1 cm between the cooker and its jacket.<br>Yours<br>A.D.Karve<br>On Sun, Jul 31, 2011 at 9:15 PM, Ron Larson <rongretlarson@comcast.net> wrote:<br>> A D:<br>><br>> Can you provide more data on the optimum gap width for your Serai cooker?<br>><br>> Ron<br>><br>> Sent from my iPad<br>><br>> On Jul 31, 2011, at 12:19 AM, Anand Karve <adkarve@gmail.com> wrote:<br>><br>>> Dear Xavier,<br>>> we have worked with skirtings around pots. They work best, if they are<br>>> pot-specific. Our Sarai cooker uses just 100 g charcoal to cook rice,<br>>> beans and vegetables (or meat) for a family of 4 to 5 persons. The<br>>> entire cooker is surrounded by a stainless steel sleeve, which directs<br>>> the hot flue gases to flow through the gap between the cooker and the<br>>> sleeve. The efficiency of the cooker is increased because all the flue<br>>> gases remain in contact with the entire outer surface of the cooker.<br>>> If the cooker is used without this jacket, it requires at least 4<br>>> times as much fuel to cook the same quantity of food. Jackets can be<br>>> designed for pots in restaurants, where they generally have a standard<br>>> pot for each function (a specific pot for rice, another for<br>>> vegetables, and still another for deep frying etc.) But in a<br>>> household, where the housewife may be using at least 20 to 30 pots of<br>>> different sizes, it would cost a lot of money to make sleeves for each<br>>> pot.<br>>> Yours<br>>> A.D.Karve<br>>> On Sat, Jul 30, 2011 at 2:59 AM, Xavier Brandao <xvr.brandao@gmail.com> wrote:<br>>>> Dear stovers,<br>>>><br>>>><br>>>><br>>>> When promoting the institutional rocket stoves in public administrations<br>>>> kitchens, restaurants, hotels in South Benin, mostly in the cities of<br>>>> Cotonou and Porto-Novo, I am told more than once that wood is not used<br>>>> anymore, because of the smoke, the cost, or the hassle. Many moved to gas<br>>>> burners, which is of course great. We produce and sell wood stoves, but we<br>>>> always encourage people to use gas cookers, because they are cleaner, more<br>>>> ecological and economical. We only produce wood stoves for people who would<br>>>> have use wood for cooking anyway (for certain dishes, certain quantities, or<br>>>> in certain big institutions).<br>>>><br>>>><br>>>><br>>>> Many people liked the sturdy design of the stoves and asked if they could<br>>>> have the same for gas stoves. I always reply that is was designed for wood<br>>>> only, and promise we’ll think about a model for gas burners.<br>>>><br>>>><br>>>><br>>>> My question is: how much can a gas burner be improved in terms of energy<br>>>> efficiency? Is it worth spending metal in making a skirt around the burner<br>>>> and the pot? I was thinking also of a surface under the burner, perhaps just<br>>>> like the institutional stoves, made of a mix of clay, to radiate heat<br>>>> upwards. It would give a traditional look to a modern cooking device.<br>>>><br>>>><br>>>><br>>>> My quick calculations showed it could cost in the very very worst case up to<br>>>> 30 000 CFA francs all included (about 45 euros) for a skirt for one burner.<br>>>> People seem to be ready to pay that, if it means savings. A lady who runs a<br>>>> restaurant paid a welder 60 000 CFA for two skirts, which amusingly enough<br>>>> is in line with my calculations. They are not made yet, I’m curious to see<br>>>> how they look.<br>>>><br>>>><br>>>><br>>>> Here is a picture of the burners:<br>>>><br>>>> http://imageshack.us/photo/my-images/803/rimg1222.jpg/<br>>>><br>>>> Another burner, inserted in a truck rim:<br>>>><br>>>> http://imageshack.us/photo/my-images/834/rimg1229.jpg/<br>>>><br>>>> Here is a picture of a small burner, with a small skirt which only protects<br>>>> the flame from wind, not the pot:<br>>>><br>>>> http://imageshack.us/photo/my-images/38/rimg1228.jpg/<br>>>><br>>>><br>>>><br>>>> I’ve searched a bit on Bioenergylist, and in Micro Gasification Cooking with<br>>>> gas from biomass, I could only find the Vesto stove as a gas stove with a<br>>>> skirt.<br>>>><br>>>><br>>>><br>>>> This post brings another question, which I will detail in another issue.<br>>>><br>>>><br>>>><br>>>> Thanks in advance,<br>>>><br>>>><br>>>><br>>>> Xavier<br>>>><br>>>> _______________________________________________<br>>>> Stoves mailing list<br>>>><br>>>> to Send a Message to the list, use the email address<br>>>> stoves@lists.bioenergylists.org<br>>>><br>>>> to UNSUBSCRIBE or Change your List Settings use the web page<br>>>> http://lists.bioenergylists.org/mailman/listinfo/stoves_lists.bioenergylists.org<br>>>><br>>>> for more Biomass Cooking Stoves, News and Information see our web site:<br>>>> http://www.bioenergylists.org/<br>>>><br>>>><br>>>><br>>><br>>><br>>><br>>> --<br>>> ***<br>>> Dr. A.D. Karve<br>>> President, Appropriate Rural Technology Institute (ARTI)<br>>><br>>> *Please change my email address in your records to: adkarve@gmail.com *<br>>><br>>> _______________________________________________<br>>> Stoves mailing list<br>>><br>>> to Send a Message to the list, use the email address<br>>> stoves@lists.bioenergylists.org<br>>><br>>> to UNSUBSCRIBE or Change your List Settings use the web page<br>>> http://lists.bioenergylists.org/mailman/listinfo/stoves_lists.bioenergylists.org<br>>><br>>> for more Biomass Cooking Stoves, News and Information see our web site:<br>>> http://www.bioenergylists.org/<br>>><br>><br>> _______________________________________________<br>> Stoves mailing list<br>><br>> to Send a Message to the list, use the email address<br>> stoves@lists.bioenergylists.org<br>><br>> to UNSUBSCRIBE or Change your List Settings use the web page<br>> http://lists.bioenergylists.org/mailman/listinfo/stoves_lists.bioenergylists.org<br>><br>> for more Biomass Cooking Stoves, News and Information see our web site:<br>> http://www.bioenergylists.org/<br>><br>><br><br><br><br>-- <br>***<br>Dr. A.D. Karve<br>President, Appropriate Rural Technology Institute (ARTI)<br><br>*Please change my email address in your records to: adkarve@gmail.com *<br><br>_______________________________________________<br>Stoves mailing list<br><br>to Send a Message to the list, use the email address<br>stoves@lists.bioenergylists.org<br><br>to UNSUBSCRIBE or Change your List Settings use the web page<br>http://lists.bioenergylists.org/mailman/listinfo/stoves_lists.bioenergylists.org<br><br>for more Biomass Cooking Stoves, News and Information see our web site:<br>http://www.bioenergylists.org/<br><br></div></body></html>